Abstract

Background.Histochemical staining of bone marrow biopsy samples for microorganisms may provide a presumptive diagnosis weeks before culture. Methods.To identify predictors of histochemical positivity, we reviewed 161 bone marrow biopsies from febrile patients with human immunodeficiency virus (HIV) infection. Results.By multivariate analysis, both hematocrit value <30% and white blood cell count <4,000/mm3 predicted biopsy positivity by culture or staining, but only anemia predicted histochemical stain positivity. Of cases with serum lactate dehydrogenase (LDH) levels >600 U/L, histoplasmosis was diagnosed in 31.6% versus 7.8% with lower LDH levels. Among histoplasmosis cases, staining showed fungi in all, with LDH levels >600 U/L versus 44.4% with lower levels. Conclusions.Bone marrow biopsy will most likely provide a rapid diagnosis in patients with anemia. Markedly elevated LDH levels suggest stain positivity for Histoplasma capsulatum. Histopathologic patterns may also guide empiric therapy.