Neutropenia is common in patients with human immunodeficiency virus (HIV) disease. However, the degree of risk for serious bacterial infections associated with various levels of neutropenia in patients with HIV disease is not well defined.
A retrospective analysis of databases containing demographic information for patients attending the San Francisco General Hospital HIV outpatient clinic, test results reported by the hospital's clinical laboratory, and the San Francisco General Hospital inpatient International Classification of Diseases, Ninth Revision (ICD-9) hospital discharge diagnosis codes from October 1, 1992, through November 30, 1993. Risk window time periods were defined, encompassing dates that consecutive absolute neutrophil counts (ANCs) occurred in a single ANC stratum. One risk window at the lowest ANC stratum for each patient was analyzed for hospitalizations with ICD-9 codes indicating bacterial infections. A 5% random sample of medical records was reviewed for end point validation.
Codes from ICD-9 had 98% and 96% positive and negative predictive values, respectively, for meeting National Institute of Allergy and Infectious Diseases Division of AIDS [acquired immunodeficiency syndrome] clinical trial end point definitions for bacterial infections. Among 2047 evaluable patients, a significant increase in the incidence of hospitalization for serious bacterial infections was observed for those in the ANC strata of 500 to 749×106/L and below. The 95% confidence intervals for the incidence of hospitalization associated with each ANC stratum below 500×106/L did not overlap with that for any stratum of 750×106/L or higher (22-117 vs 0.4-19 patient hospitalizations per 10 000 days at risk, respectively). A multivariate analysis revealed only the severity and duration of neutropenia and black race to be significant end point predictors.
Among 2047 patients with HIV disease, significantly higher risks of hospitalization for bacterial infections were associated with ANCs lower than 750×106/L, especially for ANCs lower than 500×106/L.Arch Intern Med. 1997;157:1825-1831