Within systematic reviews of diagnostic test accuracy, the QUADAS-C tool can assess risk of bias in test comparisons undertaken in comparative accuracy studies (studies that evaluate two or more index tests). QUADAS-C is an extension of QUADAS-2 (i.e., it is a set of additional questions to each QUADAS-2 domain): meaning that it should be used together with QUADAS-2. Each QUADAS-C domain asks about QUADAS-2 judgments for each test and additional signalling questions that are specific for comparisons (e.g. whether a fully paired or randomized design was used) to produce a risk of bias judgment for the comparison. Like QUADAS-2, QUADAS-C is a generic tool for all systematic reviews of diagnostic test accuracy but can be tailored to a specific review question. 

June 2022: Cochrane endorsed QUADAS-C as optional for prospective authors following a recommendation from the Methods Executive, which was informed by the relevant Methods Group, Cochrane's Methods Support Unit, the Head of Methods and Evidence Synthesis/Deputy Editor-in-Chief, a Cochrane Review Group representative and the Methods Executive representative on Cochrane's Editorial Board. 

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