Correlation of Pneumocystis carinii cyst density with mortality in patients with acquired immunodeficiency syndrome and pneumocystis pneumonia.

Fifteen percent to 20% of patients with the acquired immunodeficiency syndrome and pneumocystis pneumonia do poorly despite early intervention. It is not known what distinguishes those who die, despite early intervention and aggressive therapy, from those who readily respond to therapy. We used image analysis to determine the relative abundance of cysts within aggregates of Pneumocystis carinii found in induced sputa (21 patients) and bronchoalveolar lavage fluid (14 patients) from 35 patients with pneumocystis pneumonia. We calculated a cyst density (number of cysts per area of aggregate) for each aggregate and a mean cyst density for all of the aggregates on the smear. Six patients died within 2 weeks of diagnosis; four of these six patients who had autopsies all had residual P carinii. The mean cyst density for those who died was 9.7 +/- 3.9 (range, 5 to 15 x 10(-3)). The 29 patients who survived beyond 2 weeks had a mean cyst density of 18.4 +/- 8.7 (range, 5 to 35 x 10(-3); P = .01). Mean cyst density was not influenced by the number of aggregates present in the smear, the variation in cyst density among aggregates in a smear, or the episode of pneumocystis pneumonia. Cyst density determinations alone should not be used to predict outcome for individuals with P carinii pneumonia until further study is completed. Nevertheless, the current study suggests that a low cyst density specimen, which may indirectly indicate a greater proportion of trophozoites compared with a high cyst density specimen, may be associated with an unfavorable outcome in acquired immunodeficiency syndrome-associated pneumocystis pneumonia.