Accuracy of the diagnoses of spondylarthritides in veterans affairs medical center databases

Objective. To study the accuracy of diagnoses of spondylarthritides in computerized databases at the Minneapolis Veterans Affairs Medical Center. Methods. Medical records were available and reviewed for a random sample of 184 patients from a cohort of 737 patients seen at the rheumatology clinic between January 1, 2001 and July 31, 2002. We compared 4 database definitions with the medical record gold standard of rheumatologists' diagnosis of ankylosing spondylitis (AS), psoriatic arthritis (PsA), or reactive arthritis (ReA): presence of 1) ≥1 or 2) ≥2 International Classification of Diseases, Ninth Revision (ICD-9) diagnostic codes for diagnoses of AS (720.0), PsA (696.0), and ReA (099.3, 711.11-711.19), and presence of 3) ≥1 or 4) ≥2 ICD-9 codes and prescription of a disease-modifying antirheumatic drug (DMARD). Accuracy was assessed by sensitivity, specificity, positive predictive values (PPVs) and negative predictive values (NPVs), kappa statistic, and receiver operator characteristic (ROC) curve area. Results. Of 184 patients, 11 (6%) had AS, 17 (9%) had PsA, and 7 (4%) had ReA as per the gold standard. ICD-9 codes for AS, PsA, and ReA were very specific (98-100%) with excellent NPV (99-100%) and PPV (83-100%), good to excellent sensitivity (57-100%), almost perfect kappa agreement (0.72-1), and high ROC curve area (0.79-1). Addition of presence of DMARD prescription to ICD-9 codes of AS and PsA decreased sensitivity to 27-65% without improving the specificity (which was already high at 99-100%). Conclusion. The ICD-9 codes for AS, PsA, and ReA in databases are accurate. ICD-9 codes may be used to identify cohorts of patients with spondylarthritides.