Original Investigation 

Infectious Diseases

Blastomycosis, Histoplasmosis, and Coccidioidomycosis in Outpatient Community-Acquired Pneumonia

Kaitlin Benedict, George R. Thompson III, Neil M. Ampel, et al

JAMA Netw Open 2026;9;(1):e2553965. doi:10.1001/jamanetworkopen.2025.53965

Key Points

Question  What proportion of adult outpatients with unspecified community-acquired pneumonia (CAP) underwent diagnostic testing for blastomycosis, coccidioidomycosis, or histoplasmosis, and what proportion tested positive for those diseases?

Findings  In this cohort study of health insurance claims data, among 573 994 patients with unspecified CAP, 5% underwent fungal diagnostic testing, after a median of 3 health care visits. Among tested patients, 3% received a blastomycosis, coccidioidomycosis, or histoplasmosis diagnosis code.

Meaning  These low testing rates highlight the potential for missed diagnoses of blastomycosis, coccidioidomycosis, and histoplasmosis; increased testing could lead to decreased health care utilization and inappropriate antibiotic use, and improve patient outcomes.

Abstract

Importance  Laboratory testing is necessary to distinguish blastomycosis, coccidioidomycosis, or histoplasmosis from other causes of community-acquired pneumonia (CAP). Robust data about testing for and diagnosis of these fungal diseases among patients with CAP throughout the US are lacking.

Objective  To examine proportions and characteristics of (1) adult outpatients with CAP who underwent diagnostic testing for blastomycosis, coccidioidomycosis, or histoplasmosis; and (2) tested patients who received diagnoses of these diseases.

Design, Setting, and Participants  This retrospective cohort study used 2017 to 2023 commercial health insurance claims data from the Merative MarketScan Commercial/Medicare Database. Adult outpatients with diagnosis codes for unspecified CAP were included.

Main Outcomes and Measures  The primary outcome was the proportion of patients who underwent fungal diagnostic testing. The secondary outcomes were the proportions of tested patients who received diagnoses of blastomycosis, coccidioidomycosis, or histoplasmosis. Multivariable logistic regression models were used to estimate adjusted odds ratios (aORs) for characteristics independently associated with receiving a diagnosis of coccidioidomycosis or histoplasmosis.

Results  Among 573 994 patients (318 152 female [55%]; median [IQR] age, 54 [41-63] years) with unspecified CAP, 25 822 (5%) underwent fungal diagnostic testing, which occurred a median (IQR) of 3 (1-6) health care visits after the initial CAP diagnosis. Among tested patients, 755 (3%) received a blastomycosis, coccidioidomycosis, or histoplasmosis diagnosis code. Rash (aOR, 3.24; 95% CI, 2.27-4.63), lymphadenopathy (aOR, 1.74; 95% CI, 1.15-2.63), myalgia (aOR, 1.66; 95% CI, 1.11-2.49), chest pain (aOR, 1.65; 95% CI, 1.35-2.02), and receipt of antibiotics from multiple classes (aOR, 1.40; 95% CI, 1.17-1.67) were independently associated with increased odds of receiving a coccidioidomycosis diagnosis. Autoimmune inflammatory disease (aOR, 3.00; 95% CI, 1.72-5.21), chest pain (aOR, 1.84; 95% CI, 1.20-2.82), and abnormal weight loss (aOR, 5.15; 95% CI, 2.71-9.79) were associated with increased odds of receiving a histoplasmosis diagnosis.

Conclusions and Relevance  In this cohort study of patients with unspecified CAP, testing rates for blastomycosis, coccidioidomycosis, and histoplasmosis were low in many locations. Increased awareness of these fungal infections may help increase timely testing for fungal diseases among patients with CAP, decrease health care utilization and inappropriate antibiotic use, and improve patient outcomes.