“…Two studies showed unclear risk of bias in the reference standard 22,44 and two studies showed unclear risk of bias in the flow timing 39,45 . Two studies have indicated high risk of bias in the patient selection in the applicability criteria 50,51 , and two studies demonstrated a high risk of bias in evaluating the index test 48,65 . In the other studies, there were some unclear applicability criteria in the index test and reference standard 19,21,[23][24][25][26]29,30,32,34,35,38,40,42,43,46,47,49,53,54,57,64,[67][68][69] .…”