Background
Accurate and timely methods for the diagnosis of histoplasmosis in resource limited countries are lacking. Histoplasma antigen detection by enzyme immunoassay (EIA) is widely used in the US but not in resource limited countries, leading to missed or delayed diagnoses and poor outcomes. Lateral flow assays (LFA) can be used in this setting.
Methods
Frozen urine specimens were submitted to MiraVista diagnostics for antigen testing from three medical centers in endemic areas of the US. They were blinded and tested for the MVista Histoplasma LFA. Patients were classified as controls or cases of histoplasmosis. Cases were divided into proven or probable, pulmonary or disseminated, immunocompetent or immunosuppressed, and mild, moderate, or severe.
Results
352 subjects were enrolled, including 66 cases (44 proven, 22 probable) and 286 controls. Most of the cases were immunocompromised (71%),46 had disseminated and 20 had pulmonary histoplasmosis. Four were mild, 42 moderate, and 20 severe. LFA and EIA were highly concordant (kappa 0.84). Sensitivity and specificity of the LFA were 78.8% and 99.3% respectively. LFA sensitivity was higher in proven cases (93.2%), patient with disseminated (91.3%), moderate (78.6%) and severe disease (80%), and those with galactomannan levels > 1.8 ng/mL (97.8%). Specificity was 99.3% in proven cases, 99.3% in patient with moderate/severe disease, and 96.8% in those with galactomannan levels > 1.8 ng/mL. Cross reactivity was noted with other endemic mycoses.
Conclusion
The MVista Histoplasma LFA meets the need for accurate rapid diagnosis of histoplasmosis in resource limited countries, especially in patient with high disease burden, potentially reducing morbidity and mortality.