Abstract
RATIONALE: Immunocompromised patients are at high risk for developing severe sepsis. Currently, there are no validated strategies for identifying this group of patients in large administrative databases. OBJECTIVES: We set out to define and validate a method that could be used to identify immunocompromised patients with severe sepsis in administrative databases. METHODS: Patients were categorized as immunocompromised based on the presence of International Classification of Diseases, 9th revision discharge diagnosis codes and medication data. We validated this strategy by comparing the discriminatory ability of the search algorithm to that of manual chart review. MEASUREMENTS AND MAIN RESULTS: We identified 4,438 patients at a single academic center with severe sepsis using a definition applied to administrative data described by Angus and colleagues. There were 1,185 (26.7%) who were categorized as immunocompromised based on our novel administrative data search strategy. Compared with identification by medical record review, the new administrative data search strategy had positive and negative predictive values of 94.4% (95% confidence interval [CI], 88.8-97.7%) and 94.3% (95% CI, 91.0-96.6%). The sensitivity and specificity were 87.4% (95% CI, 80.6-92.5%) and 97.6% (95% CI, 95.0-99.9%). CONCLUSIONS: Patients who are immunosuppressed are a large subgroup of those with severe sepsis. Following its validation as a search strategy using other large databases, and its adaptation for International Classification of Diseases, 10th revision, this novel method may allow researchers to account for a patient's immune state when examining outcomes.