Recommendations for Additional Imaging in Radiology Reports: Multifactorial Analysis of 5.9 Million Examinations 1 Christopher L. Sistrom, MD, MPH Keith J. Dreyer, DO, PhD Pragya P. Dang, MD Jeffrey B. Weilburg, MD Giles W. Boland, MD Daniel I. Rosenthal, MD James H. Thrall, MD 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 clini- cally relevant factors. Materials and Methods: This HIPAA compliant research was approved by the insti- tutional review board under an expedited protocol for analyzing anonymous aggregated radiology data. All diag- nostic imaging examinations (n = 5 948 342) interpreted by radiologists between 1995 and 2008 were studied. A natural language processing technique specifically de- signed to extract information about any recommendations from radiology report texts was used. The analytic data set included three quantitative variables: the interpreting ra- diologist’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 multivari- able 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 re- maining 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.  RSNA, 2009 1 From the Departments of Radiology (C.L.S., K.J.D., P.P.D., G.W.B., D.I.R., J.H.T.) and Psychiatry (J.B.W.), Massachusetts General Hospital, Boston, Mass. Received February 3, 2009; revision requested March 20; revision received March 26; accepted May 6; final version ac- cepted May 11. Address correspondence to C.L.S., De- partment of Radiology, University of Florida Health Center, PO Box 100374, Gainesville, FL 32610-0374 (e-mail: sistrc@radiology.ufl.edu ).  RSNA, 2009 ORIGINAL RESEARCH  HEALTH POLICY AND PRACTICE Radiology: Volume 253: Number 2—November 2009 ▪ radiology.rsna.org 453 Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights.