Etiologic diagnosis of acute pneumonia in adults: a growing challenge.

For most pneumonia patients, an etiologic diagnosis can be established by proper use of noninvasive methods. Cultures of blood and pleural fluid and serologic titers are the most specific. The clinical history is helpful in distinguishing community- from hospital-acquired pneumonia and in identifying patients who are immunosuppressed or aspiration prone. When noninvasive diagnostic means and initial antibiotic therapy fail, the physician must choose between further empiric treatment and an invasive procedure with its attendant risks. For seriously ill and immunosuppressed patients, the need for an etiologic diagnosis is usually sufficient to justify these risks. The need for invasive diagnostic procedures is likely to increase in the future, necessitating greater knowledge of the relative risks and merits of each procedure on the part of all physicians who treat patients with pneumonia.