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. (C) RSNA, 2009