Pneumocystis carinii in sputum. Comparable efficacy of screening stains and determination of cyst density.Arch Pathol Lab Med. 1988 Aug; 112(8):816-20.AP
To determine whether accurate quantification of Pneumocystis carinii cysts in sputum is possible using currently available means and to determine the optimal stain for screening sputum for P carinii, we undertook a comparative evaluation of readily available stains: (1) Diff-Quik, a stain that provides tinctorial detail comparable with Giemsa, (2) toluidine blue, and (3) silver methenamine on simultaneously thawed sputum samples containing P carinii. We also studied the Diff-Quik stain in combination with (4) toluidine blue and (5) silver methenamine. The three stains were comparable for screening purposes. Each disclosed similar numbers of P carinii aggregates on similarly prepared slides. Cysts were difficult to recognize on Diff-Quik due to the negatively staining character of the cyst wall with this stain. The cyst-wall stains, toluidine blue and silver methenamine, clearly stained the cyst wall. The combination of a cyst-wall stain with Diff-Quik allowed visualization of cysts, highlighted by the cyst-wall stain, and aggregate area, delineated by the Diff-Quik, allowing expression of number of cysts per aggregate area, a measure termed cyst density.