Hospital utilization and costs in a cohort of injection drug users

Background: Many injection drug users (IDUs) seek care at emergency departm ents and some require hospital admission because of late presentation in ti he course of their illness. We determined the predictors of frequent emerg ency department visits and hospital admissions among community-based IDUs a nd estimated the incremental hospital utilization costs incurred by IDUs wi th early HIV infection relative to costs incurred by HIV-negative IDUs. Methods: The Vancouver Injection Drug User Study (VIDUS) is a prospective c ohort study involving IDUs that began in 1996. Our analyses were restricted to the 598 participants who gave informed consent for our study. We used t he participants' responses to the baseline VIDUS questionnaire and, from me dical records at St. Paul's Hospital, Vancouver, we collected detailed info rmation about the frequency of emergency department visits, hospital admiss ions and the primary diagnosis for all visits or hospital stays between May 1, 1996, and Aug. 31, 1999. The incremental difference in hospital utiliza tion costs by HIV status was estimated, based on 105 admissions in a subgro up of 64 participants. Results: A total of 440 (73.6%) of the 598 IDUs made 2763 visits to the eme rgency department at St. Paul's Hospital during the study period. Of these 440, 265 (60.2%) made frequent visits (3 or more). The following factors we re associated with frequent use: HIV-positive status (seroprevalent: adjust ed odds ratio [OR] 1.7, 95% confidence interval [CI] 1.2-2.6; seroconverted during study period: adjusted OR 3.0, 95% Cl 1.6-5.7); more than 4 injecti ons daily (adjusted OR 1.5, 95% CI 1.1-2.1); cocaine use more frequent than use of other drugs (adjusted OR 2.0, 95% CI 1.2-3.6); and unstable housing (adjusted OR 1.5, 95% CI 1.1 -2.2). During the study period 210 of the par ticipants were admitted to hospital 495 times; 118 (56.2%) of them were adm itted frequently (2 or more admissions). The 2 most common reasons for admi ssion were pneumonia (132 admissions among 79 patients) and soft-tissue inf ections (cellulitis and skin abscess) (90 admissions among 59 patients). Th e following factors were independently associated with frequent hospital ad missions: HIV-positive status (seroprevalent: adjusted OR 5.4, 95% CI 3.4-8 .6; seroconverted during study period: adjusted OR 2.9, 95% CI 1.4-6.0); an d female sex (adjusted OR 1.8, 95% CI 1.1-3.1). The incremental hospital ut ilization costs incurred by HIV-positive IDUs relative to the costs incurre d by HIV-negative IDUs were $1752 per year. Interpretation: Hospital utilization was significantly higher among communi ty-based IDUs with early HIV disease than among those who were HIV negative . Much of the hospital use was related to complications of injection drug u se and may be reduced with the establishment of programs that integrate har m reduction strategies with primary care and addiction treatment.