Cochrane's Editor-in-Chief endorsed the QUADAS-C risk of bias tool as optional for prospective authors of Cochrane Diagnostic Test Accuracy (DTA) Reviews addressing comparative questions following a recommendation from the Methods Executive and relevant experts from across Cochrane and the diagnostic field. This tool helps DTA review authors to assess the risk of bias in comparative DTA studies, i.e. studies in which two or more index tests are directly compared in terms of their accuracy performance. These studies are susceptible to various sources of bias, such as confounding and problems with how the index tests are implemented or used by study authors, which may go undetected in reviews lacking adequate methods to identify such problems.
The QUADAS-C tool is an extension of QUADAS-2, a quality assessment tool already recommended for Cochrane DTA Reviews and currently included in the Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy. Using QUADAS-2 allows review authors to assess the risk of bias and applicability of the accuracy estimate of a single diagnostic test. Using QUADAS-C in addition will also allow reviewers to assess the risk of bias in (absolute or relative) difference in accuracy, which is relevant for drawing conclusions on whether one diagnostic test has a superior or equal performance to another test.
What types of reviews is this tool for?
Cochrane DTA Reviews assess the accuracy of one or more diagnostic tests. A comparison of the accuracy of these tests, although a separate question, is also frequently done in DTA reviews. QUADAS-C can be used in DTA reviews addressing these comparative accuracy questions. Prior to the arrival of QUADAS-C, DTA reviews usually reported results of QUADAS-2 assessments, but it was not always clear whether this also applied to the comparison of accuracy. Using QUADAS-C in DTA reviews is expected to improve the distinction between the risk of bias judgments of single test accuracy estimates and those of comparative accuracy estimates. Currently, RevMan does not yet support the use of QUADAS-C. For the time being, authors can include QUADAS-C risk of bias tables and graphs in their reviews using the resources below.
About the project
QUADAS-C was developed by a group of 24 methodologists and experts in diagnostic test evaluation, of whom many had also been involved in the development of QUADAS-2. The tool was developed through a four-round Delphi process, a face-to-face consensus meeting, and a pilot study among potential users. The project was led by Bada Yang and Mariska Leeflang (Amsterdam UMC; Cochrane Screening and Diagnostic Tests Methods Group).
Learn more about the QUADAS-C tool and how it can be used:
- The official QUADAS-C website contains the following resources:
- The QUADAS-C tool.
- Guidance on how to use QUADAS-C.
- Template for tabular displays of QUADAS-C assessments (for use as tables in the review).
- Template for graphical displays of QUADAS-C assessments (for use as figures in the review).
- Paper introducing QUADAS-C published in Annals of Internal Medicine.
- The Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy, chapter 9: Assessing risk of bias and applicability
- A webinar on QUADAS-C will become available on the Cochrane Training website.
If you have any questions about QUADAS-C, please contact Bada Yang (b.d.yang@umcutrecht.nl)
Written by Bada Yang and posted by Ingrid Arevalo-Rodriguez