A Prospective, Blinded Study of Quantitative Touch‐Down Polymerase Chain Reaction Using Oral‐Wash Samples for Diagnosis ofPneumocystisPneumonia in HIV‐Infected Patients

Oral-wash samples obtained during 113 episodes of suspected Pneumocystis pneumonia (PCP) in human immunodeficiency virus-infected patients were tested by use of a quantitative touch-down PCR (QTD PCR) assay. QTD PCR had a sensitivity of 88% and a specificity of 85%. Treatment for PCP prior to oral wash collection had an impact on the sensitivity, and PCR-positive oral-wash samples obtained within < or =1 day of treatment from patients without PCP had significantly fewer copies per tube than did those from patients with PCP; thus, application of a post hoc cut-off value of 50 copies/tube increased the specificity to 100%. QTD PCR of oral-wash samples can be an accurate and noninvasive method for diagnosis of PCP.