['This study seeks to determine whether health information exchange reduces repeated diagnostic imaging and related costs in emergency back pain evaluation.', "This was a longitudinal data analysis of health information exchange patient-visit data. All repeated emergency department (ED) patient visits for back pain with previous ED diagnostic imaging to a Memphis metropolitan area ED between August 1, 2007, and July 31, 2009, were included. Use of a regional health information exchange by ED personnel to access the patient's record during the emergency visit was the primary independent variable. Main outcomes included repeated lumbar or thoracic diagnostic imaging (radiograph, computed tomography [CT], or magnetic resonance imaging [MRI]) and total patient-visit estimated cost.", 'One hundred seventy-nine (22.4%) of the 800 qualifying repeated back pain visits resulted in repeated diagnostic imaging (radiograph 84.9%, CT 6.1%, and MRI 9.5%). Health information exchange use in the study population was low, at 12.5%, and health care providers as opposed to administrative/nursing staff accounted for 80% of the total health information exchange use. Health information exchange use by any ED personnel was associated with reduced repeated diagnostic imaging (odds ratio 0.36; 95% confidence interval 0.18 to 0.71), as was physician or nurse practitioner health information exchange use (odds ratio 0.47; 95% confidence interval 0.23 to 0.96). No cost savings were associated with health information exchange use because of increased CT imaging when health care providers used health information exchange.'] Does health information exchange reduce repeated diagnostic imaging for back pain?