Skip to main content

Table 1 Classification of evidence per article

From: Bologna guidelines for diagnosis and management of adhesive small bowel obstruction (ASBO): 2017 update of the evidence-based guidelines from the world society of emergency surgery ASBO working group

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