Changes in the incidence of severe thrombocytopenia and its predisposing conditions in HIV-infected patients since the introduction of highly active antiretroviral therapy

BACKGROUND:: Severe thrombocytopenia (platelets <50x10/L) is relatively frequent during HIV infection and is associated with bleeding risk and disease progression. We investigated the changes in the incidence of severe thrombocytopenia and its predisposing conditions in a cohort of HIV-positive subjects.METHODS:: The incidence and predictors of platelet counts <50x10/L were investigated in all patients enrolled at our Institution between 1985 and 2012. Three different periods were considered on the basis of the available antiretroviral regimens: P1 (1985-1989), P2 (1990-1996) and P3 (1997-2012). Incidence rates were assessed using Poisson regression models, and the predictors by means of Cox regression.RESULTS:: The study involved 5,137 patients with platelet counts >50x10/L at enrolment. Severe thrombocytopenia occurred in 597 subjects, and its incidence decreased overtime. The incidence decreased in patients with opportunistic diseases and malignancies, but increased in patients with chronic liver disease; thrombocytopenia unrelated to any cause other than HIV infection remained stable. Multivariate analysis showed that injected drug use, a diagnosis of AIDS, low CD4+ cell counts, increased serum alanine aminotransferase levels and an earlier year of enrolment were predictors of an increased risk of severe thrombocytopenia, whereas the use of highly active antiretroviral therapy (HAART) was associated with a reduced risk.CONCLUSIONS:: A considerable reduction in the incidence of severe thrombocytopenia after the introduction of HAART was found, probably due to its ability to limit bone marrow damage induced by uncontrolled HIV replication and opportunistic infections. On the contrary, HAART may have a reduced impact on thrombocytopenia related to chronic liver disease.