Risk factors for severe disease due to Toxoplasma gondii in HIV-positive patients

The objective of this study was to assess the risk of toxoplasmosis in HIV-positive subjects as a basis for primary prophylaxis. A retrospective chart review of 400 consecutive patients was carried out and clinical and laboratory markers at first presentation and follow-up data on the occurrence of toxoplasmosis were recorded. Independent variables were identified, laboratory parameters were stratified, and estimates for the risk of toxoplasmosis and the impact of different variables on its occurrence were made using conventional statistical methods. An increased risk of toxoplasmosis was strongly associated with a positive Toxoplasma gondii IgG EIA in conjunction with a CD4+ cell cont below 0.15/nl (the estimated risk of toxoplasmosis was 20% and 35% after 12 and 24 months, respectively) or a history of one or more opportunistic infections (the estimated risk was 12% and 30% after 12 and 24 months, respectively). Toxoplasma gondii-seropositive patients with CD4+ cell counts below 0.15/nl and those with antecedent opportunistic infections are most likely to develop toxoplasmosis and thus might benefit from primary prophylaxis. The risk of disease probably outweighs the risk of medication in these subjects. Prospective clinical trials are needed to define the optimal choice of drugs.