Recommendations for additional imaging in radiology reports: multifactorial analysis of 5.9 million examinations.

PURPOSE To quantify the rates of recommendation for additional imaging (RAI) in a large number of radiology reports of different modalities and to estimate the effects of 11 clinically relevant factors. MATERIALS AND METHODS This HIPAA compliant research was approved by the institutional review board under an expedited protocol for analyzing anonymous aggregated radiology data. All diagnostic imaging examinations (n = 5 948 342) interpreted by radiologists between 1995 and 2008 were studied. A natural language processing technique specifically designed to extract information about any recommendations from radiology report texts was used. The analytic data set included three quantitative variables: the interpreting radiologist's experience, the year of study, and patient age. Categoric variables described patient location (inpatient, outpatient, emergency department), whether a resident dictated the case, patient sex, modality, body area studied, ordering service, radiologist's specialty division, and whether the examination result was positive. A multivariable logistic regression model was used to determine the effect of each of these factors on likelihood of RAI while holding all others equal. RESULTS Recommendations increased during the 13 years of study, with the unadjusted rate rising from roughly 6% to 12%. After accounting for all other factors, the odds of any one examination resulting in an RAI increased by 2.16 times (95% confidence interval: 2.12, 2.21) from 1995 to 2008. As radiologist experience increased, the odds of an RAI decreased by about 15% per decade. Studies that had positive findings were more likely (odds ratio = 5.03; 95% confidence interval: 4.98, 5.07) to have an RAI. The remaining factors also had significant effects on the tendency for an RAI. CONCLUSION The likelihood of RAI increased by 15% for each decade of radiologist experience and roughly doubled over 13 years of study.