The Use of Oral Washes to Diagnose Pneumocystis carinii Pneumonia: A Blinded Prospective Study Using a Polymerase Chain Reaction-Based Detection System [Fischer S et al. JID 2001;184:1485] This is a report from the NIH using PCR to detect P. carinii in oral washes and in BAL or induced sputum samples. The study included 175 paired samples including 32 from patients with PCP detected by conventional microscopy of BAL or induced sputum. The results showed the PCR assay was positive in the oral washes of 29 of the 32 patients with confirmed PCP (sensitivity = 91%) and it was positive in 9 of 143 who had negative BAL assays by direct microscopy (specificity of 94%). The authors conclude that oral washes can provide a useful sample for the diagnosis of PCP by PCR.
Comment: This is an area of great need for new diagnostic tests since PCP remains the most frequent AIDS-defining diagnosis, with about 9,000 cases/year in the U.S., and because there are diagnostic problems due to the highly variable results with induced sputum and the cost and inconvenience of bronchoscopy. Of particular interest in this report is the analysis of the false positive PCR test. Reviews of clinical charts from these patients showed that none developed PCP or were treated for PCP during the next six months, but most (8 of 11) had positive PCR assays of a concurrent sputum or BAL as well. The authors conclude that this probably reflects low levels of organisms and that the high diagnostic accuracy of BAL presumably reflects a relatively high organism load in the presence of active infection.
posted 1/14/2002

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