Accuracy of Administrative Data for Identifying Patients With Pneumonia

The goal of this study was to determine the accuracy and the impact of 5 different claims-based pneumonia definitions. Three International Classification of Diseases, Version 9, (ICD-9), and 2 diagnosis-related group (DRG) -based case identification algorithms were compared against an independent, clinical pneumonia reference standard. Among 10748 patients, 272 (2. 5%) had pneumonia verified by the reference standard. The sensitivity of claims-based algorithms ranged from 47. 8% to 66. 2%. The positive predictive values ranged from 72. 6% to 80. 8%. Patient-related variables were not significantly different from the reference standard among the 3 ICD-9-based algorithms. DRG-based algorithms had significantly lower hospital admission rates (57% and 65% vs 73. 2%), lower 30-day mortality (5. 0% and 5. 8% vs 10. 7%), shorter length of stay (3. 9 and 4. 1 days vs 5. 6 days), and lower costs (USD 4543 and USD 5159 vs USD 8585). Claims-based identification algorithms for defining pneumonia in administrative databases are imprecise. ICD-9-based algorithms did not influence patient variables in our population. Identifying pneumonia patients with DRG codes is significantly less precise.