Revisiting the Analogy Between Clinical Trials and Diagnostic Tests by Interpreting a Negative Trial as a Negative Test for Efficacy

Lewis and Viele revisit the analogy between clinical trials and diagnostic tests by interpreting a negative trial as a negative test for efficacy. Clinical trials are designed to detect hypothesized treatment effects in the same way diagnostic tests are designed to detect an abnormality or target illness. A trial's statistical power, namely the probability that it can detect the treatment effect given that the hypothesized effect exists, is analogous to a diagnostic test's sensitivity, namely the probability a positive test result is obtained when the target condition is present. Just as the sensitivity of a diagnostic test can be affected by the severity of illness, an effect called "spectrum bias," the power of a clinical trial, is strongly influenced by the magnitude of the true treatment benefit associated with the experimental treatment.