Diagnosis of Pneumocystis carinii pneumonia

Pneumocystis carinii pneumonia occurs at some point in the course of disease in approximately 85 per cent of patients with AIDS. Because of the frequency of P. carinii pneumonia and because it is readily treatable, prompt, accurate, and efficient diagnostic schemes are of extreme importance. The clinical presentation is generally characterized by fever, nonproductive cough, and shortness of breath. Such symptoms in a patient from a recognized HIV transmission category should prompt a diagnostic evaluation to identify P. carinii or other opportunistic infections. A chest radiograph usually provides an objective indication of lung disease. Pulmonary function tests, particularly the DLCO and lung imaging using 67Ga-citrate, are useful screening tests in patients with normal chest films. Examination of sputum induced by inhalation of a mist of hypertonic saline is a very useful means of identifying P. carinii. Bronchoalveolar lavage is nearly 100 per cent sensitive to the presence of P. carinii and should be performed in patients who have a nondiagnostic sputum examination. Transbronchial biopsy increases the overall yield for diagnoses other than P. carinii and should be performed in patients in whom bronchoalveolar lavage does not provide a diagnosis. Because of the effectiveness of sputum examinations and bronchoscopic procedures, open lung biopsy is rarely necessary. Measurements of circulating P. carinii antigen and antibodies are of no help in diagnosis.