Usefulness of Serum as a Non-Invasive Sample for the Detection of Histoplasma capsulatum Infections: Comparative Analysis of Different Diagnostic Techniques

Diagnosis of histoplasmosis is challenging. A rapid, sensitive, and specific method is essential. Serum is a non-invasive and easy sample to obtain in any hospital. The diagnostic accuracy of different techniques that use serum has been evaluated. Forty one serum samples from patients with proven or probable histoplasmosis were analyzed. Different techniques based on the detection of antibodies, (ID Fungal Antibody System), antigens (Histoplasma GM EIA and Platelia TM Aspergillus Ag) and DNA (“in house “real time PCR (RT-PCR) have been tested. Additionally, 36 sera samples were selected for the quantification of cytokines and biomarkers related to histoplasmosis. The sensitivity of the Histoplasma GM EIA kit was 94% in patients with disseminated infection and HIV as underlying disease, in immunocompetent (IC) patients it was 66%. The detection of Histoplasma spp. with the ID Fungal Antibody System was positive in 84% of IC and in 68% of HIV patients. The Platelia-Asp kit had a low performance in both groups of patients (38% HIV and 21% non-HIV) and, finally, RT-PCR was better in immunosuppressed patients (47% HIV vs. 26% non-HIV). Combination of diagnostic tecniques increased the detection Histoplasma infection in inmunosupressed patients. Overall, patient groups infected with H. capsulatum (Hc) showed higher IL-8, IL-6, IL-1β, TNF-α, IL-18 median values compared to not Hc infected controls. The effectiveness of diagnostic techniques on serum samples is highly influenced by the patient's clinical presentation and underlying condition. Consequently, a thorough assessment of the patient's clinical presentation and disease phenotype is crucial in selecting the most suitable diagnostic method.