Cost-Effectiveness of Primary Prophylaxis of AIDS Associated Cryptococcosis in Cambodia

Background: Cryptococcal infection is a frequent cause of mortality in Cambodian HIV-infected patients with CD4+ count <= 100 cells/mu l. This study assessed the cost-effectiveness of three strategies for cryptococcosis prevention in HIV-infected patients. Methods: A Markov decision tree was used to compare the following strategies at the time of HIV diagnosis: no intervention, one time systematic serum cryptococcal antigen (CRAG) screening and treatment of positive patients, and systematic primary prophylaxis with fluconazole. The trajectory of a hypothetical cohort of HIV-infected patients with CD4+ count <= 100 cells/mu l initiating care was simulated over a 1-year period (cotrimoxazole initiation at enrollment; antiretroviral therapy within 3 months). Natural history and cost data (US$ 2009) were from Cambodia. Efficacy data were from international literature. Results: In a population in which 81% of patients had a CD4+ count <= 50 cells/mu l and 19% a CD4+ count between 51-100 cells/mu l, the proportion alive 1 year after enrolment was 61% (cost $ 472) with no intervention, 70% (cost $ 483) with screening, and 72% (cost $ 492) with prophylaxis. After one year of follow-up, the cost-effectiveness of screening vs. no intervention was US$ 180/life year gained (LYG). The cost-effectiveness of prophylaxis vs. screening was $ 511/LYG. The cost-effectiveness of prophylaxis vs. screening was estimated at $1538/LYG if the proportion of patients with CD4+ count <= 50 cells/mu l decreased by 75%. Conclusion: In a high endemic area of cryptococcosis and HIV infection, serum CRAG screening and prophylaxis are two cost effective strategies to prevent AIDS associated cryptococcosis in patients with CD4+ count <= 100 cells/mu l, at a short-term horizon, screening being more cost-effective but less effective than prophylaxis. Systematic primary prophylaxis may be preferred in patients with CD4+ below 50 cells/mu l while systematic serum CRAG screening for early targeted treatment may be preferred in patients with CD4+ between 51-100 cells/mu l.