Rapid PCR Bests Traditional Culture in Correlation of Clinical Variables in Pneumonia

In patients with hospital-acquired pneumonia, bacterial targets and copy numbers detected by the recently FDA-cleared BioFire® FilmArray® pneumonia panel correlated better with patients’ clinical characteristics than traditional microbiologic culture results, according to results of a retrospective study published in Open Forum Infectious Diseases.

Between June and September 2018, investigators analyzed both the pneumonia panel and microbiologic culture results of bronchoalveolar lavage  and endotracheal suction specimens obtained from patients in the intensive care unit. Using a 1-way analysis of variance (ANOVA), they assessed the association between multiple patient clinical variables and pneumonia panel bacterial copy numbers, colony counts for bronchoalveolar lavage specimens, and semiquantitative bacterial growth on plate cultures.

In addition to available clinical data, the investigators’ analysis included unique specimens obtained from 270 patients. Patient mean age was 52 (interquartile range, 40-68) years, and 58.7% were men.

Of the 14 clinical variables tested, results of the pneumonia panel showed a statistically significant association among peak temperature on the day of culture collection, discharge coding for pneumonia, and percentage of polymorphonuclear leukocytes on bronchoalveolar lavage.

There was a statistically significant linear correlation for the distribution of leukocytes detected via Gram stain when the pneumonia panel and culture were both positive (r² =0.9877, P =.0062) and when the pneumonia panel was positive but the culture was uninformative (r² =0.911, P =.0456). Negative pneumonia panel results did not show a statistically significant relationship with the number of leukocytes detected via Gram stain. There was also a statistically significant correlation between the percentage of polymorphonuclear leukocytes on bronchoalveolar lavage and leukocytes detected via  Gram stain (P =.002578).

A positive clinical pulmonary infection score was statistically significantly correlated with a higher proportion of bacterial targets in patients who had positive pneumonia panel and uninformative culture results and those who had positive pneumonia panel and positive culture results (P =.03439).

Despite the strong relationships between the pneumonia panel and important patient inflammatory responses to infection, “positive [pneumonia] panel detections need to be interpreted in the clinical context, even if cultures are discordant,” the investigators noted. However, they also noted that the “rapidly available results” from the pneumonia panel “could potentially reduce diagnostic uncertainty and lead to improved antibiotic stewardship.”

Disclosure: This research was supported by BioFire® Diagnostics, Inc. Please see the original reference for a full list of disclosures.

Reference

Rand KH, Beal SG, Tremblay E, Houck H, Weber K, Sistrom C. Relationship of a multiplex molecular pneumonia panel (PP) results with hospital outcomes and clinical variables. Open Forum Infect Dis. 2021;ofab368. doi:10.1093/ofid/ofab368