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c
Glossary and Acronyms
GLOSSARY
Adjusted, adjustment In a statistical analysis, the process of manipulating or
stratifying the values of independent variables so as to minimize their confounding
influence on the relationship or association between an independent variable of
interest and the dependent variable.
Association A correlation or relationship that may or may not be causal, for
example when events occur more frequently together than one would expect by
chance alone.*
Bias "Any systematic error in the design, conduct or analysis of a study that
results in a mistaken estimate of an exposure's effect on the risk of disease"
(Gordis, 1996, p. 183~.
Bivariate analysis A statistical method to characterize the relationship between
an independent variable that measures an exposure or treatment (e.g., a potential
cause) and a dependent variable that measures an outcome or effect.
Causality A relationship that may exist between an exposure or treatment (cause)
and an outcome (effect), depending in part on the strength of the association
between exposure or treatment and outcome.
*Adapted from the Academy for Health Services Research and Health Care Policy glossary at http:
//www.academyhealth.org/publications.glossary.pdf, accessed February 4, 2002.
155
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Chronic disease A disease that has one or more of the following characteristics:
is permanent; leaves residual disability; is caused by nonreversible physiological
damage; requires special training of the patient for rehabilitation; or may be
expected to require a long period of supervision, observation, or care.*
Confidence interval (CI) A numeric range estimated with a specific degree of
confidence or probability to include a value. Conventionally reported confidence
intervals are ranges in which the actual value of the estimated variable can be
expected to fall 95 or 99 percent of the time, corresponding to probabilities that a
difference or significant result is due to chance of 5 percent and 1 percent,
respectively (p <.05; p <.01~. In reporting quantified results throughout this report
(e.g., odds ratios or relative risks), if the confidence interval is not given, point
estimates have at least a 95 percent probability of being statistically significant.
Confidence intervals are given for findings reported with lesser levels of statistical
. · ~
slgmilcance.
Confounder A variable that is associated with an exposure or treatment of
interest and, as a result, influences the relationship between the exposure or
treatment and an outcome. The ability to adjust or analytically control for the
presence of a confounder depends on how well this variable is measured.
Cost sharing Any provision of a health insurance policy that requires the insured
individual to pay some portion of medical expenses. The general term includes
deductibles, copayments, and coinsurance.*
Covariate A variable that is related to or associated with the study variablets) of
interest.
Cross-sectional Describes a research study in which measurements are collected
and comparisons made among populations at one point in time.
Experimental Describes a study design, for example, a randomized clinical trial,
where researchers use a defined study population, randomly assign members of the
population to exposure or treatment and control groups, control the timing of the
exposure or treatment, and influence the timing of measurements.
Hazard ratio, Cox proportional hazard rate A comparative measure of the
strength of a relationship or association between an exposure, intervention, or
*Adapted from the Academy for Health Services Research and Health Care Policy glossary at http:
//www.academyhealth.org/publications.glossary.pdf, accessed February 4, 2002.
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APPENDIX C 157
treatment (e.g., measured in terms of one or more independent variables) and an
outcome (e.g., measured in terms of a dependent variable) over time for a defined
study population divided into exposure and control groups. For example, to
estimate the influence of an exposure on the length of time until death (mortality
over time), the use of a Cox proportional hazard rate or hazard ratio allows for
multivariate analysis ofthe incremental or proportional difference that each unit of
time would be expected to make in increasing or reducing the risk of mortality. In
this example, the mortality hazard ratio, or incidence of mortality estimated at one
moment in time, is defined as the relative risk of mortality for persons in an
exposure group compared with the relative risk of mortality for members of a
control group.
Health-related quality of life (HRQOL) A research construct developed by
the Centers for Disease Control and Prevention to help monitor progress in
achieving national health objectives. It has been used in the Behavioral Risk
Factor Surveillance System surveys since 1993 and, since 2000, in the National
Health and Nutrition Examination Survey. Its core element consists of four ques-
tions that encompass general self-reported health status, the number of unhealthy
days within a recent time period (e.g., the month before the interview) for both
physical and mental dimensions, and restricted activity days.
Incidence A measure of the probability of a disease or an outcome's occurrence,
defined as the number of new cases within a defined time period for a specific
population divided by the total number in the population (Gordis, 1996~.
Longitudinal Describes a research study in which measurements are collected
and comparisons made among populations over time.
Medically indigent Persons who cannot afford needed health care because of
insufficient income and/or lack of adequate health insurance. Indigent care con-
sists of health services provided to the poor or those unable to pay. Since many
indigent patients are not eligible for federal or state programs, the costs that are
covered by Medicaid are generally recorded separately from indigent care costs.*
Multivariable or multivariate analysis A statistical method to characterize the
relationship among at least two independent variables that measure exposures or
treatments (e.g., potential causes) and a dependent variable that measures an out-
come or effect.
*Adapted from the Academy for Health Services Research and Health Care Policy glossary at http:
//www.academyhealth.org/publications.glossary.pdf, accessed February 4, 2002.
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Observational Describes a research study with a nonexperimental design, in
which researchers gather observations or measurements while not intentionally
affecting the conditions of exposure, the treatment of the study population, or the
. .
timing ot measurements.
Odds ratio (OR) A comparative measure of the strength of a relationship or
association between an exposure or treatment and an outcome for two popula-
tions, where the baseline incidence of the outcome in these groups may not be
known. In this report, it is the relative odds of either (1) developing the outcome
for an uninsured group, compared with the odds for an insured group, or (2)
having been uninsured for a group with an outcome, compared with the odds for
a control population. For example, if the odds of receiving a Pap test are 2:1 in a
group of uninsured women (i.e., two of every three women, or 67 percent,
receive the test) and the odds are 4:1 in a group of women with insurance (i.e.,
four of every five women, or 80 percent, receive the test), the odds ratio of
uninsured compared to insured women is 0.5 (2:1/4:1~. The OR is not a good
estimate of the relative risk (the probability of been screened in the uninsured
group divided by the probability of being screened in the insured group) because
screening is not a rare event.
Predictor, independent predictor ~ , 7 ~
variable (e.g., that measures an exposure or treatment) that is shown to be likely to
influence or predict the value of a dependent variable (e.g., an outcome).
in a statistical analysis. an independent
Prevalence A measure of how common a disease or condition is within a
population, defined as the number of cases in the population at a specified time
divided by the number of persons in the population at that same time (Gordis,
1996~.
Quasi-experimental Describes a research study, for example, a natural experi-
ment, whose design combines experimental and nonexperimental aspects. Typi-
cally, researchers cannot control the timing of the intervention or exposure whose
effects are being measured, or the random assignment of a defined group of study
subjects, but they can influence the timing of measurements.
Randomized trial Describes a research study in which the members of a defined
group of subjects are randomly assigned to at least two groups for the purpose of
analysis: a treatment or intervention group and a control group.
Relative risk (RR) A comparative measure of the strength of a relationship or
association between an exposure, intervention, or treatment and an outcome for a
defined study population, where the baseline incidence of the outcome is known.
It is expressed as the ratio of two risks, namely, the rate of a disease or condition
of interest in the treated portion of the population, divided by the rate in an
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APPENDIX C 159
untreated or control portion of the population. A value of one means that the rates
in both portions are the same.*
Selection bias In research studies, a systematic error in analysis that results when
study subjects are not assigned randomly among treatment and control groups.
Statistically significant See definition of Confidence interval.
ACRONYMS
AMI acute myocardial infarction
ASOC Survey of Aging, Status and the Sense of Control
BRFSS Behavioral Risk Factor Surveillance System
CABG coronary artery bypass graft
CBE clinical breast exam
CDC Centers for Disease Control and Prevention
CI confidence interval
CPS Current Population Survey
ED emergency department
EPO erythropoietin
ESRD end-stage renal disease
FFS fee for service
FOBT fecal occult blood test
FPL federal poverty level
HAART highly active antiretroviral therapy
HCSUS HIV Cost and Services Utilization Study
HCUP Healthcare Cost and Utilization Project
HMO health maintenance organization
HRQOL health-related quality of life
ICU intensive care unit
IOM Institute of Medicine
ISS injury severity score
*Adapted from the Academy for Health Services Research and Health Care Policy glossary at http:/
/www.academyhealth.org/publications.glossary.pdf, accessed February 4, 2002.
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LOS length of stay
MEPS Medical Expenditure Panel Survey
NCHS National Center for Health Statistics
NHANES National Health and Nutrition Examination Survey
NHIS National Health Interview Survey
NMES National Medical Expenditure Survey
NNRTI nonnucleoside reverse transcriptase inhibitor
NRMI National Registry of Myocardial Infarction
OR odds ratio
PI protease inhibitor
PTCA percutaneous transluminal coronary angioplasty
RR relative risk
RW}F The Robert Wood Johnson Foundation
SCHIP State Children's Health Insurance Program
SEER Surveillance, Epidemiology, and End Results Program
SES socioeconomic status
SMI severe mental illness
UCSF University of California at San Francisco
USRDS United States Renal Data System
VA Department of Veterans Affairs
Representative terms from entire chapter:
relative risk
