Evaluation of the diagnostic usefulness of real-time PCR for detection of Chlamydophila pneumoniae in acute respiratory infections.

We investigated whether a real-time polymerase chain reaction (PCR) test is a useful diagnostic tool for identifying individuals with acute respiratory Chlamydophila pneumoniae infections. Nasopharyngeal swab specimens and peripheral blood mononuclear cells (PBMCs) from 100 patients with acute respiratory tract infections and 140 asymptomatic healthy subjects (controls) were analyzed using real-time PCR, culture, and serology for the detection of C. pneumoniae. Six patients had serological results indicating acute C. pneumoniae infections. C. pneumoniae DNA was detected in respiratory samples from eight patients (three of these cases were serologically confirmed as having C. pneumoniae infections) and four controls. The amount of C. pneumoniae DNA present in the real-time PCR for the samples was calculated, and no significant differences in the amount of DNA between symptomatic and asymptomatic subjects were found. On the other hand, traces of C. pneumoniae DNA were detected in PBMCs from eight patients, but this was confirmed in PBMCs from only seven of these patients. Only one patient had both respiratory and blood samples that were positive. C. pneumoniae DNA was also detected in samples from six controls, but no significant differences in the amount of C. pneumoniae DNA were observed between patients and controls. The present quantitative real-time PCR assay does not seem to be a useful method for differentiating between C. pneumoniae acute infections and persistent ones or nasopharyngeal carriage. In addition, the detection of C. pneumoniae DNA in PBMCs does not seem to be a suitable method for the diagnosis of acute respiratory C. pneumoniae infections.