Table 1 Classification of evidence per article
Level of evidence | Interventional research | Studies concerning diagnostic accuracy | Studies on complications or side effects, etiology, prognosis |
|---|---|---|---|
A1 | Systematic review/meta-analysis of at least 2 independently performed level A2 studies | ||
A2 | Double-blind controlled randomized comparative clinical trial of good study quality with an adequate number of study participants | Diagnostic test compared to reference test; criteria and outcomes defined in advance; assessment of test results by independent observers; independent interpretation of test results; adequate number of consecutive patients enrolled; all patients subjected to both tests | Prospective cohort with sufficient amount of study participants and follow-up, adequately controlled for confounders; selection in follow-up has been successfully excluded |
B | Comparative studies, but without all the features mentioned for level A2 (including patient-control studies, cohort studies) | Diagnostic test compared to reference test, but without all the features mentioned in A2 | Prospective cohort study, but without all the features mentioned for level A2 or retrospective cohort study or case-control study |
C | Noncomparative studies | ||
D | Expert opinion | ||