2.2 Identification and selection of COSs.
COMET has successfully brought together the international COS literature in an online database (http://www.comet-initiative.org/studies/search).8 We conducted a comprehensive search of COMET database on December 20, 2019, one reviewer (Y.G. or J.Y.S.) exported the entire registered COS study records from the COMET database. The full-text publications that met our inclusion criteria were then filtered. A regularly updated systematic review of COSs was screened to identify OG COSs as a supplement.8 The list of COSs was reviewed by a COS/methodology expert (J.H.Z). No restriction was placed on language.