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.