Unexpected findings at imaging: Predicting frequency in various types of studies

Objective: The objective was to evaluate the prevalence and associated variables of unsuspected findings from imaging tests in clinical practice.Material and Methods: Cross-sectional study of patients referred for an imaging test in 2006. Two independent radiologists classified the imaging tests according to the presence or absence of an unexpected finding in relation with the causes that prompted the test (kappa = 0.95). A thorough chart review of these patients was carried out as a quality control.Results: Out of 3259 patients in the study, 488 revealed unsuspected findings (15.0%). The prevalence of abnormal findings varied according to age: from 20.4% (150/734) in the over 74-group to 9.0% (76/847) in the under 43-group. The largest prevalence was in the category of infectious diseases (14/49, 28.6%) and in CT (260/901, 28.9%) and ultrasound (138/668, 20.7%). Studies showing moderate clinical information on the referral form were less likely to show unexpected findings than those with null or minor information (OR 0.51; 95% CI 0.36–0.73).Conclusion: Clinicians should expect the frequency of diseases detectable by imaging to increase in the future. Further research with follow-up of these findings is needed to estimate the effect of imaging technologies on final health outcomes.