Real-world Evaluation of Histoplasmosis Diagnosis and Treatment in Patients From a Michigan Health System.

Background: Despite classification as the most common endemic mycosis in the United States, few data exist supporting the optimal care of patients with histoplasmosis, making diagnosis and treatment challenging. This study aimed to describe patients with histoplasmosis across a Michigan health system. Methods: A retrospective, multicenter cohort study of patients diagnosed with histoplasmosis between January 2020 and April 2023. The primary objective was to describe patients diagnosed with histoplasmosis, methods of diagnosis, and treatment they received. Patient outcomes, including mortality with treatment, and 6-month relapse of disease, were also evaluated. Results: A total of 88 patients were included in the study, and most received care from an infectious diseases provider (86.4%). Tissue histopathology was the most common diagnostic method (59%). Treatment was initiated in 58 patients (66%); 17 (29.3) had disseminated disease. Five (8.6%) patients died within 6 months. Itraconazole was the agent most prescribed for definitive therapy (81%) followed by posaconazole (17%). Median treatment duration was 24 weeks. Adverse events occurred in more than one quarter of patients receiving triazoles. Loading doses were absent in 35% of itraconazole prescriptions; therapeutic drug monitoring was absent in 19.2%. No patients experienced a relapse of disease within 6 months of therapy completion. Conclusions: In a cohort of patients with histoplasmosis from Michigan, variation in diagnostic testing and treatment was observed. Most patients were diagnosed by positive tissue histopathology and itraconazole was the most frequently prescribed antifungal followed by posaconazole. Opportunities for more sensitive diagnostic testing and improved antifungal dose optimization and monitoring were identified.