Objective: We aimed to provide simple methods for calculating expected sensitivity and specificity when an adjunctive test is added to a conventional test.
Study design: Use of adjunctive methods for the triage of women with cervical abnormalities produces an apparent gain in sensitivity over Papanicolaou cytologic testing alone. This increase in sensitivity can be misleading, even if deemed significant by results of a statistical test. Combined testing prevents a loss in specificity but sometimes offers no real gain in sensitivity. A nominal increase in sensitivity always occurs by chance whenever an adjunctive test is used in parallel with a conventional one, even if the new test is totally random with respect to the disease being evaluated.
Results: Gains in sensitivity and losses in specificity have to be gauged against expected levels of these parameters when a random adjunctive test is coupled with Papanicolaou screening and not gauged against the performance of cytologic testing alone.
Conclusion: We provide simple formulas for calculating the expected sensitivity and specificity in conditions of combination testing to provide more realistic baselines for assessment of the screening efficacy contributed by the adjunctive test.