Low sensitivity of a nested polymerase chain reaction in oropharyngeal washings for the diagnosis of pneumocystis pneumonia in HIV-infected patients.

STUDY

OBJECTIVE

To compare the relative yield and diagnostic utility of the polymerase chain reaction (PCR) analysis for Pneumocystis jirovecii DNA in oropharyngeal washings using transbronchial biopsy (TBBx) and BAL as "gold standards."

DESIGN

Prospective study.

SETTING

Academic tertiary center.

PATIENTS: Oropharyngeal washes were obtained in 50 consecutive patients with clinical pneumocystis pneumonia (PCP). Because of varying clinical severity, not all patients tolerated bronchoscopy. Thirty-five patients underwent TBBx, and 48 patients underwent BAL.

METHODS

DNA extracted from oropharyngeal washings and BAL was subjected to a nested PCR test using primers for the large subunit mitochondrial ribosomal RNA of P jirovecii. Oropharyngeal washings were compared with BAL PCR and TBBx.

RESULTS

Sixteen of the 35 TBBx procedures had positive results for PCP (46%). Oropharyngeal washings yielded positive results for pneumocystis in 7 of the 16 patients (sensitivity, 44%; specificity, 79%). Thirty-five of 48 patients (73%) had positive PCR results on BAL analysis. The relative yield of the PCR in oropharyngeal washes compared with BAL fluid was 40% (14 of 35 washes), giving a sensitivity of 40% and specificity of 77%.

CONCLUSION

PCR DNA amplification of oropharyngeal washings in HIV-seropositive subjects has a low sensitivity and specificity for the diagnosis of PCP.