The value of direct fluorescent antibody (DFA) testing for the detection of Pneumocystis Carinii In cytological specimens

A direct fluorescent antibody (DFA) method was compared with methenamine silver staining (MSS) for the detection of Pneumocystis carinii in 384 cytological specimens. DFA testing was more sensitive than the MSS, with P. carinii detected in 31 specimens with DFA and 24 with the MSS. Results of the two methods disagreed in 17 specimens, all of which were sputa. Twelve sputum specimens were DFA positive/MSS negative and five were MSS positive/DFA negative. It is concluded that the DFA technique, although relatively expensive, is simple to perform and offers superior sensitivity to the MSS. However, in sputum specimens the combined use of DFA and MSS leads to optimal sensitivity for the detection of P. carinii.</p