160 Chapter 4 Possible required knowledge components ↓ Role in guideline panel Health care provider Health care consumer Methodologist Guideline panel chair Treatment following a test result may influence surrogate/intermediate outcomes, related to patient relevant outcomes Treatment following a test result may or may not be effective in improving patient relevant outcomes Treatment following a test result may have side effects, adverse events, and complications Treatment following a test result has costs, which may be direct and/or indirect and medical and/or non-medical Medical test evaluation Analytical performance of a test is the ability to correctly detect or measure a measurand (trueness/validity, imprecision, limits of detection, cross-reactivity) Clinical performance of a test is the ability of a test to correctly classify those with and without the target condition (also called diagnostic accuracy) Diagnostic accuracy measures can be determined based on comparisons between the index test (test of interest) and reference test (also called reference standard, this may be the gold standard) Diagnostic accuracy measures can be derived from a 2x2 table in which patients with and without the disease of interest are classified according to their test result Diagnostic accuracy measures include true positives, true negatives, false positives, false negatives, inconclusive test results, sensitivity and specificity, positive and negative predictive value, likelihood ratio for positive and negative tests, diagnostic odds ratio, ROC-curve, and area under the curve Test accuracy describes the performance of a test in specific circumstances (and may therefore vary), e.g., in specific pre-test probabilities (prevalence of the disease) Positive and negative test results are defined based on a threshold for test positivity. Changing the threshold may change the test results Clinical effectiveness (also called clinical utility) of a test is the ability of a test to improve patient relevant outcomes Clinical effectiveness of a test is evaluated by evaluating the test-treatment pathway Clinical effectiveness of a test can be evaluated directly by performing a diagnostic RCT Clinical effectiveness of a test is mostly evaluated indirectly by assessing the different steps of the test-treatment pathway
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