Comparing sensitivity and specificity of medical imaging tests when verification bias is present: The concept of relative diagnostic accuracy

Medical imaging plays a key role in all stages of cancer management. In evaluating a new imaging modality, the optimal design involves a comparison with standard test results as well as a gold standard, such as a pathological evaluation to determine disease status. However, when both the standard and experimental test results are negative, a gold standard may not always be performed, especially if it involves an invasive and/or costly procedure. In this situation, true disease status cannot be verified, which creates an estimation problem for sensitivity and specificity. The aim of this article is to present the concept of relative accuracy which permits to remove the bias when only patients with at least one positive test receive the gold standard.