How is histoplasmosis diagnosed?
Definitive diagnosis of histoplasmosis can be complicated, especially if the patient gives no history of exposure to areas contaminated with H. capsulatum. Many bacterial and fungal infections can produce clinical findings that are found with H. capsulatum infections (for example, granulomatous nodules found in sarcoidosis and tuberculosis, or lung infiltrates seen on X-ray in coccidiodomycosis, blastomycosis, aspergillosis, and other lung infections). In fact, before 1932, many patients with chronic pulmonary histoplasmosis were diagnosed as having tuberculosis. Differentiating histoplasmosis from other lung infections can still be a diagnostic challenge for clinicians. Cultures of blood, sputum, or tissue biopsy samples can be cultured on media that supports H. capsulatum growth. If H. capsulatum is cultured, the diagnosis is confirmed. However, at best, cultures are positive in only about 60% of patients with chronic pulmonary infections and are positive in only about 15% of acute c
