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Measuring Diagnoses: ICD Code Accuracy


  • Kimberly J. O'Malley,

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    • Address correspondence to Kimberly J. O'Malley, Ph.D., Pearson Educational Measurement, 2201 Donley Drive, Suite 195, Austin, TX 78758. Karon F. Cook, Ph.D., Associate Director for Research, is with the Parkinson's Disease Research, Education and Clinical Center, Michael E. DeBakey VA Medical Center, Houston, TX. Matt D. Price, M.S., R.H.I.A., Kimberly Raiford Wildes, Dr.P.H., M.A., and Carol M. Ashton, M.D., M.P.H., are with the Houston Center for Quality of Care and Utilization Studies, Houston VA Medical Center, Baylor College of Medicine, Department of Medicine, Section of Health Services Research, Michael E. DeBakey VA Medical Center, Houston, TX. John F. Hurdle, M.D., Ph.D., is with the VA Salt Lake City Health Care System, Salt Lake City, UT.

  • Karon F. Cook,

  • Matt D. Price,

  • Kimberly Raiford Wildes,

  • John F. Hurdle,

  • Carol M. Ashton


Objective. To examine potential sources of errors at each step of the described inpatient International Classification of Diseases (ICD) coding process.

Data Sources/Study Setting. The use of disease codes from the ICD has expanded from classifying morbidity and mortality information for statistical purposes to diverse sets of applications in research, health care policy, and health care finance. By describing a brief history of ICD coding, detailing the process for assigning codes, identifying where errors can be introduced into the process, and reviewing methods for examining code accuracy, we help code users more systematically evaluate code accuracy for their particular applications.

Study Design/Methods. We summarize the inpatient ICD diagnostic coding process from patient admission to diagnostic code assignment. We examine potential sources of errors at each step and offer code users a tool for systematically evaluating code accuracy.

Principle Findings. Main error sources along the “patient trajectory” include amount and quality of information at admission, communication among patients and providers, the clinician's knowledge and experience with the illness, and the clinician's attention to detail. Main error sources along the “paper trail” include variance in the electronic and written records, coder training and experience, facility quality-control efforts, and unintentional and intentional coder errors, such as misspecification, unbundling, and upcoding.

Conclusions. By clearly specifying the code assignment process and heightening their awareness of potential error sources, code users can better evaluate the applicability and limitations of codes for their particular situations. ICD codes can then be used in the most appropriate ways.