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4
Design for a National Health
Care Data System
The foregoing discussion makes it clear that the panel believes that
existing data systems are not adequate to yield the range of statistical infor-
mation needed to fully address the complex health care issues facing this
nation. NCHS has proposed a general strategy to expand and extend its
provider-based surveys to be more responsive to data needs and has taken
the first steps toward geographically integrating them with the National
Health Interview Survey (NfIIS). These proposed changes, however, do not
satisfy the urgent needs for data to monitor the health care of the nation.
The panel's appraisal has demonstrated that, as currently conceived, the
center's plan does not provide the capacity to address important questions
about the interrelationships between the health status of individuals and the
patterns and cost of health care services they receive from a broad range of
providers and service settings over time. The long-term agenda, therefore,
requires consideration of further, more fundamental restructuring.
Since a design is dictated by the objectives of a data system, this chap-
ter first briefly states the panel's perception of the objectives of a National
Health Care Data System and then presents the panel's recommended de-
sign framework for achieving these objectives. The benefits and limitations
of the proposal are discussed, and issues that require further research are
identified in the discussion. The chapter concludes with a suggested imple-
mentation schedule.
62
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DESIGN FOR A NATIONAL HEALTH CARE DATA SYSTEM
STATEMENT OF OBJECTIVES
63
The objectives of the National Health Care Survey proposed by NCHS
should be driven by the goals and objectives of the nation's health care
system, a primary goal of which is to deliver health care services effectively
and efficiently to the entire U.S. population. A simple statement then of the
objectives of a National Health Care Survey would be to provide statistics
on a continuing basis that reflect the condition of health care in the United
States, particularly with respect to the critical issues of access, quality, and
cost. Such a survey should have the capability of obtaining data related to
the characteristics and health status of individuals and their demand for, and
use of, health care over time and across a broad range of providers and
service settings that can be linked at the individual rather than the aggregate
level. Data are needed to support analysis along each of the following
. .
dimensions:
Access: there is need for information on the supply of health care
providers (including information on numbers, distribution, and type)
and the demand for and utilization of health care services by specific
segments of the population (e.g., racial and ethnic minorities, migrant
populations, the uninsured, the elderly, the disabled) and by other char-
acteristics such as health care insurance coverage status.
Quality: there is need for information concerning the health and func-
tional status of the patient prior to and after treatment, the appropriate-
ness of treatments or procedures provided, the degree to which health
care providers resolve problems, and the satisfaction of the patient with
the process.
Cost: there is need for information on expenditures for health care
services by type of provider, the cost of treatment for an episode of
illness for a specific diagnosis, its distribution among provider types,
and the source of payment for care provided, including how much is
paid by insurance and how much is paid out-of-pocket.
In addition to obtaining information from providers, information is needed
about health care consumers. For example, if a consumer has had contact
with several provider types for a given episode of illness, some way has to
be found to obtain that information in a coordinated way. Some people may
have had no contacts with the health care system at all; this group is impor-
tant to identify, and information is needed on their health care needs. For
example, answers are needed to the following questions concerning the
health care of consumers:
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TOWARD A NATIONAL HEALTH CARE SURVEY
.
What is their health status, in terms of disability, functional status,
and chronic conditions?
What are their unmet health care needs? What are the individual's
perceptions regarding access to health care?
What is the person's health insurance coverage, including no cov-
erage at all?
What is the person's use of health care providers over a defined
period of time? For each episode of care? For what conditions?
At what cost, both out-of-pocket and covered by insurance?
What are the person's knowledge, attitude, and practices related to
health promotion and disease prevention, such as knowledge of risk
factors, attitudes toward risks, and risk behavior?
What are the person's demographic characteristics?
No one single survey can provide answers to all these questions. An
integrated data system is needed with linkage capability at the individual
level that includes a variety of approaches, including surveys of specific
provider types and service settings, follow-up of patients seen for specific
conditions by specific types of providers in specific settings, longitudinal
surveys of the household and nursing, home populations, and possibly sur-
veys of episodes of illness.
In addition, there is need for improved collaboration, coordination, and
integration of health care data collected by NCHS and other agencies of the
Department of Health and Human Services. Care should be taken to ensure
that health care surveys carried out by NCHS and the other agencies use
standard definitions and classifications and do not unnecessarily duplicate
information and that other needed steps are taken to facilitate integration of
data sets for analysis and dissemination.
DESIGN CONSIDERATIONS
The panel was guided by three basic considerations in proposing a
design framework for a National Health Care Data System:
(1) Any design proposed has to meet existing information needs, espe-
cially those currently not being met, such as those identified in
Chapter 2.
iSome of the methodological issues associated with accessing, linking, and integrating data
sets are discussed in Wachter and Straf (1990).
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DESIGN FOR A NATIONAL HEALTH CARE DATA SYSTEM
65
(2) As the nation's health care system changes, so too will the informa-
tion needs that give the system direction. The design for the Na-
tional Health Care Data System must therefore possess sufficient
flexibility to be capable of responding in a timely manner to chang-
ing information needs. This flexibility should include the capabili-
ty to use special supplements to ongoing surveys to quickly provide
data in support of emerging information needs and to support the
conduct of ad hoc special studies.
(3) The design proposed should minimize any disruption to the current
NCHS survey program to facilitate implementation of any opera-
tional changes for NCHS that the design might require and, as far
as possible, preserve continuity between existing and new data out-
puts.
A FRAMEWORK FOR A NATIONAL HEALTH
CARE DATA SYSTEM
With the above design considerations driving its thinking, the panel has
proposed a design strategy to meet the various data needs that have been
identified in its deliberations. Some of the currently unmet needs relate to
cost of care for patterns of illness, outcomes, and patterns of provider utili-
zation during an illness, access to provider care, functional status, severity
of illness prior to and after treatment, insurance coverage, information about
specific population subgroups (e.g., racial and ethnic minorities, migrant
populations, the uninsured, the elderly, the disabled), as well about other
categories (such as providers not currently covered by NCHS provider sur-
veys and rare illnesses).
As stated in the preceding chapter, the event-based follow-up design
proposed by NCHS, as an extension of existing NCHS provider surveys,
would allow NCHS to expand its provider-based data gathering to include
outcomes of hospital and private practice physician care, two important and
currently unmet data needs. There are major issues, however, surrounding
feasibility, operating procedures, and informed consent that need to be re-
solved before the design could be implemented.
Certain important data needs remain unmet with the adoption of the
event-based follow-up design. Some examples are the ability to produce
person-based estimates of illness, access to care, patterns of care for epi-
sodes of illness, and associated costs. Still needed, therefore, is a broader
strategy that addresses these unmet data needs in an effective manner.
Such a strategy is presented below, not so much as one specific design
but as a design framework for a National Health Care Data System within
which a variety of survey approaches linked to the NHIS can be developed,
~.,
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TOWARD A NATIONAL HEALTH CARE SURVEY
and from which a broad range of health-related information needs can be
met. The panel believes that, taken as a totality, its recommended course of
action represents the long-term direction in which the National Health Care
Data System should evolve.
Although NClIS has taken the first important steps to expand on the
coverage and content of the provider surveys and geographically linking the
provider surveys with the National Health Interview Survey sample design,
in the panel's judgment the NCHS has not gone far enough. The panel pro-
poses in this chapter a comprehensive approach for the National Health Care
Data System that goes beyond the expansion planned by NCHS and that links
the design and operation of the National Health Interview Survey with the
provider surveys. Such a strategy would provide not only new data but also
a basis for linkage of data on a population-based sample of individuals with
data on their health care providers, thus further enhancing the benefits.
Since a central feature of the panel's proposed design framework is to
link the NHIS design with the operations of the National Health Care Data
System, it is useful to review some of the design features of the existing
provider surveys to see what degree of integration may already exist. As
shown in Table 1 in Chapter 3, the primary sampling units for the National
Hospital Discharge Survey (NHDS) and the National Ambulatory Medical
Care Survey (NAMCS) are subsamples of the NHIS primary -:~mple. This
design implies that samples of providers for these two survey currently
being chosen exclusively from lists of hospitals and medical practices that
are located in some of the same areas in which NHIS interviewing is being
conducted. This geographic integration, in tum, must also imply that some
degree of operational coordination already exists, or should exist, among
these surveys. Moreover, data collection in all these surveys is being con-
ducted by the Bureau of the Census. Extension of this level of design
integration to nursing homes is currently being planned for the next round
of the National Nursing Home Survey (NNHS).
The key elements or components of the proposed framework are to:
(1) Change the origin of the provider samples from listings of provid-
ers and service settings maintained by NClIS to identification of
providers and service settings by respondents to the National Health
Interview Survey (at least for those providers not in the inventories
maintained by NCHS).
(2) Sample from NHIS respondents to gather longitudinal person-based
data on the health status and health care received by individuals
along with the associated costs and expenditures.
(3) Modify the sampling design of the National Nursing Home Survey
to collect longitudinal data on health care utilization by the institu-
tionalized population not presently covered by the NHIS.
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DESIGN FOR A NATIONAL HEALTH CARE DATA SYSTEM
67
(4) Sample from NHIS respondents and collect longitudinal data on the
process of health care, the utilization of providers, and the costs
and expenditures associated with episodes of illness.
NHIS-Based Sampling of Providers
As discussed in Chapter 3, one of the features of the NCHS plan is to
extend the types of providers to include alternative sites of health care
covering hospital and surgical care, ambulatory care, and long-ter~ care.
The panel is concerned that current NCHS plans for expanding the coverage
of the National Health Care Survey are not as broadly based as they should
be with respect to national statistics on providers of health care. The panel
therefore proposes a method for extending the coverage of providers of
health care that is capable of covering the full range of providers, both
physicians and nonphysicians.
Although well-developed lists of short-term hospitals, office-based physi-
cians, and nursing homes do currently exist, a major problem with the pro-
posed extension of health care providers is the lack of adequate lists from
which these "other providers" can be sampled and the high cost of developing
and maintaining up-to-date inventories for each category of health facility or
provider in a set of first-stage sampling units. This section outlines the pan-
el's proposal for a sample design that will meet in a cost-effective manner the
need established by NCHS to expand its data gathering to be able to include a
fuller range of providers and health care settings than currently planned.
Rather than develop separate sampling frames for each and every type
of "other provider" (i.e., other than short-stay hospitals, office-based physi-
cians, and nursing homes), the panel proposes that appropriate national
samples of "other provider" categories be identified by screening National
Health Interview Survey respondents for the names and addresses of the
health care providers and settings they visited in a very recent period, such
as a defined two-week reference period.
The essence of the proposed design is the identification by NHIS re-
spondents of providers to be sampled for the expanded National Health
Care Data System. The design is flexible, in that it can be applied for any
type of provider, and it can be readily applied to collect data for new health
care settings that emerge over the course of time. Each sampled provider is
subsequently contacted and asked to provide data for the visit that led to
the provider's selection and for a sample of other visits. Apart from the
manner in which the providers are sampled, the survey procedures can be
similar to those used in the current provider surveys. The basic sample
design and data-gathering plan for the NHIS does not change, except that
the questionnaire would have to be expanded to collect information to
identify and locate providers that the respondents visited in the specified
reference period.
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TOWARD A NATIONAL HEALTH CARE SURVEY
The primary advantage of changing the origin of a sample of "other
providers" from provider lists to reports of health provider care received by
NHIS respondents is the significant savings in both cost and time to acquire
sampling frames for each type of "other provider." The time factor is of
considerable concern, particularly in a changing environment, with newly
emerging modes and numbers of health care providers. The NHIS-based
approach offers rapid identification of emerging health care providers, which
is just not possible with the current approach of developing and maintaining
inventories for given types of providers to serve as sampling frames.
Another important and attractive feature of this sample design is that
the health providers in the NHIS-based sample are selected with probabili-
ties directly proportional to their use or size (i.e., number of visits for health
care they receive in a given period), provided that (a) the NHIS interviews
are spread evenly throughout the time period and (b) the NHIS respondents
are sampled with equal probability. In practice, the latter condition is not
satisfied because, for instance, of the oversampling of minority populations.
However, a subsample of NHIS respondents can be drawn in a manner that
creates an equal probability sample of NHIS respondents for use in sam-
pling providers.
The selection of providers with probabilities proportional to size (PPS)
enhances the potential for increased reliability of the estimates derived from
the sample of visits subsequently selected to gather utilization data from
each type of provider surveyed. The selection of a constant number of
visits from each selected provider yields an equal probability sample of
visits and balances the data-gathering workload. Thus, for example, 20
visits might be sampled from each selected provider. The choice of the
number of visits to select from each provider depends on cost and variance
considerations. This number may well vary among different types of pro-
viders. Research is needed to determine the most appropriate number of
visits to select from each provider.
The panel recognizes that there are a number of potential difficulties in
the implementation of this design. It relies on complete reporting of visits
by NHIS respondents; significant underreporting of certain types of visits
(such as those for less socially acceptable diseases) could create serious
problems. Also, the NHIS respondents may not be able to provide suffi-
ciently accurate inflation to enable the sampled providers to be located.
Some of the named providers might be located outside the NHIS PSUs,
thereby increasing the cost of subsequent data collection. The sampled
providers may be reluctant to provide the requested visit data. How should
providers sampled in this way be approached to maximize their coopera-
tion? Methodological studies will clearly need to be conducted on such
issues before this design is implemented.
Since, for some types of provider visits, recalling visits could be prob-
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DESIGN FOR A NATIONAL HEALTH CARE DATA SYSTEM
69
lematic, the decision to limit recall to 1-2 weeks may be necessary. The
only recent comparable experience on obtaining permission to contact pro-
viders from household samples comes from the National Medical Expendi-
ture Survey (NMES), wherein signed respondent permission and successful
contact were achieved for 81 percent of identified providers. Based on
preliminary estimates, approximately 40 percent of the nonresponding pro-
viders in this process were lost because of an inability of the interviewer to
obtain sufficient identifying information for the provider (Harper et al.,
1991~. The remainder were lost because of the interviewer's inability to
obtain signed permission or because the provider refused to comply with
the request for records data. There is also the issue of people making
multiple visits to providers for different conditions and the problem of matching
respondent reports to provider records. Further research would be needed
to investigate the level of recall error and to minimize this attrition. Experi-
ence would suggest that keeping attrition at an acceptable level is at least
possible, given the relatively high household survey response rates achieved
by the NHIS.
Identifying a provider sample through a household sample chosen with-
in well-defined primary sampling units presents the logistical problem that
some providers will be located outside their boundaries, some perhaps some
distance away. Since excluding providers outside the PSUs would destroy
the validity of the provider sample, there is no recourse but to attempt to
enroll them all. This then raises the issue of what percentage of sample
providers will be located outside the boundaries and how best one might
handle dealing with them. Recent experience from NMES suggests that this
would be a relatively minor problem for the hospitalization and the ambula-
tory care components. Research would be needed, however, to find creative
yet practical ways to administer these surveys for providers outside the
PSU, for whom field staff might have to commute some distance.
Recommendation 4-1: The panel recommends that providers
other than those currently covered i.e., short-term hospitals,
office-based physicians, and nursing homes- be surveyed using
provider samples generated from the list of providers visited by
respondents to the National Health Interview Survey as identi-
fied through the survey screening.
The proposed NHIS-based sample design for providers is particularly
useful for providers for whom no list frames exist, and especially for newly
emerging health care settings. In principle, the design could be expanded to
include visits reported by NHIS respondents to short-stay hospitals and
office-based physicians. Currently, since provider utilization in terms of
number of visits is not known in general, the NHDS uses proxy measures of
size (e.g., the number of beds) to select samples. The NAMCS is not a PPS
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TOWARD A NATIONAL HEALTH CARE SURVEY
sample, whereas the NHIS-based sample is. Thus the NHIS respondent-
generated samples of short-stay hospitals and office-based physicians con-
ceivably could be more efficient statistically. By contrast, hospitalizations
(or other visits) that lead to deaths or institutionalizations will not be repre-
sented in the NHIS-based sample, with resulting biased estimation.
Clearly, many factors can enter into a decision whether or not to change
the origin of the samples of short-stay hospitals and office-based physicians
from inventories currently maintained by NCHS to identification of such
providers by NHIS respondents. As there is insufficient information on the
relative feasibility, costs, and efficiency of these alternative approaches,
NCHS should research the issues prior to any final decision.
Recommendation 4-2: The panel recommends that NCHS ex-
am~ne the feasibility and utility of selecting its samples of short-
term hospitals and office-based physicians from inventories of
each of these types of providers visited by respondents to the
National Health Interview Survey and identified through the
survey screening.
NHIS-Based Surveying of Cohorts of Individuals
As discussed in Chapter 2, comprehensive data on the use of health care
services are urgently needed on a continuous basis if the critical issues of
cost, access, and quality of care are to be meaningfully addressed. This
implies continuously gathering longitudinal, person-level data reflecting patterns
of care sought and received, including what services were provided, by
whom, and with what outcome, as well as the associated charges by type of
service and how the charges were paid.
The panel believes that the National Health Care Data System can and
should meet these data needs. Specifically, the panel proposes a prospec-
tive design in which the NHIS will be used to identify cohorts of individu-
als to be interviewed periodically over specified time periods to provide
longitudinal data on their health care utilization and expenditures.2 The
national health care statistics on key policy-related items generated by these
cohort surveys should be published annually.
The cohorts based on subsamples of NHIS respondents should be se-
lected so as to permit provision of national statistics that would best address
health care policy issues. In addition, oversampling should be used to
sample policy-relevant cohorts such as low-income people, uninsured peo-
ple, minorities, people with poor perceived health status, disabled people,
2 The analysis of longitudinal data is an active area of research with many new techniques.
For an introduction of this literature see Kasprzyk et al. (1989); Cox and Cohen (1985);
Duncan and Kalton (1987); Heckman and Singer (1985); Kalton et al. (1989); Kasprzyk and
Jacobs (1991); Office of Management and Budget (1986); Pearson (1989); Ruggles (1991).
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DESIGN FOR A NATIONAL HEALTH CARE DATA SYSTEM
71
and elderly people. Since unbiased national estimates for the general popu-
lation should be generated in any event, sample cohorts representing those
individuals not eligible for any of the special interest cohorts should also be
selected from among the NHIS respondents and interviewed periodically as
well.
To ensure the completeness and accuracy of the information reported in
the follow-up interviews by sample persons on the health care services they
received, the cost of those services, and the sources of payment, the provid-
ers of those services and the health insurers will need to be contacted to
obtain the details of each provider visit experienced by at least a subsample
of the persons in the cohort. Signed permission to make these contacts and
to release the relevant data will need to be obtained from each person
sampled. The relative feasibility of collecting such signed permission forms
by mail versus face-to-face, for those interviewed by telephone, will need to
be explored by NCHS.
Numerous design issues will need to be addressed, for example: (1)
timing in the selection of the samples of NHIS respondents relative to the
initiation of data collection, (2) frequency of the periodic follow-up inter-
views, (3) mode of the initial follow-up and repeat interviews, and (4)
respondent motivation and sample attrition.
One problem that arises in selecting the samples for follow-up from
NHIS respondents is the potential for a sizable time interval between the
NHIS interviews and the initiation of the follow-up interviews and the at-
tendant loss of sampled individuals who have moved in the interval. To
minimize recall errors, the follow-up interviews should be conducted fre-
quently, say once a quarter, or even more frequently if suggested by the
findings of the 1987 NMES, conducted by the Agency for Health Care
Policy and Research. The cost of carrying out the follow-up interviews
could be mitigated by the use of computer-assisted telephone interviews
whenever possible. Retention of sampled individuals for the full set of
follow-up interviews is always a challenge; appropriate incentives to mini-
mize attrition should be devised.
The selection of a sample of individuals from NHIS respondents to
collect data on health care use and expenditures is not a new concept. An
NCHS-funded study (Cox et al., 1987) evaluated alternative designs for
linking the 1987 NMES with the NHIS. Included in the alternatives exam-
ined were optimally allocated designs that utilized data collected in the
NHIS with respect to race, poverty status, age, and health status to construct
strata. The study found, for example, that the NHIS-linked, optimally allo-
cated, not-self-weighting designs for these policy-relevant strata, at least,
could achieve significant cost savings for estimates of average annual utili-
zation and expenditures by type of provider relative to the cost of achieving
the precision of an unlinked design. The optimally allocated design essen-
tially uses characteristics of NHIS respondents to oversample potentially
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TOWARD A NATIONAL HEALTH CARE SURVEY
heavy users of health care services, thereby yielding greater efficiency.
This design, however, was not in the final plan for the NMES that was
developed.
The panel recognizes that surveys for gathering information on medical
expenditures are expensive. Yet it believes that it is important in today's
environment to be informed on a current basis about health care needs,
patterns of care received, and the associated costs. Linking the cohort
samples to the NHIS and oversampling these samples in policy-relevant
domains, together with greater use of telephone interviewing, might pro-
duce the needed data at somewhat less cost than has been experienced to
date in previous population-based medical expenditure surveys.
It should be noted that the proposed design for a continuing longitudi-
nal survey of health care utilization and expenditures is in many ways simi-
lar to that for the NMES. When fully operational this survey would gather
basic data similar to the data gathered in NMES, but at a somewhat lower
cost. The proposed design will use a cohort of individuals selected from the
NHIS respondents, and the screening to identify providers will be done
within the context of NHIS, an ongoing survey with an existing cadre of
interviewers. Basic data on health care costs and expenditures (both out-of-
pocket and total expenditures) will therefore be available on a more current
and resource-efficient basis than is possible now from ad hoc comprehen-
sive surveys conducted at infrequent intervals.
Recommendation 4-3: The panel recommends that NCHS de-
velop and implement, as a component of the National Health
Care Data System, a continuous, longitudinal survey of health
care utilization and expenditures and their health care provid-
ers, using cohorts of individuals selected from among National
Health Interview Survey respondents.
The panel believes that it is essential that NCHS work in coordination
with the Agency for Health Care Policy and Research in implementing this
recommendation, which it sees as a natural next step in the development of
routine collection of health care cost data.
NNHS-Based Surveying of Cohorts of Residents
Currently little or no data are available for residents of nursing homes
on their use and expenditures for health care services from other providers
(i.e., other than the nursing home) while institutionalized. This deficiency
can be addressed by collecting health care utilization and expenditures data
for a sample of nursing home residents on a continuous basis in a manner
comparable tO that outlined in the proposed NHIS-based cohort survey.
Thus a sample of current residents in each NWHS sample facility could be
selected periodically, to serve as a cohort of institutionalized persons. Longitudinal
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DESIGN FOR A NATIONAL HEALTH CARE DATA SYSTEM
73
data, analogous to that collected from the NHIS-based cohorts, on the use
of other health providers by members of the cohort could then be collected
periodically, over the course of a year, from nursing home records and from
the health care providers who treated them. The field work for such a
design is facilitated by the center's plan to conduct the next NNHS in the
subsample of the NHIS PSUs.
The panel urges NCHS to explore the use of this method to collect
health care use and expenditure data for people in other types of long-term
health care institutions as well, such as mental hospitals.
Recommendation 4-4: The panel recommends that NCHS de-
velop and implement a survey capability to obtain longitudinal
data for cohorts of residents of nursing homes, while institu-
tionalized, on their use of and expenditures for health care re-
ceived from providers other than the nursing home itself. NCHS
should explore the possibility of obtaining this information for
residents of other long-term institutions.
There are other subgroups of the population, such as the homeless,
migrant workers, people in jails and prisons, who are not well captured by
the current NHIS sampling design, even when it is supplemented by nursing
homes and possibly federal and long-ten hospitals. The implications of
excluding these groups in surveys monitoring the nations's health status and
the use and costs of health services are obvious, considering that these
groups are at high risk of poor health. The panel regards the appropriate
representation of these subgroups, while difficult, to be very important and
urges NCHS to initiate research to find ways to adequately capture these
groups in their surveys.
NHIS-NN~S-Based Surveying of Episodes of Illness
An important feature of the proposed National Health Care Data Sys-
tem is the capability of collecting longitudinal data on the health status and
health care utilization of a population-based sample of individuals and link-
ing them with the associated information on the health care providers. The
design strategy recommended in the previous sections represents a major
step forward by linking information on the individuals with visits to health
care providers, thus enabling important policy-related data on the condition
of the health care system to be collected and reported continuously. How-
ever, the design does not necessarily capture the complete dynamics of the
illness and treatment process. In order to more fully portray the health care
system, data are needed that reflect the illness and treatment process from
onset of the illness, diagnosis, treatment, and outcome.
Although there are a number of potential ways in which such longitudi-
nal data on individuals can be organized (for instance, by period of observa-
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TOWARD A NATIONAL HEALTH CARE SURVEY
lion), an attractive organizational concept from many standpoints is the
"episode of illness" and the patterns of care associated with such episodes.
The episode model focuses on the observed patterns of care as a reflection
of the care sought and received in conjunction with an episode of illness
through possible treatment and outcome. Thus an alternative approach to
gathering population-based statistics on health care services, wherein one
follows a cohort of individuals, could be to limit the longitudinal data col-
lection to those persons reporting art illness episode. This model could be
used for studying patterns of utilization, cost of care, quality and access to
care, and the role of the different types of providers and technologies. Since
only those persons experiencing an episode of illness would be followed,
this approach also has the potential to gather the requisite health care data
more efficiently than from a cohort representing all persons, as presented
earlier, and could conceivably replace it in the long run.
The panel recognizes that despite the attractiveness of the concept and
its many advantages, its application has been relatively limited because of
practical difficulties. Steinwachs (1991) identifies several problem areas
that have limited the use of the episode of illness concept in examining
health services utilization. These include the lack of standard definitions
and classifications to be used in constructing the episode of care resulting
from an episode of illness, as well as the lack of standard summary mea-
sures of episode characteristics, such as duration of an episode, intensity of
care, level of use, cost, and outcomes.3 The application of the episode
concept to chronic conditions is not clear: Is there a single long episode, or
is it more properly conceptualized as a series of episodes for maintenance,
care, or treatment of acute exacerbations?
These issues should be resolvable, both from methodological and re-
source perspectives. In particular, classifications will need to be developed
to resolve such issues as: When does an episode begin (e.g., does it require
limitation in activity for at least one day)? When does an episode of illness
end (e.g., is this the last day of any limitation)? When does the care for the
illness end, how should comorbidities be identified and included in the
episode, when is the episode part of a chronic disease process and when is
an acute and time limited condition, and when should outcomes be mea-
sur-d (e.g., single or multiple points in time)? Clearly, an investment in
methodological work is needed by NCHS and the Agency for Health Care
Policy and Research to resolve these and other issues before pursuing the
theoretical attractiveness of the episode concept into application, particular-
ly in large-scale surveys.
3Recent literature examining definitional and operational issues associated with episode of
care analysis includes, among others, Keeler (1991, 1988a, 1988b), Hornbrook (1985), Star-
field et al. (1991), Frank et al. ( 1991), and Prien et al. (1991).
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Assuming that the definitional and related issues are resolved, the panel
proposes a design that would efficiently use survey resources to develop
episode information. Within the context of a population survey, those indi-
viduals reporting a recent onset of an episode of illness (within two weeks)
would be the target population, including mental and emotional illnesses.
This group can be expected to include many minor self-limited illnesses or
injuries for which no care is sought, yet there may be some individuals who
are at the early stage of a serious condition and have not received care or
made an appointment for care. It would be important to follow all individ-
uals seeking care, plus those who have not sought care, to the end of the
episode of illness or to the end of the care process, which ever comes later.
This would provide unique information on patient outcomes, their relation-
ship to care seeking and to the pattern of care received from one or more
providers. The interpretation of the interview and follow-up data can be
substantially enhanced by supplementing these data with information from
providers and patient records for those episodes receiving care.
The population can be viewed as consisting of people with different
patterns of illness. For example, experience would range from no episodes
during the specified reference period through minor episodes of relatively
short duration, that require no provider care, to acute episodes that would
require provider care and end in either death or recovery. Some individuals
may experience more than one illness episode (possibly overlapping) during
the period. The majority of persons with short-duration episodes would be
part of the noninstitutionalized portion of the population. More episodes
associated with chronic conditions (i.e., those extending over longer peri-
ods of time) than short-term acute episodes are often experienced by per-
sons institutionalized in long-term health care facilities.
A sample of eligible individuals with selected episodes would be fol-
lowed until the outcome of the episode occurs, or until some operationally
defined stopping point is reached (e.g., six months after onset, some defined
state of health or disability). Defining a stopping point for episodes such as
injuries with a permanent disability is complicated, even if an arbitrary time
period after onset is used. A full range of data (e.g., diagnosis, provider
visits, costs and treatment strategies tied to individual provider visits, limi-
tation of activities, and final outcome) would be gathered for each selected
episode from health care providers and insurers.
Identifying information about each reported provider, along with signed
permission to abstract data from the medical and accounting records for the
respondent at each identified provider, would be obtained at the conclusion
of each initial and each follow-up interview. Permission forms for the
providers visited at the time of the first interview may not be sufficient,
since persons may go to other providers after that time. The length of the
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TOWARD A NATIONAL HEALTH CARE SURVEY
reference period must reflect the respondent's ability to recall visits and
minor episodes.
The episode of illness model illustrated here is linked to the NfIIS
design and operation. Except for expansion to the NfIIS questionnaire to
accommodate screening for illness episodes in addition to obtaining identi-
fying information for visited providers from the list of providers, the exist-
ing design and data gathering plan for the NHIS would not change. The
process of screening is similar to that described for the other cam; --ants of
the design framework described in the preceding sections and wary ~ pro-
ceed in the manner described below.
The NHIS respondents first would be screened to determine those who
began an episode of illness during a short reference period immediately
prior to the interview. Thus, a representative sample of the group of illness
episodes occurring to individuals over a time period of interest would be
defined, then repeat contacts would be made tO chart the course of the
episode arid to determine when it was completed. Contacts would be made
with the providers of care for the episode to collect data on the treatment
process, outcome, and costs.
A subsample of the NtIIS respondents would be screened for all pro-
viders visited and illness episodes suffered during a recent reference period.
Two types of illness episodes can be identified through this screening pro-
cess: (1) those with one or more provider visits (other than to NNHS-
eligible nursing homes) occurring during some reference period ending jUSt
prior to the regular NHIS interview and (2) those that ended during the
same reference period but for which no provider visits occurred during the
course of the episode (e.g., colds, flu, minor injury, and illness for which
one cannot afford to seek care). Only those persons experiencing a "new"
illness episode that led to utilization of medical care would be eligible for
follow-up. In other words, the subset of illness episodes, with a provider
visit occurring during the reference period, becomes the sampling frame of
illness episodes screened for further follow-up beyond the NHIS screening
interview. By restricting the sample to episodes that begin in the two-week
period immediately prior to interview, the sampling probabilities for the
group of episodes are easily determined and the complication of selecting
episodes with probabilities proportional to their length is avoided.
A major limitation of this model as illustrated is that the emphasis on
new episodes does not adequately address the need for information on chronic
illness care, both routine maintenance and acute problems. An option for
capturing information on the treatment of chronic conditions is to determine
if during the past two weeks the individual experienced limitations in activ-
ity related to a chronic condition. If yes, information could be sought
regarding whether the limitation was more severe, the same, or less severe
than previously. If the limitation is worse, this would define a "new"
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DESIGN FOR A NATIONAL HEALTH CARE DATA SYSTEM
77
episode in the ongoing care of the chronic condition. These would be
followed using a methodology parallel to episodes for conditions that are
not identified as chronic.
It is also likely that a significant number of people experiencing a
chronic condition will never experience a well-defined "chronic episode,"
with a well-defined beginning and end, yet will interact with health care
providers periodically. If that is the case, use of the episode of illness
approach would be limited to episodes of acute illness. Under such circum-
stances, a sample of NHIS respondents with chronic conditions would need
to be identified and interviewed periodically to determine their utilization
and expenditures for health care during a time period of interest, such as a
calendar year.
Since residents of nursing homes (or other long-term care institutions)
are not included in the NHIS, selection of a subsample of current residents
of the NNHS sample facilities should be considered for tracking episodes of
illness that require health care services to be sought outside the nursing
home. To facilitate episode screening, the NNHS sample would be subsam-
pled, similar to the NHIS household sample. To properly reflect seasonal
variations in illnesses, the NNHS subsample should be evenly spread over
time.
The episode screening of sampled nursing home residents would be
carried out in similar fashion to the screening of the NHIS respondent sub-
sample. The purpose of the screening is to identify any episode that led to
medical care during the reference period, not including the episode that
caused the sampled individual to become a patient in the nursing home.
The information to be collected for residents suffering an episode of illness
should be essentially the same as that collected about episodes of illness
occurring to the NHIS respondent subsample.
Recommendation 4-5: The panel recommends that NCHS un-
dertake research in collaboration with the Agency for Health
Care Policy and Research to examine the methodological issues
of definitions and classifications and to determine the feasibility
of using the National Health Interview Survey and the National
Nursing Home Survey to generate a sample of episodes of ill-
ness; the sample should be followed longitudinally to collect
data on the associated medical care use for the episode from
both the sample of individuals and the health care providers.
Effectiveness and Efficiency
In the face of rapidly rising health care costs, there is growing interest
in treatment effectiveness in relation to cost. The episode of illness model
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TOWARD A NATIONAL HEALTH CARE SURVEY
offers an opportunity to collect not only data on each component of health
care received and their costs, but also data on the outcomes of that care.
Broadly based national statistics bearing on the overall effectiveness and
efficiency of the U.S. health care system would thus become possible.
The validity and cost of gathering health care data from health care
consumers suggest that every effort should be made to take advantage of
administrative records, such as health insurance claims files from both pri-
vate and public insurers, patient medical records, and patient billing records.
Medicare claims files provide a unique opportunity to study health care
services received and costs for Medicare recipients. A similar set of claims
files is needed for a national sample of persons younger than age 65.
Recommendation 4-6: The panel recommends that NCHS con-
duct research and develop procedures for data systems that
enable linkage of health care outcomes to health care received
and health care costs. The panel further urges NCHS to exam-
ine the feasibility of collecting health insurance claims files from
both private and public insurers for individuals included in the
samples selected from the National Health Interview Survey and
the National Nursing Home Survey to study health care utiliza-
tion and costs.
Relation to the NHIS Redesign
As stated early in the chapter, a central feature of the panel's recom-
mendations is to link the NHIS design to the operations of the National
Health Care Data System. Work is under way on the 1995 redesign of the
NHIS based on the 1990 decennial census, which will affect NHIS data
collection for at least 10 years. The decisions made on the NHIS redesign
will therefore have implications for the successful and timely implementa-
tion of the panel's recommendations for an integrated design framework for
collecting health care data.
Recommendation 4-7: The panel recommends that NCHS take
into serious consideration the recommendations in this report
relating to the National Health Care Data System before reach-
ing final decisions on the 1995 redesign of the National Health
Interview Survey.
POTENTIAL BENEFITS OF THE PROPOSED
DESIGN FRAMEWORK
Adopting the panel's recommended design framework for a National
Health Care Data System has several potential advantages, some of which
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DESIGN FOR A NATIONAL HEALTH CARE DATA SYSTEM
TABLE 2 Summary of Data Produced Under the Design Framework
Linked to Data Collected under
Level NHIS Through Design Frameworka
Person NHIS respondent Disability days
Physician visits
Acutelchronic conditions
Limitations of activities
Hospital stays
Insurance coverage
Special topics
Access to care
Preventive care
79
Episodeb First provider Cost of care
visit during Episode outcome
an episode Pattern of pro rider care
l~cidencelprevalence
Duration
Content of provider care
Seventy of illness
Access to care
Visit Any provider Diagnosis
visit during Length of stay
episode Disposition
Treatment
Cost of care
Provider Any provider visit Facility profile
whether or not for Health promotion practices
an episode Treatment practices
aCulTently unmet needs in italics.
bIncludes only illness episodes leading to the utilization of health care. Minor episodes not
requinug provider visits are also reported by respondents to the National Health Interview
Survey.
are tied to meeting unmet information needs (Table 2~. The data system
when fully implemented would produce substantial new data at the person
and visit level. Some of the new items are simply add-one to questionnaires
for the existing provider surveys; others would be obtained from new sur-
vey activities. The proposed data system in the long run would also provide
a unique population-based database to facilitate assessment of the cost-
effectiveness of treatment programs for specific health conditions.
The panel's proposed data system would be able to meet the need for
direct data linkage between the person and provider data. Information gath-
ered for any treatment event, including data on providers visited or individ-
ual provider visits, can be linked to the person who reported the provider and
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TOWARD A NATIONAL HEALTH CARE SURVEY
the visit. Thus, for example, data on the condition for which the treatment
was provided and its outcome could be related TO the socioeconomic ch~ac-
teristics of the individual. Linkage between person-level and provider-level
data also provides a basis for confimning the illness diagnosis.
The proposed data system would give NCHS sufficient flexibility to be
able to adapt to changing data needs. One important facet of this flexibility
is the ability to shift the focus of sampling as needed. For example, certain
segments of the population (e.g., blacks, Hispanics, the uninsured, the eld-
erly) can be oversampled by altering the NHIS subsampling process. Sam-
ple sizes for specific conditions also could be controlled by altering the size
of the NHIS subsample that is screened or by oversampling provider visits
for rare conditions in the provider surveys.4 The flexibility tied to sampling
needs is limited only by the difficulty that NCHS would have in making the
design alterations and by the time it would take to implement them.
Current NCHS scheduling plans to field the existing provider surveys
annually would not be altered if the panel's recommended design frame-
work is adopted. Finally, the timing is right to make the kinds of changes
required by this design, since in recent years design integration involving
the NHIS has been given a priority within NCHS and since significant
redesign work is currently under way for the two surveys in which the
greatest impact of change would be felt (i.e., the NHIS and the NNHS).
IMPLEMENTATION STRATEGY
The panel recognizes that, despite its many potential benefits, adoption
of the recommended design framework raises several important issues that
would require careful examination and resolution prior to making final de-
cisions on the details of the design.
Many of these issues are related to some of the screening and patient
follow-up procedures. Perhaps the most important are: (1) to identify pro-
vider visits, (2) to obtain useful information to contact identified providers,
(3) to obtain permission from the patients to peruse the provider records of
those whom the NHIS respondents identify, and then (4) to successfully
enroll the providers and the patients in the study.
Another important issue regarding the design of the proposed National
Health Care Data System as recommended by the panel is the capacity to
follow persons in receipt of care for a fixed length of time or until outcome,
and in some instances beyond NHIS PSU boundaries. Follow-up might
conceivably involve some combination of face-to-face and telephone inter-
40ther methods for sampling for rare conditions should also be investigated' including mul-
tiplicity or network sampling. A description of this and related methods and an introduc-
tion to related literature are included in Sudman and Kalton (1986); Kalton and Anderson
(1986); Sudman et al. (1988); Nathan (1976); Sirken (1972).
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DESIGN FOR A NATIONAL HEALTH CARE DATA SYSTEM
81
viewing. Both modes have already been considered for use in the NHIS and
the NMES. The telephone, for example, might be used only as a backup to
the face-to-face follow-up if the person moves away from the area. Addi-
tional research into finding the most effective strategies for episode follow-
up are necessary.
As discussed earlier, although the concept of episodes of illness is at-
tractive and such data would prove to be a very valuable analytical data-
base, especially for medical effectiveness research, experience with its appli-
cation is limited and problematic. Developing the capability to generate data
on episodes of various types of illness raises important and complex method-
ological issues associated with definition, classification, and measurement.
Finally the potential for difficulties with the process of linking large
person-level data files from the persons' visited providers, their health care
utilization, the process of care during an illness episode, and the final out-
come should not be underestimated.
Recommendation 4-8: The panel recommends that NCHS es-
tablish a research agenda to determine the feasibility of its rec-
ommended course of action. If found feasible, the panel recom-
mends that NCHS adopt the proposed design framework (with
adjustments as warranted by the research) for a National Health
Care Data System.
In conclusion, the panel recognizes two different, but not mutually ex-
clusive, courses of action for establishing an integrated National Health
Care Data System. The first course of action, put forth by NCHS, calls for
limited geographic integration of the provider surveys with NlIIS, extend-
ing the coverage of the provider surveys, and adding patient follow-up to
the NHDS and the NAMCS. In effect, this plan envisions a collection of
slightly modified provider surveys with follow-up components as the Na-
tional Health Care Survey.
The panel believes this course falls short of meeting anticipated health
inflation needs for the next century. It therefore proposes a different and
more ambitious course of action, one that encompasses most of the features
of the NCHS proposal, but also calls for a significant long-term expansion
in the breadth and depth of information to be gathered through a compre-
hensive National Health Care Data System.
The section outlines below steps in a multiyear implementation strategy
for the panel's proposed plan starting in 1992. The strategy is divided into
four, at times overlapping, phases involving the initiation of the research
agenda, developing and implementing the panel's design framework and
recommendations for improvements in content and coverage of the informa-
tion gathered, followed later by research into the feasibility of surveying
episodes of illness and the associated patterns of care and outcomes.
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Phase I: 1992-1995
TOWARD A NATIONAL HEALTH CARE SURVEY
Suggested Implementation Schedule
(1) NCHS begins work on the development and implementation of the
panel's proposed design framework and He recommended improvements
in the data content for the data system. Many aspects of the pro-
posal have minimal impact on the designs of the underlying exist-
ing survey vehicles.
(2) NClIS initiates a research program to carefully consider the issues
identified in the preceding sections of the report. NCHS should
work in collaboration with the Agency for Health Care Policy and
Research in researching the issues relating to the feasibility and
efficacy of gathering data on episodes of illness.
(3) NCHS begins the process of convincing the Department of Health
and Human Services, the Office of Management and Budget, and
the Congress of the importance of this effort for federal health care
policy and to ensure that this effort receives adequate funding and
staff resources.
Phase II: 1995
NCHS begins implementation of the panel's recommendations with any
modifications and adjustments as warranted by the research results to
date.
Research agenda continues.
Phase III: 1994-1997
NCHS sets upon a one-year period to flesh out the design protocols for
the panel's plan if found feasible in Phase I and with modifications as
warranted by the results of the research.
NCHS begins developmental work for implementation of the panel's
long-range proposal for surveying illness episodes.
Phase IV: 1997-2000
NCHS commences implementation of all components of the panel's
proposed design framework for a comprehensive National Health Care
Data System.
Representative terms from entire chapter:
nhis respondents
