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

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.

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.

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.

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.

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.

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.