Analysis of life-long strategies to prevent Pneumocystis carinii pneumonia in patients with variable HIV progression rates.

Abstract

To compare strategies for life-long prophylaxis of Pneumocystis carinii pneumonia (PCP) in a group of AIDS patients with a wide range of disease progression rates. Markov decision models. Prophylaxis strategies using high and low doses of trimethoprim-sulfamethoxazole (TS), dapsone, and/or aerosolized pentamidine in sequence, were compared. Efficacy and toxicity rates for prophylaxis regimens were taken from a meta-analysis of pertinent randomized controlled trials. Outcomes measured included lifetime episodes of PCP and drug toxicity per 100 patients treated, average life expectancy, and cost. For patients with an expected survival of 3 years after commencement of prophylaxis, the use of standard or low dose TS as the first choice agent was comparable, and both were superior to the other strategies for preventing PCP (between nine and 26 fewer episodes of PCP per 100 patients treated) though they were more toxic (11-44 more episodes of toxicity per 100 patients treated). Life expectancy was similar for all of the treatment strategies. With slower rates of disease progression (expected survival > 3.8 years), as seen with current antiretroviral regimens, the use of low dose TS as the first choice agent dominated the use of standard dose TS; when the expected survival time was 7 years, initial use of low dose TS led to 2.8 fewer episodes of PCP per 100 patients treated, 32 fewer episodes of toxicity per 100 patients treated, and US$1381 per patient lower cost, compared with prophylaxis with standard dose TS. For patients with AIDS and expected survival > 3.8 years, low dose TS is better than standard dose TS as the first choice agent for preventing PCP. As patients with AIDS live longer, the routine use of low dose TS will be more than adequate for patients at risk for PCP.