Current methods of the US Preventive Services Task Force - A review of theprocess

The U.S. Preventive Services Task Force (USPSTF/Task Force) represents one of several efforts to take a more evidence-based approach to the developmen t of clinical practice guidelines. As methods have matured for assembling a nd reviewing evidence and for translating evidence into guidelines, so too have the methods of the USPSTF. This paper summarizes the current methods o f the third USPSTF, supported by the Agency for Healthcare Research and Qua lity (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 poten tially effective preventive service. It focuses its reviews on the question s and evidence most critical to making a recommendation. It uses analytic f rameworks to specify the linkages and key questions connecting the preventi ve service with health outcomes. These linkages, together with explicit inc lusion criteria, guide the literature searches for admissible evidence. Once assembled, admissible evidence is reviewed at three strata: (1) the in dividual study, (2) the body of evidence concerning a single linkage in the analytic framework, and (3) the body of evidence concerning the entire pre ventive sen ice. 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 mu st 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 t he connection between the preventive service and health outcomes is uncerta in. For services supported by overall good or fair evidence, the Task Force use s outcomes tables to help categorize the magnitude of benefits, harms, and net benefit fi-om 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 ben efit to make a recommendation, coded as a letter: from A (strongly recommen ded) to D (recommend against). It gives an I recommendation in situations i n which the evidence is insufficient to determine net benefit. The third Task Force and the EPCs will continue to examine a variety of met hodologic issues and document work group progress in future communications.