Fluorescence of Pneumocystis carinii in Papanicolaou smears.

Pneumocystis carinii organisms can be identified in routine cytologic smears stained by the Papanicolaou method and viewed under ultraviolet light in a fluorescence microscope. The organisms can be identified easily in thin, well-preserved cytologic smears. No false-positive results were obtained when 55 Papanicolaou smears of bronchial washings were observed by this method. Twenty-three of these smears were from patients with Pneumocystic carinii pneumonia in whom the acquired immunodeficiency syndrome (AIDS) had been well documented with Gomori's methenamine silver stain. With this method no additional special stains are required, no time delay for special stains is involved, and no additional material for the preparation of extra smears for special stains is needed. An additional advantage is the possibility of the retrospective analysis of smears already stained by the Papanicolaou method.