Coccidioidomycosis (CM) is common and important within endemic regions, requiring specific testing for diagnosis. Long delays in diagnosis have been ascribed to ambulatory clinicians. However, how their testing practices have impacted patient care has not been systematically unexplored.

We analyzed practice patterns for CM diagnoses over 3 years within a large Arizona healthcare system, including diagnosis location, patient characteristics, and care-seeking patterns associated with missed diagnosis.

For 2043 CM diagnoses, 72.9% were made during hospital admission, 21.7% in ambulatory clinics, 3.2% in emergency units, and only 0.5% in urgent care units. A 40.6% subgroup of hospitalized patients required neither intensive care unit or hospital-requiring procedures, had a median length of stay of only 3 days, but still incurred both substantial costs ($27.0 million) and unnecessary antibiotic administrations. Prior to hospital diagnosis (median of 32 days), 45.1% of patients had 1 or more visits with symptoms consistent with CM. During those visits, 71.3% were not tested for CM. Diagnoses were delayed a median of 27 days.

Lack of testing for CM in ambulatory care settings within a region endemic for CM resulted in a large number of hospital admissions, attendant costs, and unneeded antibacterial drug use, much of which would otherwise be unnecessary. Improving this practice is challenging since many clinicians did not train where CM is common, resulting in significant inertia to change. Determining the best way to retrain clinicians to diagnose CM earlier is an opportunity to explore which strategies might be the most effective.