AN EVALUATION OF 4 METHODS FOR THE DETECTION OF PNEUMOCYSTIS-CARINII IN CLINICAL SPECIMENS

We undertook a prospective evaluation of 4 methods for the detection o f Pneumocystis carinii in clinical specimens and compared an indirect immunofluorescence assay (IFA) (Diagnostics Pasteur), and a fluorescen t whitening agent (FWA) (Blankophor BA 267%, Bayer, Australia) with ou r standard methenamine silver (MeAg) and toluidine blue O (TB) stains. Two hundred and two specimens were received from 162 patients (133 HI V infected, 19 heart or heart-lung transplant recipients, and 10 ''mis cellaneous''). The specimens consisted of 132 induced sputa, 56 bronch oalveolar lavage specimens, 10 fine needle aspiration lung biopsies, e nd 4 pleural fluid specimens P. carinii was detected in 44 (22%) of th e specimens. The sensitivities for the detection of P. carinii pneumon ia were IFA: 92% (95% Cl, 83-100%), FWA: 57% (95% Cl, 41-73%), MeAg: 5 4% (95% Cl, 38-70%), and TB: 49% (95% Cl, 33-65%). Discordant results were greatest in specimens from patients who were receiving specific a nti-P. carinii prophylaxis, or wile had received treatment for several days prior to sampling. IFA was the most sensitive test and relativel y easy to perform. IFA was also the most expensive test. We found the FWA method a useful screening test as it is cheap and quick to perform . However, it is less sensitive than IFA, which should be performed on the negative specimens. With the increasing use of specific anti-P. c arinii prophylaxis in HIV-infected patients,methods more specific and sensitive than MeAg and TB stains are required. We have found IFA to i mprove significantly the rate of detection of P. carinii in this patie nt group.