Insufficient follow-up of test results is a known contributor to missed and delayed diagnosis. This observational study used a trigger tool to detect diagnostic delays related to chest imaging follow-up. Investigators used an automated algorithm to identify chest imaging cases that potentially had a follow-up delay. A clinician then reviewed the medical records for a random sample of cases identified by the trigger tool and a reference set of cases involving patients with abnormal test results but no delays. They found that the trigger tool had 99% sensitivity and 38% specificity in detecting delays in follow-up of abnormal chest imaging. The authors suggest that this trigger tool may help identify patients at risk for diagnostic delay following abnormal chest imaging. A WebM&M commentary discussed delayed follow-up of a diagnostic test.