Objectives: To study prospectively HIV-positive patients admitted to the hospital because of pneumonia by extensive laboratory tests to determine specific microbiologic diagnoses and to establish the best clinical diagnosis after review of all available data by expert clinicians.
Methods: Patients admitted to one of two hospitals had extensive questionnaires completed and defined diagnostic tests performed on blood, sputum, urine and bronchoalveolar lavage specimens, when available.
Results: A total of 230 patients had a diagnosis of pneumonia verified. A definite or probable etiologic diagnosis was made in 155 (67%) of these patients. Pneumocystis carinii caused 35% of all cases of pneumonia. Twenty-seven percent of cases of pneumonia with a single etiology had a definite or probable bacterial etiology. 'Atypical agents' were distinctly uncommon. Few clinical or laboratory parameters could differentiate specific etiologies.
Conclusions: P. carinii continues to be a common cause of pneumonia in these patients. The rarity of 'atypical agents' could simplify the empiric approach to therapy. Despite the use of extensive testing we did not find a definite etiology in a large number of cases.