The development of QUADAS: a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews

We conducted a Delphi procedure to develop the quality assessment tool by refining an initial list of items. Members of the Delphi panel were experts in the area of diagnostic research. The results of three previously conducted reviews of the diagnostic literature were used to generate a list of potential items for inclusion in the tool and to provide an evidence base upon which to develop the tool.A total of nine experts in the field of diagnostics took part in the Delphi procedure. The Delphi procedure consisted of four rounds, after which agreement was reached on the items to be included in the tool which we have called QUADAS. The initial list of 28 items was reduced to fourteen items in the final tool. Items included covered patient spectrum, reference standard, disease progression bias, verification bias, review bias, clinical review bias, incorporation bias, test execution, study withdrawals, and indeterminate results. The QUADAS tool is presented together with guidelines for scoring each of the items included in the tool.This project has produced an evidence based quality assessment tool to be used in systematic reviews of diagnostic accuracy studies. Further work to determine the usability and validity of the tool continues.Systematic reviews aim to identify and evaluate all available research evidence relating to a particular objective. [1] Quality assessment is an integral part of any systematic review. If the results of individual studies are biased and these are synthesised without any consideration of quality then the results of the review will also be biased. It is therefore essential that the quality of individual studies included in a systematic review is assessed in terms of potential for bias, lack of applicability, and, inevitably to a certain extent, the quality of reporting. A formal assessment of the quality of primary studies included in a review allows investigation of the effect of different biases and sources of variation on study results.