104 Chapter 3 few randomised controlled trials on the value of test-treatment pathways for patientrelevant outcomes [9]. Evaluating the value of diagnostic tests on patient-relevant outcomes in CPGs is thus complex since it requires integration of various pieces of evidence for the different links in a chain (see figure 1). In the GRADE approach for diagnostic tests and test strategies, the first step is to formulate the clinical question, including definition of patient-important outcomes and description of the aim of the test (add-on, replacement or triage). The next step is to assess diagnostic accuracy and downstream consequences of testing. These include the burden of the test, clinical management, natural course of the target condition (to estimate the outcomes of patients with a false negative test result), and the link between test result and management (proportion of patients with a certain test result who receive the recommended treatment). Ideally, each evidence component is based on a systematic review of the literature and the certainty in the evidence for each component is determined separately [9].Finally, the evidence components are integrated and the overall certainty in the evidence is assessed [12, 13]. To move from evidence to recommendation, guideline developers use the GRADE evidence-todecision framework [12]. The aim of this study is to assess the extent to which evidence-based CPGs about diagnostic tests cover all relevant test-treatment pathway components. Specific objectives are to assess the types of supporting evidence used for CPG recommendations about diagnostic tests, and to explore determinants of best practices. In the context of CPG development about the value of a diagnostic test, we formulated the following research questions: 1. Which types of evidence (diagnostic accuracy, burden of the test, natural course, treatment effectiveness, link between test result and administration of treatment) are used to support the recommendations? 2. Which factors (e.g. composition of the guideline panel, use of the GRADE approach, methodological quality according to AGREE II’s domain methodology) contribute to completeness of the evidence? 3. To what extent can differences between CPG recommendations be explained by including different types of evidence? Answers to these questions elucidate gaps in the implementation of good CPG development methods when developing recommendations about diagnostic tests and test strategies and can help guideline methodologists in developing strategies to facilitate this process.
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