Verification problems in diagnostic accuracy studies: consequences and solutions

SUMMARY POINTS In studies of diagnostic accuracy studies, ideally all patients undergoing the index test are verified by the reference standard This is not always possible, and incomplete or improper disease verification is one of the major sources of bias in diagnostic accuracy studies Partial verification bias occurs when not all patients are verified by the reference standard; instead, disease verification is related to other, previous (index) test results or patient characteristics. Multiple imputation methods can be used to correct for the partial verification bias An alternative reference test may be used for those cases where verification with the preferred reference test is not possible. This can result in differential verification bias if the results of both reference tests are treated as equal and interchangeable, when they are really of different quality or define the target condition differently. Instead, the estimated accuracy of the diagnostic index test should be reported separately for each reference test