Clinical factors influencing the performance of bacterial multiplex polymerase chain reaction in patients with community-onset pneumonia.

The etiologic diagnostic yield of community-onset pneumonia (COP) using conventional methods is low. Bacterial multiplex polymerase chain reaction (mPCR) has been shown to be more sensitive than conventional methods. This study assessed the clinical factors influencing bacterial mPCR results in patients with COP. Patients with COP admitted to a tertiary care hospital between November 2015 and April 2016 were retrospectively assessed. Conventional methods included culture-based methods and serology for Mycoplasma pneumoniae. Bacterial mPCR that could identify Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, and Legionella pneumophilia was performed. Bacterial mPCR was performed in a total of 342 patients with COP in the study. Bacterial mPCR alone provided etiology in 99 patients. The total etiologic diagnosis rates improved from 22.2 to 51.1% when bacterial mPCR was added to conventional methods. Additional diagnostic benefits of bacterial mPCR were more prominent in the prior antibiotic non-exposure group (77.8% vs 63.5%, P = 0.015) and in the low-risk group with low CURB 65 score (62.6% vs 44.9%, P = 0.005). Patients who required ICU care, those with healthcare-associated pneumonia (HCAP), and patients with any underlying diseases were not associated with the additional pathogen detection rates using bacterial mPCR. By supplementing conventional diagnostic methods with bacterial mPCR-based methods, the overall pathogen detection rates improved in patients with COP. Moreover, the additional diagnostic usefulness of bacterial mPCR was significantly higher in patients without prior antibiotic exposure and in the mild-to-moderate-risk group with lower CURB 65 score.