Abstract
Background/Aims: Highly active antiretroviral therapy (HAART) successfully treats patients with HIV. However, many patients do not achieve complete suppression. Perhaps the most important reason for treatment failure is infection with antiretroviral drug-resistant variants, which threatens to increase treatment cost as well as limit HAART’s clinical effectiveness. This study examines the resource utilization and cost implications of multi-drug resistance using the HIV+ population of Kaiser Permanente Northern California (KPNC).
Methods: Retrospective cohort analysis of all HIV+ patients in KPNC between January 2000 and June 2005 (total study period). Continuous active membership of 12 months and minimum 12 months of continuous HAART. Cases defined as HIV+ patients on third or later HAART regimen; controls defined as HIV+ patients on first or second HAART regimen. Regimen switch defined as combination change of two or more additions or subtractions of antiretroviral therapy (ART) drugs to or from an existing HAART regimen. Costs include outpatient, inpatient, and pharmacy categories.
Results: All results are for 2004 only (291 cases, 1,676 controls); costs reported in person-years. Mean total pharmacy costs were $17,668 for cases vs $12,417 for controls (P<0.04). Of mean pharmacy costs for cases, 85% were ART-based (controls=90%). Mean number of 2004 fills for both ART and non-ART drugs were higher for cases (20 vs 15 for ART; 21 vs 15 for non-ART). Mean total outpatient costs were $3,275 for cases vs $2,238 for controls (P<0.06). Mean ER visits and mean primary care visits, but not specialty care visits, were both higher for cases than for controls (P<0.03). Mean inpatient costs were $3,803 for cases vs $1,738 for controls. Mean number of stays was higher for cases than for controls (0.29 vs 0.16; P<0.05), but length of stay did not differ between groups.
Conclusions: In 2004, patients with HIV on at least their third HAART regimen incurred mean pharmacy costs 40% higher than similar patients on first or second regimen. Outpatient and inpatient costs also appear higher among cases, but not strikingly so. Overall cost differentials between cases and controls may be underestimates, as laboratory, radiology, and home health have not yet been added. These cost categories may well widen the cost differences between HIV+ patients who have been forced to switch HAART regimens more than once relative to those who have not.
- Received September 11, 2008.
