Thrombocytopenia is common in patients with HIV infection. However, given the number of potential etiologies of low-platelet counts in this patient population, it is often difficult to determine the underlying cause. The immature platelet fraction (IPF) measures the number of reticulated platelets in peripheral blood and can be used to help determine if thrombocytopenia is secondary to low-platelet production or increased platelet turnover. We studied the performance characteristics of the IPF% in 50 inpatients with HIV-related thrombocytopenia and compared the results with 34 inpatients with HIV and normal platelet counts. The mean IPF% in the HIV thrombocytopenic group was 10.2% as compared with 6.8% in the HIV normal platelet count group (P 5 0.001) and 3.1% in historical non-HIV controls (P < 0.001). In multivariate analyses, the presence of ITP, active infection, log CD4 count, platelet count, and diabetes mellitus were significantly associated with a higher IPF%. These findings suggest that increased platelet turnover plays an important role in the pathogenesis of HIV thrombocytopenia. Platelet turnover is also increased in patients with HIV in general, even when overt thrombocytopenia is absent.
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