Background: systematic reviews of diagnostic test accuracy (DTA) studies utilize the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies) tool for risk of bias and applicability assessment. Unfortunately, no comparable instrument exists for systematic reviews of prognostic test accuracy studies. Review authors consequently fall to other tools, such as Quality in Prognosis Studies (QUIPS), developed for prognostic factor studies. Despite its merits, QUIPS does not include all necessary criteria for assessing risk of bias and applicability concerns in prognostic test accuracy reviews. An instrument comparable to the well-known QUADAS-2 would facilitate evaluation and communication.
Objectives: we propose QUAPAS (Quality Assessment of Prognostic Accuracy Studies): an extension of the QUADAS-2 tool to assess risk of bias in systematic reviews of prognostic test accuracy studies.
Methods: a group of review authors and methodologists mapped the six domains of the QUIPS tool (study participation, study attrition, prognostic factor measurement, outcome measurement, study confounding, statistical analysis and reporting) to the four domains of QUADAS-2 (patient selection, index tests, reference standard, flow and timing). We applied new and modified signalling questions, derived from relevant items of QUIPS, to each of the four QUADAS-2 domains.
Results: two independent review authors are piloting QUAPAS to explore whether the modified tool can better facilitate quality assessment in the setting of prognostic accuracy studies. Following good agreement, we will apply QUAPAS to rate all included studies of a prognostic accuracy systematic review.
Conclusions: by mapping the necessary domains of QUIPS to QUADAS-2, QUAPAS incorporates the key criteria for risk-of-bias assessment of prognostic accuracy studies, also addressing concerns of applicability. The new tool provides reviewers of prognostic accuracy studies with a familiar and easy to interpret instrument at the same calibre as QUADAS-2 for DTA reviews.
Patient or healthcare consumer involvement: the QUAPAS tool provides a more robust quality assessment tool for systematic reviews of the prognostic test accuracy studies that facilitate evidence-based decision making for prognostic tests in healthcare.