A Critical Review of Diagnostic Methods for Disseminated Histoplasmosis with Special Focus on Resource-Limited Settings

Purpose of Review The diagnosis of disseminated histoplasmosis remains a challenge particularly in developing countries chiefly due to the low number of required skilled personnel and poor accessibility to diagnostic tools. While culture remains the gold standard in the diagnosis of disseminated histoplasmosis, it requires a period of 1 to 6 weeks of incubation to achieve growth, thus delaying the initiation of treatment. Histoplasma antigen detection is an alternative diagnostic method but has not gained routine utility in resource-limited settings probably due to high cost. Molecular techniques have also been shown to have high sensitivity in the diagnosis of disseminated histoplasmosis but they are very expensive and not easily affordable. Besides the above techniques, Histoplasma can also be detected on peripheral blood film but this is not routinely utilized in the diagnosis of disseminated histoplasmosis. The purpose of this review is to demonstrate the use of peripheral blood film or blood smear as a diagnostic tool for disseminated histoplasmosis in resource-limited settings where classical diagnostic methods are not readily available. Recent Findings We highlight fifty-eight case reports of disseminated histoplasmosis diagnosed on peripheral blood film. Of the 58, 53 (91.4%) were confirmed by classical diagnostic methods, 62.3% (33/53) by culture, 56.6% (30/53) by histopathology, 32.1% (17/53) by serology, 13.2% (7/53) by molecular detection and 3.8% (2/53) by cytology. Summary Blood smears should be done in every patient being evaluated for disseminated histoplasmosis. It is yet an important tool for the diagnosis of disseminated histoplasmosis and is affordable. Comparative studies elucidating the performance of peripheral blood film in the diagnosis of disseminated histoplasmosis against a culture standard should be carried out.