Fig. 2

a Risk of bias graph. b Risk of bias summary. Methodological quality was assessed on four key domains (1. patient selection, 2. index test, 3. reference standard and 4. flow and timing). Therein none of the studies was assessed as low risk of bias in all of the four key domains. Applicability concerns were assessed in three key domains (1. patient selection, 2. index test, 3. reference standard) with the QUADAS-2 tool. Applicability concerns were generally lower