Risk stratification of ambulatory patients suspected of Pneumocystis pneumonia.

To determine whether aspects of clinical history, physical examination, and laboratory studies improve the diagnostic accuracy of the chest roentgenogram in the diagnosis of Pneumocystis carinii pneumonia (PCP), we followed up 302 consecutive patients with respiratory symptoms and risk factors for human immunodeficiency virus. Of the 279 patients (92%) with follow-up information available, 31 (11%) were diagnosed with PCP. Only 68% of patients with PCP had typical chest roentgenograms. Regression analysis identified four independent predictors of PCP: diffuse or perihilar infiltrates, presence of mouth lesions, lactate dehydrogenase level more than 220 U/L, and erythrocyte sedimentation rate 50 mm/h or more. Using these four predictors, patients could be stratified into low-, intermediate-, and high-risk groups for PCP. We suggest that examination of the mouth, chest roentgenogram, lactate dehydrogenase level, and erythrocyte sedimentation rate be part of the evaluation of ambulatory patients with respiratory symptoms at risk for human immunodeficiency virus.