Original Research A drug-drug interaction knowledge assessment instrument for health professional students: A Rasch analysis of validity evidence Terri L. Warholak, Ph.D., R.Ph. a,c, * , J. Michael Menke, M.A., D.C., Ph.D. Candidate b , Lisa E. Hines, Pharm.D. c , John E. Murphy, Pharm.D. a,c , Sally Reel, Ph.D., R.N., F.N.P., F.A.A.N. d , Daniel C. Malone, Ph.D., R.Ph. a,c a Department of Pharmacy Practice and Science, The University of Arizona College of Pharmacy, 1295 N. Martin Ave., P.O. Box 210202, Tucson, AZ 85721, USA b Evaluation Group for Analysis of Data, Departments of Psychology and Pharmacoeconomics, The University of Arizona, Tucson, AZ, USA c The Center for Health Outcomes and PharmacoEconomic Research, The University of Arizona College of Pharmacy, Tucson, AZ, USA d The University of Arizona College of Nursing, Tucson, AZ, USA Abstract Background: It is essential that current and future health professionals be able to evaluate for possible clinically significant drug-drug interactions (DDIs) and when detected, determine appropriate management strategies to prevent patient harm. Objective: Assess the validity of a DDI knowledge assessment instrument in a health professional student population. Methods: This study recruited health professional students (medical, nurse practitioner, and pharmacy) beginning experiential training at the University of Arizona. Students were given a knowledge assessment instrument that included 15 medication pairings selected on the basis of clinical importance and were asked to select the most appropriate DDI management strategy for each pair by selecting ‘‘avoid combination,’’ ‘‘usually avoid combination,’’ ‘‘take precautions,’’ or ‘‘no special precautions.’’ Data were analyzed in 2 ways because of the subjective nature of classifying DDIs into specific management categories. In the first analysis, respondents were given credit for a correct item only if they selected the management strategy deemed appropriate (management strategy analysis). In another analysis, students were given credit for an item only if they correctly identified specific DDIs (DDI recognition analysis). Rasch analysis was used to assess the validity of the knowledge instrument. Funding/Support: This project was funded under grant number U18 HS017001-01 (PI: R. Woosley) from the Agency for Healthcare Research and Quality (AHRQ), U.S. Department of Health and Human Services. The opin- ions expressed in this document are those of the authors and do not reflect the official position of AHRQ or the U.S. Department of Health and Human Services. * Corresponding author. Tel.: þ1 520 235 5529; fax: þ1 520 626 7355. E-mail address: warholak@pharmacy.arizona.edu (T.L. Warholak). 1551-7411/10/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.sapharm.2010.01.001 RSAP219_proof  9 April 2010  12:23 pm ARTICLE IN PRESS Research in Social and Administrative Pharmacy j (2010) j–j Available online at www.sciencedirect.com