Conference Coverage

Next-gen sputum PCR panel boosts CAP diagnostics



– A next-generation lower respiratory tract sputum polymerase chain reaction (PCR) film array panel identified etiologic pathogens in 100% of a group of patients hospitalized for community-acquired pneumonia, Kathryn Hendrickson, MD, reported at the annual meeting of the American College of Physicians.

Legionella sp. colonies growing on an en:agar plate and illuminated using ultraviolet light to increase contrast. Courtesy CDC

The investigational new diagnostic assay, the BioFire Pneumonia Panel, is now under Food and Drug Administration review for marketing clearance. It offers great potential for targeted therapy along with reduced overuse of antibiotics in patients with community-acquired pneumonia (CAP), observed Dr. Hendrickson, an internal medicine resident at Providence Portland (Ore.) Medical Center. The new product is designed to complement the currently available respiratory panels from BioFire.

“Rapid-detection results in less empiric antibiotic use in hospitalized patients. When it’s FDA approved, this investigational sputum PCR panel will simplify the diagnostic bundle while improving antibiotic stewardship,” she observed.

She presented a prospective study of 63 patients with CAP hospitalized at the medical center, all of whom were evaluated by two laboratory methods: the hospital’s standard bundle of diagnostic tests and the new BioFire film array panel. The purpose was to determine if there was a difference between the two tests in the detection rate of viral and/or bacterial pathogens as well as the clinical significance of any such differences; that is, was there an impact on days of treatment and length of hospital stay?

Traditional diagnostic methods detect an etiologic pathogen in at best half of hospitalized CAP patients, and the results take too much time. So Providence Portland Medical Center adopted as its standard diagnostic bundle a nasopharyngeal swab and a BioFire film array PCR that’s currently on the market and can detect nine viruses and three bacteria, along with urine antigens for Legionella sp. and Streptococcus pneumoniae, nucleic acid amplification testing for S. pneumoniae and Staphylococcus aureus, and blood and sputum cultures. In contrast, the investigational panel probes for 17 viruses, 18 bacterial pathogens, and seven antibiotic-resistant genes; it also measures procalcitonin levels in order to distinguish between bacterial colonization and invasion.

The new BioFire Pneumonia Panel detected a mean of 1.4 species of pathogenic bacteria in 79% of patients, while the standard diagnostic bundle detected 0.7 species in 59% of patients. The investigational panel identified a mean of 1.0 species of viral pathogens in 86% of the CAP patients; the standard bundle detected a mean of 0.6 species in 56%.

All told, any CAP pathogen was detected in 100% of patients using the new panel, with a mean of 2.5 different pathogens identified. The standard bundle detected any pathogen in 84% of patients, with half as many different pathogens found, according to Dr. Hendrickson.

A peak procalcitonin level of 0.25 ng/mL or less, which was defined as bacterial colonization, was associated with a mean 7 days of treatment, while a level above that threshold was associated with 11.3 days of treatment. Patients with a peak procalcitonin of 0.25 ng/mL or less had an average hospital length of stay of 5.9 days, versus 7.8 days for those with a higher procalcitonin indicative of bacterial invasion.

The new biofilm assay reports information about the abundance of 15 of the 18 bacterial targets in the sample. However, in contrast to peak procalcitonin, Dr. Hendrickson and her coinvestigators didn’t find this bacterial quantitation feature to be substantially more useful than a coin flip in distinguishing bacterial colonization from invasion.

She reported having no financial conflicts regarding the head-to-head comparative study, which was supported by BioFire Diagnostics.

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