Prevalence of histoplasmosis and molecular characterization of Histoplasma in patients with presumptive pulmonary tuberculosis in Calabar, Nigeria.

Abstract Background Several case reports abound in literature about cases of histoplasmosis misdiagnosed as tuberculosis (TB). Nigeria is one of the highest TB burdened countries but data on histoplasmosis in Nigeria are sparse in the literature. The aim of this research was to investigate patients with presumptive pulmonary tuberculosis (TB) in Calabar, Nigeria, for histoplasmosis. Methods This was a descriptive cross-sectional study of 213 participants with presumptive diagnosis of pulmonary TB between April 2020 and March 2021. Urine samples were collected from selected patients for Histoplasma antigen test using enzyme immunoassay assay kits (IMMY, USA), while sputum samples were collected for GeneXpert test for confirmed diagnosis of TB and conventional PCR for the diagnosis of histoplasmosis. Results Of the 213 participants enrolled into the study, ninety-four subjects (44.0%) were confirmed TB patients, 75 (35.0%) were HIV-positive, 41 (19.0%) had advanced HIV disease (AHD), while 138 (37.0%) were HIV-negative. Twenty-seven of the 213 participants were positive for Histoplasma by antigen test and/or PCR, giving an overall prevalence rate of 12.7%. The prevalence of histoplasmosis amongst confirmed TB patients of 7.0% (7/94) was significantly lower than 16.8% (20/119) in unconfirmed TB patients (p = 0.04). Participants on anti-TB therapy also had significantly lower rate of histoplasmosis compared to those not on anti-TB drugs (p = 0.00006). Conclusion Histoplasmosis is not uncommon amongst presumptive TB patients. There should be proper microbiological investigation of patients presenting with symptoms suggestive of TB to exclude cases of histoplasmosis.