Systematic reviews of diagnostic research. Considerations about assessmentand incorporation of methodological quality

The aim of this paper is to provide a theoretical background for performing and reading systematic reviews of diagnostic studies. We first discuss ite ms for assessment of methodological quality in diagnostic studies and then present methods on how to incorporate these quality measures in systematic reviews. The items of internal validity determine whether the presented res ults of the individual studies are unbiased and can be trusted. Items of ex ternal validity determine to what extent the results are applicable outside the population in which the study was performed. The issues concern the ad equacy of the study population, the performance and interpretation of the d iagnostic tests and the presentation of the results. Several methods exist for incorporation of issues of methodological quality into systematic revie ws, such as subgroup analyses, meta-regression analysis, and methodological scores. Publications of diagnostic studies should provide sufficient infor mation to enable assessment of the methodological quality. Furthermore, pub lication of results of subgroup analyses should be promoted. Methodological criteria lists might help to improve the quality of systematic reviews of diagnostic research. With the items of methodological quality in mind the g eneral practitioner might be better equipped to critically read and interpr et diagnostic reviews.