Comparison of Papanicolaou's stain with the Gomori methenamine silver (GMS) stain for the cytodiagnosis of Pneumocystis carinii in bronchoalveolar lavage (BAL) fluid.

The cytodiagnosis of Pneumocystis carinii (PC) in bronchoalveolar lavage (BAL) fluids has traditionally required a special stain such as Gomori's methenamine silver (GMS) stain. Recent reports indicate that identification of foamy alveolar casts (FACs) with Papanicolaou's (Pap) stain may provide a sensitive and less complicated way of making the diagnosis. To confirm these observations, results on a series of 318 BALs were reviewed. PC was identified on 65 (20%) specimens from 54 patients. Pap stains and GMS stains were positive on 56 (86%) of these BALs. Pap stains were positive on seven (11%) specimens that had negative GMS stains. PC was later confirmed on these specimens by other methods. Only two (3%) BALs had positive GMS stains and negative Pap stains. The results of this study confirm other reports that show that PC can be sensitively diagnosed with the Pap stain. The authors suggest that routine special stains for PC are unnecessary on BALs.