Predictors of survival and eradication of Mycobacterium avium complex bacteremia (MAC) in AIDS patients in the Canadian Randomized MAC Treatment Trial

Objective: To assess the importance of baseline characteristics including m edical history, indicators of current disease status, therapeutic drug use, in vitro drug susceptibility, immune status and mycobacterial load on bact eriologic response and survival in HIV-positive patients with Mycobacterium avium complex (MAC) bacteremia. Design: An observational substudy of an open-label randomized controlled tr ial of two alternative therapeutic regimens for MAC. Setting: Twenty-four hospital-based HIV clinics in 16 Canadian cities. Main outcome measures: The main outcome measures were survival and bacterio logic response, defined by consecutive negative blood cultures for MAC at l east 2 weeks apart within 16 weeks of study entry. Results: Prior AIDS diagnosis, low Karnofsky score, active unstable AIDS-re lated conditions, absence of antiretroviral therapy and absence of Pneumocy stis carinii pneumonia prophylaxis were associated with shorter survival by univariate regression using the proportional hazards model. On multivariat e analysis, antiretroviral therapy was not an independent predictor of mort ality, and previous rifabutin prophylaxis was independently associated with poor survival outcomes, a result consistent across study treatment. Using a logistic regression model, baseline quantitative mycobacterial load [rela tive odds of clearing, 1.97 for a decrease of 1 log(10) colony forming coun t; 95% confidence interval (CI), 1.36-2.87; P < 0.001] and Karnofsky score were the only statistically significant univariate predictors of clearance, although previous prophylaxis with rifabutin was also a significant predic tor in a multivariate model (relative adds of clearing, 0.39; 95% CI, 0.17- 0.88; P < 0.05). Conclusions: This study indicates that although the level of MAC bacteremia is an important predictor of clearance, it is not associated with survival . (C) 1999 Lippincott Williams & Wilkins.