Proof and policy from medical research evidence.

When judging the benefits and harms of health care and predicting patient prognosis, clinicians, researchers, and others must consider many types of evidence. Medical research evidence is part of the required knowledge base, and practitioners of evidence-based medicine must attempt to integrate the best available clinical evidence from systematic research with health professionals' expertise and patients' rights to be informed about diagnostic and therapeutic options available to them. Judging what constitutes sound evidence can be difficult because of, among other things, the sheer quantity, diversity, and complexity of medical evidence available today; the various scientific methods that have been advanced for assembling, evaluating, and interpreting such information; and the guides for applying medical research evidence to individual patients' situations. Recommendations based on sound research can then be brought forward as either guidelines or standards, and criteria exist by which valid guidelines and standards can be developed and promulgated. Nonetheless, gaps and deficiencies exist in current guidelines and in the methods for finding and synthesizing evidence. Interpreting and judging medical research involves subjective, not solely explicit, processes. Thus, developments in evidence-based medicine are an aid, but not a panacea, for definitively establishing benefits and harms of medical care, and the contributions that medical research evidence can make in any clinical or legal situation must be understood in a context in which judgment and values, understanding of probability, and tolerance for uncertainty all play a role.

Current methods of the US Preventive Services Task Force: a review of the process.

The U.S. Preventive Services Task Force (USPSTF/Task Force) represents one of several efforts to take a more evidence-based approach to the development of clinical practice guidelines. As methods have matured for assembling and reviewing evidence and for translating evidence into guidelines, so too have the methods of the USPSTF. This paper summarizes the current methods of the third USPSTF, supported by the Agency for Healthcare Research and Quality (AHRQ) and two of the AHRQ Evidence-based Practice Centers (EPCs). The Task Force limits the topics it reviews to those conditions that cause a large burden of suffering to society and that also have available a potentially effective preventive service. It focuses its reviews on the questions and evidence most critical to making a recommendation. It uses analytic frameworks to specify the linkages and key questions connecting the preventive service with health outcomes. These linkages, together with explicit inclusion criteria, guide the literature searches for admissible evidence. Once assembled, admissible evidence is reviewed at three strata: (1) the individual study, (2) the body of evidence concerning a single linkage in the analytic framework, and (3) the body of evidence concerning the entire preventive service. For each stratum, the Task Force uses explicit criteria as general guidelines to assign one of three grades of evidence: good, fair, or poor. Good or fair quality evidence for the entire preventive service must include studies of sufficient design and quality to provide an unbroken chain of evidence-supported linkages, generalizable to the general primary care population, that connect the preventive service with health outcomes. Poor evidence contains a formidable break in the evidence chain such that the connection between the preventive service and health outcomes is uncertain. For services supported by overall good or fair evidence, the Task Force uses outcomes tables to help categorize the magnitude of benefits, harms, and net benefit from implementation of the preventive service into one of four categories: substantial, moderate, small, or zero/negative. The Task Force uses its assessment of the evidence and magnitude of net benefit to make a recommendation, coded as a letter: from A (strongly recommended) to D (recommend against). It gives an I recommendation in situations in which the evidence is insufficient to determine net benefit. The third Task Force and the EPCs will continue to examine a variety of methodologic issues and document work group progress in future communications.

Screening and treating adults for lipid disorders.

CONTEXT: Screening and treatment of lipid disorders in people at high risk for future coronary heart disease (CHD) events has gained wide acceptance, especially for patients with known CHD, but the proper role in people with low to medium risk is controversial. OBJECTIVE: To examine the evidence about the benefits and harms of screening and treatment of lipid disorders in adults without known cardiovascular disease for the U.S. Preventive Services Task Force. DATA SOURCES: We identified English-language articles on drug therapy, diet and exercise therapy, and screening for lipid disorders from comprehensive searches of the MEDLINE database from 1994 through July 1999. We used published systematic reviews, hand searching of relevant articles, the second Guide to Clinical Preventive Services, and extensive peer review to identify important older articles and to ensure completeness. DATA SYNTHESIS: There is strong, direct evidence that drug therapy reduces CHD events, CHD mortality, and possibly total mortality in middle-aged men (35 to 65 years) with abnormal lipids and a potential risk of CHD events greater than 1% to 2% per year. Indirect evidence suggests that drug therapy is also effective in other adults with similar levels of risk. The evidence is insufficient about benefits and harms of treating men younger than 35 years and women younger than 45 years who have abnormal lipids but no other risk factors for heart disease and low risk for CHD events (less than 1% per year). Trials of diet therapy for primary prevention have led to long-term reductions in cholesterol of 3% to 6% but have not demonstrated a reduction in CHD events overall. Exercise programs that maintain or reduce body weight can produce short-term reductions in total cholesterol of 3% to 6%, but longer-term results in unselected populations have found smaller or no effect. To identify accurately people with abnormal lipids, at least two measurements of total cholesterol and high-density lipoprotein cholesterol are required. The role of measuring triglycerides and the optimal screening interval are unclear from the available evidence. CONCLUSIONS: On the basis of the effectiveness of treatment, the availability of accurate and reliable tests, and the likelihood of identifying people with abnormal lipids and increased CHD risk, screening appears to be effective in middle-aged and older adults and in young adults with additional cardiovascular risk factors.

Health outcomes methodology symposium: summary and recommendations.

BACKGROUND: Interest in the philosophy and techniques of the assessment of health outcomes has burgeoned, prompting research funding agencies and others to examine traditional and emerging methods for outcome measurement. OBJECTIVES: This report summarizes the presentations and discussions at and research recommendations stemming from an invitational symposium on health outcomes methodology convened in September 1999. RESEARCH DESIGN: The summary is based on the preliminary drafts of all formal reports and discussions, transcripts of all presentations and plenary discussions, and notes from breakout groups. RESULTS AND CONCLUSIONS: Existing health outcomes measures drawn from classic test theory and emerging approaches based on item response theory offer exciting opportunities for appreciably expanded applications in biomedical and health services research, clinical practice and decision making, and policy development. The major research agenda reflects the significance of this field of endeavor, its widening acceptance both at home and abroad, and its increasing applicability to many different patient and user communities. Of particular moment are the following: (1) refining and expanding of measurement techniques that rely on item response theory and making these approaches more understandable to potential users; (2) improving measurement tools to make them more culturally appropriate for diverse populations and more conceptually and psychometrically equivalent across such groups; (3) addressing longstanding issues in preference- and utility-based approaches, particularly in the elicitation of preference responses and scoring instruments; and (4) enhancing the ways in which data from outcomes measurement tools are calibrated against commonly understood clinical and lay metrics, are interpreted, and are made usable for different decision-makers.

Applying cognitive design principles to formatting HRQOL instruments.

Researchers developing or using health-related quality of life (HRQOL) instruments can benefit from knowledge of state-of-the-art formatting methods for self-administered questionnaires. Three objectives in formatting design are: (1) to reduce errors in respondent navigation through the questionnaire that lead to item non-response and question misinterpretation; (2) to reduce respondent and administrative burden; and (3) to enhance respondent motivation in question answering and compliance with the request to participate. Based on an extensive literature review to identify techniques that have been shown to meet these objectives, we developed specific guidelines for HRQOL instruments concerning all aspects of questionnaire formatting. These guidelines represent well-motivated recommendations for improving HRQOL instruments, although their overall impact has not been empirically tested. We applied the guidelines to several HRQOL instruments that are widely used internationally, and obtained approval from the developers for all formatting changes to their instruments. Applying cognitive design principles and empirically substantiated formatting techniques produces an HRQOL instrument formatting with six critical attributes: simple, consistent, organized, natural, clear and attractive. The present paper contributes to the emerging research literature on the cognitive processes by which respondents answer HRQOL questions and demonstrates how 'cognitive aspects of survey methodology' research can improve HRQOL data collection efforts.

Evidence-based practice and nursing: commentary.

With changes in health care, it has become clear that nurses need data to establish evidence for their decisions and interventions. Evidence-based practice involves the use of the best evidence available for making clinical decisions about patient care. The identification of the knowledge base for nursing practice contributes to achieving patient outcomes and making nursing practice credible.