Quality assessment of diagnostic before-after studies: development of methodology in the context of a systematic review

The QUADAS tool was assessed for use in the review by two systematic reviewers with in-depth knowledge of the clinical area being reviewed and the types of studies being found in the searches that could answer the clinical question. Modifications were made following discussion as considered appropriate.Two QUADAS questions were removed altogether and. four additional questions were developed to capture additional quality issues not addressed by QUADAS. However, the developed checklist only partially helped to discern implications of the study designs on the results given.The division between topic-specific and more generic quality items of relevance to diagnostic before-after studies is important. With more time, further work could have been done to create a better quality assessment tool, for example by incorporating some of the issues mentioned in previous work in this area. This paper is a discussion around quality assessment and is intended to offer insights into the types of issues that should be assessed. A quality assessment tool for diagnostic before-after studies that incorporates items from QUADAS and published theory needs to be further developed and validated.The evaluation of diagnostic technologies includes assessment of test accuracy and clinical, process or economic outcomes following testing (see additional file 1)[1]. The impact of a test depends on a variety of factors in addition to test accuracy including; interpretation of tests results, the possibility that the new information does not contribute sufficiently to cross a treatment threshold, clinician awareness of availability of cost-effective treatments, lack of patient access to treatments, acceptability of treatments to patients and the possibility that the patient is already receiving optimal care[2].Once test results arrive, clinicians use the information to make categorise patients into those with and those without disease, known as the diagnostic yield, and then decisions about treatmen