Three principles to define the success of a diagnostic study could be identified

Objective: Diagnostic studies are typically studies with two endpoints, sensitivity and specificity. To define the success of a diagnostic study, results for these two endpoints have to be combined in an appropriate manner.

Study design and setting: Identification of criteria to define the success of a diagnostic study on a single binary test and investigation of common statistical approaches in relation to these criteria.

Results: Three criteria for defining the overall success of a diagnostic study could be identified: a strong criterion, a liberal criterion, and a weak criterion. The strong criterion can be implemented by comparing the lower bounds of the confidence intervals for sensitivity and specificity with prespecified target values, as is typically done in many diagnostic studies. The liberal criterion allows a clinically meaningful compensation between sensitivity and specificity and can be implemented in different ways. If the liberal criterion is applied instead of the strong criterion, this can lead to a substantial reduction in the sample size required for a diagnostic study. The weak criterion is not very adequate for defining the success of a diagnostic study.

Conclusion: When planning and analyzing diagnostic studies, the criterion to define the success of the study should be clearly prespecified. The results of the statistical approach taken should be interpreted in accordance with this criterion. This ensures coherence of results and prevents unnecessarily large sample sizes. The liberal criterion should be paid more attention to in the future.