Once the evidence has been found, it needs to be critically appraised for its reliability and usefulness. Psychiatrists need to be able to assess the scientific value and clinical importance of a study. This requires a range of epidemiological and biostatistical skills that have not traditionally been considered to be key skills for psychiatrists. In the United Kingdom, the Royal College of Psychiatrists introduced in 1999 a new part of the main professional examination that is designed to test these skills, recognizing their fundamental importance for clinical psychiatrists. (22)
Structured critical appraisal is an active process that involves a systematic assessment of the key methodological aspects of the paper. In particular, critical appraisal focuses systematically on those aspects of the study methodology that are most likely to lead to unreliability of results. A number of checklists, designed to make the appraisal quicker and more systematic, have been produced for different research study designs.(23) For example, the critical appraisal of a systematic review involves an assessment of those aspects of methodology described in Cd.a.2t§1..6.:1.1...2,. A commonly used checklist for systematic reviews is shown in T§ble 2.
Table 2 Checklist to assist the critical appraisal of a systematic review
Using the checklist, the review can be quickly critically appraised. It is a review of the effectiveness of antidepressants in dysthymia and so appears relevant to the clinical question. The authors have only included randomized controlled trials, and this will make systematic error less likely and improve the reliability of the review. The literature search strategy is clearly documented and included electronic databases (Medline, Psyclit, Embase, Lilacs and the Cochrane Library), handsearching of journals, and correspondence with researchers active in the field. The quality of the randomized controlled trials was rated both from the description of the allocation of treatment and by assessing other methodological issues such as whether the primary analysis was done as an intention-to-treat analysis and the degree of blinding of the clinician and patient. It can be concluded that the reviewers have made a reasonable effort to identify the primary studies, although it is possible that other studies, perhaps with negative results, have not been published (publication bias, see Chapter,6.J .1.2).
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