Accuracy of veterans administration databases for a diagnosis of rheumatoid arthritis

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Abstract
Objective To determine the accuracy of International Classification of Diseases (ICD) code 714 for rheumatoid arthritis (RA) diagnosis in a Veterans Administration (VA) hospital database and to examine the effects of adding laboratory and pharmacy data to ICD code 714 on accuracy of RA diagnosis. Methods We drew a random sample of patients from all Minneapolis VA rheumatology clinic patients who had at least 1 rheumatology clinic visit between January 2001 and July 2002. Charts of 184 patients were reviewed. The gold standard for RA diagnosis was chart documentation of RA diagnosis by a rheumatologist on ≥2 visits >6 weeks apart. The data definitions of RA diagnosis included presence of ICD code 714 alone or various combinations of ICD code 714, a positive rheumatoid factor (RF), and prescription for a disease-modifying antirheumatic drug (DMARD). Accuracy of data definitions of RA was assessed by calculating sensitivity, specificity, positive and negative predictive values, and area under the receiver operator characteristics curve. Results Diagnosis by ICD code 714 had 100% sensitivity, but specificity was only 55% because of a false-positive rate of 34%. The addition of a positive RF and/or a DMARD prescription to ICD code 714 dramatically improved specificity to 83–97% and positive predictive value to 81–97%; however, sensitivity decreased to 76–88%. Diagnosis by ICD 714 alone had the highest negative predicative value of 100%. The area under the curve was the greatest when both ICD code 714 and a positive RF were included, and the least when ICD code alone was used. Conclusion ICD code 714 in the VA administrative database is a very sensitive screening tool for identifying patients with RA in the rheumatology clinic population. Addition of the presence of a DMARD prescription and/or a positive RF to selection criteria improves specificity of the diagnosis.