The recognition of Pneumocystis carinii in routine Papanicolaou-stained smears.

Using definite criteria it is possible to accurately evaluate routine Papanicolaou-stained cytologic smears for the presence or absence of Pneumocystis carinii. Strict attention must be paid to the cellular environment and the background material intimately associated with the cells. In 133 cytology specimens evaluated from proximal and deep bronchial washings and brushings, 71 were considered positive for P. carinii and 62 were called negative. Ten of the latter were either unsatisfactory or equivocal. The 71 positives correlated in every instance with parallel Grocott methenamine silver-stained transbronchial biopsies or brushings. Fifty-one of the 52 satisfactory cytologic negatives also correlated with the biopsy and brushing findings. There was a single false negative. This high degree of correlation indicates that the Papanicolaou-stained specimen can be a valuable tool in the early diagnosis of pneumocystosis.