Testing for Blastomycosis, Coccidioidomycosis, and Histoplasmosis at a Major Commercial Laboratory, United States, 2019–2024

Abstract

Background Blastomycosis, coccidioidomycosis, and histoplasmosis are environmentally acquired fungal diseases that clinically resemble bacterial and viral community-acquired pneumonia and require laboratory testing for diagnosis. Patients frequently present to primary care and experience diagnostic delays when a fungal etiology is not initially suspected. Current national-level public health surveillance for these diseases is limited and does not include laboratory data, so nationwide testing practices are unknown. Methods We identified laboratory tests for blastomycosis, coccidioidomycosis, and histoplasmosis ordered during March 1, 2019–February 29, 2024 and performed within a major national commercial laboratory system. We analyzed test results, patient and healthcare provider features, reasons for testing, and temporal trends. Results Results included 5,693 Blastomyces complement fixation tests (of those, 12% were positive), 71,858 immunodiffusion tests (0.1% positive), and 1,186 serum enzyme immunoassay (EIA) tests (11% positive); 154,989 Coccidioides EIA IgM results (5% positive) and 154,968 IgG results (8% positive); and 46,346 Histoplasma complement fixation tests (30% positive), 49,062 immunodiffusion tests (1% positive), 35,506 serum EIA (4% positive), and 82,489 urine EIA tests (2% positive). Most histoplasmosis (58%–74%) and blastomycosis (42%–68%) tests were ordered from hospitals, whereas coccidioidomycosis tests were most frequently ordered by primary care providers (40%). A yearly average of 2,727 positive tests were ordered by health care providers in states without public health surveillance for these diseases. Conclusions Blastomycosis, coccidioidomycosis, and histoplasmosis are likely under-detected in primary care settings or by public health surveillance. Increased testing by primary care providers and expanded surveillance are needed to reduce disease burden.