Assessing Medical Technologies (1985) / Chapter Skim
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3. Methods of Technology Assessment
3. Methods of Technology Assessment
Pages 70-175
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From page 70... ...
The various sections of the chapter were drafted primarily by other authors identified at the opening of each sec tion. 70 Most innovations in health care technology rest on some theoretical ideas held by the innovators.
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From page 71... ...
The reader will probably appreciate, for example, that surveillance and data banks point toward assessing effectiveness, and most randomized clinical trials point toward assessing efficacy. Although randomized clinical trials offer the strongest method of assessing the efficacy of a new therapy, it is recognized that it is not possible to have randomized trials for every version of every innovation.
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2. The data base for the technology was insufficient; there was a call for more studies and better research designs, or accuracy was questioned for diagnostic tests.
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RANDOMIZED CLINICAL TRIALS* The randomized clinical trial (RCT)
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First, the study is conducted under a protocol that makes explicit exactly what questions are to be studied, what treatments are to be applied; and how, to what kind of patients, when, and where. It also specifies how assessment of outcomes will ASSESSING MEDICAL TECHNOLOGY be done and how statistical analyses will be conducted.
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From page 75... ...
If a rather subjective diagnostic test W assesses a condition thought to be related to another test V, then W measured after V is not the same as W measured before V; it may be important that the protocol specify the order in which they are to be done. The careful protocol attempts to specify in advance all procedural steps that may materially affect execution of the trial and interpretation of its results.
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From page 76... ...
, show that for a given standard deviation in batch-to-batch random bias, there is a minimum study size number (the number of experimental subjects) beyond which relying on historical controls, no matter how numerous they are, is inferior to dividing the sample into two equal groups, half experimental and half control.
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The sample size of an RCT may have been planned to resolve differences of a stated size, but when it is completed, questions about treatment comparisons in certain subclasses of patients cannot be resolved. This is not a limitation of the RCT per se, for more questions always can be asked of a body of data than can be answered by it, but one should be warned to think at the planning stage about choosing sample sizes large enough to support adequate treatment comparisons in particularly salient subgroups.
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In addition, the report should specify whether study staff were blind to treatment allocation at key steps like enrollment in study, determination of eligibility, interpretation of diagnostic tests, measurement of outcome, etc. These issues were prominent among those that DerSimonian et al.
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In addition to showing the data, or generously detailed summaries of them, the statistical analysis should state each of the principal questions that motivated the study and what light the data shed on those questions. (Note that this is not the same thing at all as reporting just those results that are statistically significant.)
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Diagnostic technology provides the physician with diagnostic information. However, all diagnostic tests and procedures have associated costs and risks.
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. TN=True negatives FP= False positives EN = False negatives TP = True positives an, , of ILL ()
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True positives + False positives The fraction of patients with a negative test result who are actually free of the disease is called the predictive value negative and is determined by the ratio of True negatives True negatives + False negatives TABLE 3-3 Operating Characteristics of Diagnostic Tests Measure of Performance Characteristic True positives Sensitivity True positives + False negatives Specificity = Predictive values positive = Predictive values negative = True negatives True negatives + False positives True positives True positives + False positives True negatives True negatives + False negatives
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From page 83... ...
_ .~ 8 ~ .7 _ o .6 LO .5 ~ .4 oh o IIJ .3 .1 83 increases, while the proportion of patients with a negative test result who are not suffering from the disease falls. This fact has enormous implications for diagnostic tests, particularly when they are used in populations with a low prevalence of disease, such as when a test is used to screen for the presence of an uncommon disease.
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From page 84... ...
1.0 .8 ASSESSING MEDICAL TECHNOLOGY So, an important use of the ROC curve is to compare alternative tests; an ROC curve that lies above and to the left of another corresponds to the better of the two tests. Then, the choice of a particular k value for that test amounts to choosing the sensitivity and specificity that will be employed.
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From page 85... ...
Few investigators evaluating diagnostic tests identify such patients in their published evaluations. Usually these patients are deleted from evaluations of test performance because they do not fit neatly into a two-bytwo table or ROC.
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do not necessarily imply clinically important differences. Many diagnostic tests require some degree of interpretation to arrive at a test result.
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The problem of technological creep and how to identify optimal times to assess diagnostic technologies is important, unsolved, and vexing. Strengthening the Method Assessments of a diagnostic technology typically are confined to evaluation of the diagnostic performance of the test and do not often measure clinically important impacts of diagnostic tests, such as the therapy chosen or the clinical outcome following therapy.
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How does one evaluate a diagASSESSING MEDICAL TECHNOLOGY noetic test when there is no adequate reference standard? How do patients and physicians value positive test results when there is no effective treatment for the disease of interest?
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From page 89... ...
METHODS OF TECHNOLOGY ASSESSMENT ment and planning systems in place. Substantial progress in the measurement of test performance and more appropriate utilization of tests and procedures requires more comprehensive technology evaluation that focuses on the clinical impact of the technology on the patient and the patient's health.
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This 15 percent of articles was approximately equaled by 16 percent (53 papers) which reported clinical trials.
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METHODS OF TECHNOLOGY ASSESSMENT in hospitals show perinatal mortality of 5.4/1,000 in the home births and 27.8/ 1,000 in the hospital births (Health and Social Service Journal, 1980~. What use can be made of these numbers?
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92 ASSESSING MEDICAL TECHNOLOGY report these. Even if the needed supple- times voiced about the usefulness of mentary information is reported, correct voluntary disease registries.
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Withdrawals may be illdocumented or entirely tacit, with possibly a great effect on the results. The reader may be left to wonder whether the results reported were searched out from among many possible endpoints and thus less likely to be reproducible than significance tests indicate.
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ASSESSING MEDICAL TECHNOLOGY What about penicillin for syphilis, sulfa against pneumococcus, and other examples? These have been called "slam-bang" effects.
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METHODS OF TECHNOLOGY ASSESSMENT other lies the sequence of series-based studies that defy interpretation. The Office of Health Research Statistics and Technology, in its assessment report concerning transsexual surgery (1981)
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gives examples of clinical trials in which, because treatments were modified part way through a trial, a second control group was initiated. Analysis then showed that the two successive control groups in the same setting, meeting the same criteria, differed importantly in their survival experience.
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The contribution of case studies may be enhanced when they incorporate the findings of other forms of evaluation (controlled clinical trials, epidemiologic surveys, simulation studies, costeffectiveness analysis, etc.) and when they are prepared as part of a series of related case studies.
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This information may be derived in part from clinical trials, epidemiologic studies, and other forms of evaluation as well as from data banks, insurance records, vital statistics, and other sources of LEGAL TEACHING MEDICAL MEDICAL SOCIOLOGIC OTHER CASES CASES TECHNOLOGY CASE HISTORIES CASE HISTORIES ~ 1 1 CAUSES CONSEQUENCES Explain the basis for decisions about medical technology (Decisions as the end-point of the analysis) Explain what happens (or will happen)
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Both case studies aimed at causes and case studies aimed at consequences draw upon eclectic sources of information. These range across personal interviews, historical documents, news accounts, company and institutional records, data banks, epidemiologic studies, clinical trials, and more.
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However, oversights and analytic errors in a case study may be more difficult to detect than similar problems in other forms of evaluation, such as reports of a clinical trial. A central problem in the use of case studASSESSING MEDICAL TECHNOLOGY ies for technology assessment is the derivation of generalities from particular instances.
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101 (ease studies of the causes and consequences of decisions about medical technology can be useful forms of technology assessment. Case studies provide the most practical means of investigating some complex and exceptional medical technologies.
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Data bases generally have a hierarchical structure, and they contain and can generate multiASSESSING MEDICAL TECHNOLOGY ple files. Many registers and most data bases are stored in computers, and data bases are maintained and used with the help of a data base management system.
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Some other clinical data bases are those of the Seattle Heart Watch (Bruce, 1974, 1981) , the Coronary Artery Surgery Study (Principal investigators of CASS and their associates, 1981; Chaitman, 1981)
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The National Implant Registry, a private organization, contracts with hospitals to track patients with mechanical and prosthetic implants, such as heart valves and vascular grafts, to preserve accountability between the manufacturer of a device and its recipient and to alert hospitals and physicians to defects and deficiencies. The National Implant Registry has a research component that permits plain language inquiries of its computer records for ASSESSING MEDICAL TECHNOLOGY such things as the frequency and location of use of a specific brand, model, or generic class of a device.
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which the Food and Drug Administration (FDA) and the National Center for Health Services Research (NCHSR)
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and the ASSESSING MEDICAL TECHNOLOGY patient data program (Laszlo et al., 1976) Such an approach has been successfully employed in many cancer centers.
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A system which has such encumbrances cannot be monitored for its quality, cannot be operated by clerks, and cannot be justified in terms of its cost. The process of organizing cancer registries as part of hospital cancer programs does serve a cohesive function that is important but difficult to quantitate.
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From page 108... ...
There should be an executive committee that set policy for the use of data, as ASSESSING MEDICAL TECHNOLOGY has been described for the CCPDS (Feigl et al., 1981~. In the case of federally sponsored programs, particularly those funded by contract, special (although simple)
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From page 109... ...
are useful for evaluating medical technologies in clinical use. Surveys can estimate disease incidence and prevalence rates; quantify the use of medical care services and procedures; and estimate costs and benefits of drugs, procedures, and other technologies.
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used data from the National Health Interview Survey (NHIS) conducted by the National Center for Health Statistics to develop national estimates of visits to physicians' offices and then combined these results with data from the National Ambulatory Medical Care Survey (NAMCS)
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. The National Ambulatory Medical Care Survey, a survey of physicians in private office-based practice, began in 1973.
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These data, in conjunction with demographic and socioeconomic information from the mother's questionnaire, her health habits during pregnancy, and information on many aspects of pre- and postnatal care make this survey uniquely valuable for study of the ways that health care technology is used ASSESSING MEDICAL TECHNOLOGY and how it affects the outcome of pregnancy and delivery. Data from the survey show that in 1980 about 13 percent of mothers received an x ray during pregnancy; nearly one-third of all pregnant women received at least one ultrasound examination; 29 percent of mothers 35 years of age and over received amniocentesis; and almost one-half of mothers in the survey received fetal monitoring (NCHS, 1983f)
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This suggestion seems especially pertinent to longitudinal surveys (Boruch, 1985~. Health Care Financing Administration Data Through its administration of the Medicare and Medicaid programs, the Health Care Financing Administration routinely receives data on such items as its beneficiary population, providers certified to deliver care to the beneficiaries, the use of services, and reimbursements to providers.
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From page 114... ...
Nonresponses can usually be handled more effectively, the data can be processed more quickly, and the quality of responses can almost always be improved because of the greater opportunity for individual handling of problems in smaller data sets. These advantages are not always realized, however; and each reASSESSING MEDICAL TECHNOLOGY ported survey must be studied in detail by prospective users to determine whether the data really will serve their needs.
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From page 115... ...
Standardization of data elements across programs would facilitate cross-survey comparisons. The National Committee on Vital and Health Statistics sponsored the development of three minimum data sets dealing with hospital discharges, ambulatory medical care, and long-term health care (NCHS, 1980c,f; 1981c)
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ASSESSING MEDICAL TECHNOLOGY take in the entire range of observational studies of such things as rates of disease incidence or mortality, causes and risk factors for specific conditions, characteristics of screening and diagnostic tools (including sensitivity and specificity) , the efficacy of preventive measures, follow-up, and outcome.
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METHODS OF TECHNOLOGY ASSESSMENT put variables, somewhat loosely defined, are those observed prior to some effect, event, or use of a technology to be studied and might be more roughly labeled causes and correlates of causes. Output variables are those observed after the use of a technology or other intervention or event and include at least all those features that are effects.
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, not the relevant input ASSESSING MEDICAL TECHNOLOGY variable (DES exposure)
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g., cost-effective analysis/costbenefit analysis)
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ASSESSING MEDICAL TECHNOLOGY would be difficult to approach such issues in this manner (see below)
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For example, if a drug therapy causes blurred vision in 1 person per 1,000 persons treated, a clinical trial including 200 treated patients has only a .18 probability of observing one or more such events. Increasing the sample to 2,000 raises this probability to .86 and a sample of S,000 to .993.
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From page 122... ...
More generally, methods other than clinical trials are used to detect many kinds of adverse outcomes (Bell and Smith, 1982~. Surveillance, even in the crude form of national incidence figures, can offer insight into changes in the epidemiology of a disease, including changes caused by effective disease control measures and programs.
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Some new and existing technologies might be usefully evaluated in a surveillance system. Although maternal serum alpha-fetoprotein appears to be a valuable screening test for neural tube defects, its performance in the field could be better assessed by developing a surveillance system in which laboratory accuracy and standards (including false positives and false negatives)
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Strengthening Uses of Surveillance Various ways to improve postmarketing surveillance have been suggested (IMS America Ltd., 1978~. For example, the ASSESSING MEDICAL TECHNOLOGY Joint Commission on Prescription Drug Use recommended that comprehensive postmarketing drug surveillance be developed for the United States to detect serious adverse events that occur more often than 1 in 1,000 patients and that methods be developed to detect rarer adverse events and delayed events as well as to evaluate benefits.
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METHODS OF TECHNOLOGY ASSESSMENT QUANTITATIVE SYNTHESIS METHODS META-ANALYSIS* Meta-analysis is a statistical method for obtaining quantitative answers to specific questions from collections of primary articles dealing with the same subject.
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They suggest that ASSESSING MEDICAL TECHNOLOGY when a reviewer excludes studies because of methodological deficiencies, valuable information may be wasted based on an assertion (of deficiency) which is not tested.
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METHODS OF TECHNOLOGY ASSESSMENT correlation between treatment and effect is zero (or if significance levels are used, half would be expected to be larger than 0.50 and half smaller than 0.50~. Statistical tests are used to determine whether the observed frequency of findings is significantly different from the 50/50 split of positive and negative correlations expected if the null hypothesis were true.
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This pooling has the effect of increasing overall sample size so that statistically significant differences between the pooled treatment and control groups are observed, where such differences had been observed in only a minority of the nonpooled groups. Example of Synthesis A synthesis was performed on 26 randomized control trials, published between 1965 and 198O, comparing the effects of antibiotic prophylaxis and no-treatment controls on postopASSESSING MEDICAL TECHNOLOGY erative wound infection and mortality following colon surgery.
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The Diagnostic and Therapeutic Technology Assessment Program of the American Medical Association was initiated in 1982 to answer questions regarding the safety and effectiveness of medical technologies. The Health Care Financing Administration, Blue Cross and Blue Shield Association and member plans, *
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It is also used to generate forecasts, plans, problem definitions, programs and policies, summaries of current knowledge, and selections from alternatives (Olsen, 1982~. For health issues, the Delphi technique has been used to obtain estimates, where empirical data are insufficient, of influASSESSING MEDICAL TECHNOLOGY enza epidemic parameters (Schoenbaum et al., 1976b)
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. ~ , , ~ ^ the National institutes of Health (consensus Development Conferences is to evaluate the available scientific information on biomedical technologies and to produce consensus statements for use by health professionals and the public.
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Among the samples of five physician specialties targeted for the CT scan conference, awareness that the conference was being held ranged between 11 and 37 percent, and awareness of its ASSESSING MEDICAL TECHNOLOGY conclusions ranged from 1 to 15 percent. Among the samples of six physician specialties targeted for the hip joint conference, awareness that the conference was being held ranged between 7 and 21 percent, and awareness of its conclusions ranged from 0 to 10 percent.
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From page 133... ...
In so doing, expert panels may render recommendations relying to some extent on suggestive but not rigorously founded clinical evidence, e.g., derived from weaker epidemiologic studies as op posed to randomized clinical trials. One recommendation of the NIH consensus panel on lowering blood cholesterol to lower dietary cholesterol for all Americans age two onward—may have been such an instance.
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Panelists may amend the list of indications and then rate the clinical appropriASSESSING MEDICAL TECHNOLOGY ateness of each and select the most frequently used of the lot. At the consensus meeting, panelists discuss and rate in at least two rounds those indications that showed high disagreement in their initial ratings of clinical appropriateness and that account for the majority of the procedures.
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From page 135... ...
The advantages of computer conferencing participants' independence of space and time constraints and automatic recording of data, communications, and other transactions may be quite suitable for engaging group judgment efforts in medical technology assessment and for documenting, evaluating, and improving the group deliberative process. Strengthening Group judgment Efforts The current level of group judgment efforts to determine how best to put medical technologies to use is not commensurate with the effort and care devoted to developing these technologies.
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ASSESSING MEDICAL TECHNOLOGY COST-EFFECTIVENESS AND COST-BENEFIT ANALYSES* The Office of Technology Assessment defined the terms cost-effectiveness analysis (CEA)
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It reported that the considerable growth in the CEA/CBA literature over the period surveyed was more rapid in medical than in nonmedical journals and that a preference appeared to be emerging for CEA over CBA. This study also found 137 that while the number of all types of CEA/ CBA studies increased, those related to diagnosis and treatment technologies showed considerable increases in prominence relative to those on preventive health.
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. A wide variety of evaluative approaches, including randomized clinical trials and epidemiological studies, form the basis for assessing effectiveness of medical technology.
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Public societal benefits and costs often differ substantially from private benefits and costs. For the public policymaker, societal benefits sought may be primarily in cost reduction of improved accessibility of health care services.
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In any actual decision, however, policymakers should consider also social effects such as equity and political importance (Banta et al., 1981~. Social and ethical consequences of medical technology are increasingly being questioned in such applications as support systems for prolonging life in incurable termiASSESSING MEDICAL TECHNOLOGY nal patients, organ transplants (e.
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Usually the assessment of diagnostic technology separates the evaluation of the cost-effectiveness of the process in achieving its diagnostic objectives from the cost-effectiveness of subsequent treatment technologies which have a different set of specific objectives (McNeil, 1979~. A variety of diagnostic and screening tests have been studied, including hypertensive renovascular disease (McNeil et al., 1975)
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However, a benefit-cost ratio (B/C) would yield the following results: ASSESSING MEDICAL TECHNOLOGY Program 13 $3 million = 1 5 $2 million Now, program A is clearly preferred.
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From page 143... ...
For missing or uncertain data, an appropriate group of experts, selected carefully to minimize bias, can use consensus development techniques to provide credible estimates of missing data. Then by studying a variety of assumptions for important variables and by using middle, low, and high values to appropriately express realistic, optimistic, and pessimistic scenarios, the policymaker may estimate the limits of errors in projected costs and establish minimum, maximum, and break-even costs for the program.
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CEA/CBA can be useful for planning and usually emASSESSING MEDICAL TECHNOLOGY ploy sensitivity analysis for uncertainties of the future, such as by testing the effects of a range of discount rates on results. Better methodology is still needed, for such tasks as valuing changes in health status.
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From page 145... ...
A medical technology is not a static item; it takes a variety of forms depending on who is using it, on whom, when, and how. A diagnostic test can be preceded or followed by other tests; can be used at different times in the course of a patient's condition; can be used on patients with different types of problems, different ages, and different risk factors; can be used with different techniques; can be interpreted against different criteria; and can be followed by different therapies.
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From page 146... ...
For this source, there are usually no concurrent (much less randomized) controls, ASSESSING MEDICAL TECHNOLOGY and issues like age, risk factors and the type of delivery system, even issues like which women are getting the test and how frequently, can rarely be studied with any precision.
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From page 147... ...
The assessment of the frequency of the Pap smear is a good example. A mathematical
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From page 148... ...
Mathematical models can be created to describe the hypothesized dynamics, parameters can be fitted, and results can be predicted. The extent to which the values predicted by the ASSESSING MEDICAL TECHNOLOGY model fit the observations provides evidence about the validity of the hypothesis.
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Like experimental and epidemiological methods, mathematical models can have varying degrees of detail and complexity, and their development can require different amounts of time and money. For example, to study the question of breast cancer screening in high-risk women, one might use a very simple mathematical model such as assuming that a positive family history of breast cancer implies a relative risk of two, and then multiplying the pertinent results of the HIP study by two.
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From page 150... ...
Changes ASSESSING MEDICAL TECHNOLOGY in the technology itself; the age, risk, and behavior of the patients; the institutional setting; and many other factors can make comparisons meaningless. Beyond this, the random component to the outcomes of any clinical trial can prevent the predicted and observed outcomes from matching, even if a model is perfect.
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From page 151... ...
METHODS OF TECHNOLOGY ASSESSMENT models and an erroneous model will pass a first-order validation. Because of this, to the greatest extent possible, models should be based on observations from welldesigned studies rather than subjective judgments, and the results of a mathematical model should never be preferred to the results of actual clinical experiments, when they are available.
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From page 152... ...
The results of this research already are available for application to the evaluation of medical technologies. In medicine the main needs are not to ASSESSING MEDICAL TECHNOLOGY improve the techniques, but to apply them responsibly.
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METHODS OF TECHNOLOGY ASSESSMENT by asking that each report of a technology assessment employing a mathematical model contain the following elements: 1. a statement of the problem; 2.
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This section was written by Morris Collen and Lincoln Moses. ASSESSING MEDICAL TECHNOLOGY which the public increasingly embraces "holistic" or "alternative" medicine that employs less technology and uses the placebo effect, biofeedback, meditation, visualization, and forms of body manipulation as modes of self-therapy.
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From page 155... ...
identifying those who make the decisions about whom to treat. End-stage renal disease (ESRD)
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From page 156... ...
The probASSESSING MEDICAL TECHNOLOGY lem, however, is that, in many respects, social and medical criteria are inextricably intertwined. People of low socioeconomic status are likely to be in poorer health and have multiple diseases.
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From page 157... ...
In one approach investigators used the Delphi technique to examine such matters as systematic control of behavior, reproductive engineering, genetic screening, extension of life, and data bank-computer technology. In a second approach researchers used a case-study method for a colloquium to develop a historical and sociological perspective on recent advances in biomedical and behavioral research and services.
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From page 158... ...
Second, to waste information that can benefit future patients is unethical, especially if that information has been obtained under conditions of risk. We find it convenient to treat the ethical issues as those that attach to three temporal ASSESSING MEDICAL TECHNOLOGY phases: initiation, conduct, and termination.
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From page 159... ...
METHODS OF TECHNOLOGY ASSESSMENT tion is to quit too soon before an obtainable conclusive answer is on hand. Some of the controversy over the University Group Diabetes Program (UGDP)
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From page 160... ...
survey of CEA/CBA practitioners raised this complaint. Similarly, perusal of OHTAOMAR reviews repeatedly point to the paucity of randomized clinical trials of other cogent primary data (NIH, 1983, 1984; Fink et al., 1984; K
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161 only; METHODS OF TECHNOLOGY ASSESSMENT 2. house testing and house deleading 3.
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Costs (1~: In each year of the program, 17,000 children will be screened ($8 each) , 6 percent of which will be treated (of treated: 65 percent with followASSESSING MEDICAL TECHNOLOGY up and 35 percent with chelation therapy)
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METHODS OF TECHNOLOGY ASSESSMENT Benefits (1)
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From page 164... ...
Eddy. ASSESSING MEDICAL TECHNOLOGY As an example, imagine an asymptomatic, average-risk, 40-year-old woman who had a Pap smear a year ago, and suppose we wanted to estimate the effect of repeating the Pap smear today on the chance she will die of cervical cancer, or on her life expectancy.
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From page 165... ...
This last expression must be multiplied by FN, the chance that that Pap smear was falsely negative and missed it. The expression rat')
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From page 166... ...
ASSESSING MEDICAL TECHNOLOGY The calculations indicate that the 3-year Pap smear is about 99 percent as effective as an annual Pap smear. If the 40-year-old, average-risk woman in the original example postponed her Pap smear another 2 years, the increased annual risk she would run of dying of cervical cancer would be on the order of l per lOO,000, about the same as the risk of death from one round-trip transcontinental airplane flight.
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1976. Randomized clinical trials: Perspectives on some recent ideas.
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From page 168... ...
1984. Reporting clinical trials in general surgical journals.
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1981. Fundamentals of Clinical Trials, ix, 225.
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From page 170... ...
1983. The potential use of Health Care Financing Administration data tapes for health care services research.
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Report of the National Committee on Vital and Health Statistics. Public Health Service, DHHS Publ.
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From page 172... ...
Report of the National Committee on Vital and Health Statistics. Public Health Service, DHHS Publ.
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From page 173... ...
1978. Problems of spectrum and bias in evaluating the efficacy of diagnostic tests.
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From page 174... ...
1983. Clinical Trials: Issues and Approaches, pp.
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1982b. Evaluation of NIH Consensus Development Process.
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