Evaluation of calcofluor white stain for detection of Pneumocystis carinii

A rapid calcofluor white (CFW) stain for detecting Pneumocystis carinii was evaluated prospectively. Eighty-nine bronchoalveolar lavage (BAL) specimens, 21 open-lung biopsy (OLB) tissues, 2 induced sputums, 1 expectorated sputum, 2 tracheal secretions, and 1 bronchial secretion from 102 patients were examined for P. carinii cysts by both the CFW stain and a modified methenamine silver (MS) stain. Twenty episodes of P. carinii pneumonia were detected: 19 of these episodes were detected by CFW stain, and 16 of those episodes were detected by MS stain. Discrepancies between the two staining methods were resolved by review of the clinical histories and, in one case, by testing an OLB specimen. Neither staining procedure gave false-positive results with any specimen. More cysts were detected in CFW-stained specimens than in MS-stained specimens (p = 0.05). CFW stain is a simple, rapid, and inexpensive method for detecting P. carinii in clinical specimens and is at least as sensitive as MS stain.