Pneumocystis carinii pneumonia in patients with connective tissue diseases- The role of hospital experience in diagnosis and mortality

Objective. Pneumonia due to Pneumocystis carinii has been increasingly repo rted in patients with connective tissue diseases, but the frequency of this complication is not known. We sought to determine the frequency of P carin ii pneumonia (PCP) in patients with connective tissue diseases, and to dete rmine the role that a hospital's acquired immunodeficiency syndrome (AIDS)- related experience may have in the diagnosis of PCP in these patients. Methods. We used a state hospitalization registry to identify all patients with PCP and either rheumatoid arthritis, systemic lupus erythematosus, Weg ener's granulomatosis, polymyositis, dermatomyositis, polyarteritis nodosa, or scleroderma who had an emergent or urgent hospitalization in California from 1983 to 1994. We compared patient and hospital characteristics betwee n these patients and patients with connective tissue diseases hospitalized with other types of pneumonia. Results. Two hundred twenty-three patients with connective tissue diseases were diagnosed with PCP in the 12-year study period. The frequency of PCP r anged from 89 cases/10,000 hospitalizations/year in patients with Wegener's granulomatosis to 2 cases/10,000 hospitalizations/year in patients with rh eumatoid arthritis. Compared with 5,457 patients with connective tissue dis eases and pneumonia due to other organisms, patients with PCP were more lik ely to be younger, to be male, to have private medical insurance, and to ha ve systemic lupus erythematosus, Wegener's granulomatosis, inflammatory myo pathy, or polyarteritis nodosa rather than rheumatoid arthritis, and were l ess likely to be African American. Hospital size, teaching status, urban/ru ral location, proportion of admissions due to AIDS or PCP and proportion of patients with pneumonia undergoing bronchoscopy were each associated with the likelihood of diagnosis of PCP in univariate analyses, but only the num ber of patients with PCP being treated at a hospital (odds ratio [OR] 1.03 for each additional 10 cases/year, 95% confidence interval [95% CI] 1.01-1. 05) was associated with the likelihood of diagnosis of PCP in multivariate analyses. Patients were also somewhat more likely to be diagnosed with PCP if there had previously been a case of PCP in a patient with a connective t issue disease at the same hospital (OR 1.35, 95% CI 0.98-1.85). In-hospital mortality was 45.7%, and was unrelated to hospital characteristics. Conclusion. PCP is an uncommon, but often fatal, occurrence in patients wit h connective tissue disease. A hospital's Drier experience with patients wi th PCP is associated with the likelihood that this condition is diagnosed i n patients with connective tissue diseases who present with pneumonia, sugg esting that diagnostic suspicion is an important factor in the correct iden tification of affected patients.