New study targets PCT levels in viral vs bacterial respiratory tract infections

A new clinical trial sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, will evaluate whether low blood levels of the protein procalcitonin (PCT) can reliably indicate whether a lower respiratory tract infection (LRTI) will improve with antibiotic treatment.

Lower respiratory tract infections have a variety of symptoms, including persistent coughing, wheezing, chest pain, fever, and rapid or difficult breathing. Health-care providers often prescribe a course of antibiotics as standard treatment without knowing for certain whether an infection is bacterial or viral. This practice can introduce potential side effects and promote antimicrobial resistance.

Procalcitonin is normally produced in minute quantities in a healthy body. It serves as a precursor to calcitonin, a hormone that helps regulate calcium levels.

Elevated PCT levels are an indicator of bacterial sepsis, a life-threatening complication of infection that triggers inflammation throughout the body. The NIAID researchers leading the new clinical trial theorize that low PCT levels in patients with LRTIs may indicate that the infection is viral, not bacterial.

“Health-care providers and patients benefit from precise diagnostic tests to guide treatment decisions,” said Anthony S. Fauci, MD, director of NIAID. “An effective biomarker for confirming that a lower respiratory tract infection is viral and thus not treatable with antibiotics would be a significant development in our collective efforts to reduce inappropriate use of antibiotics and combat antimicrobial resistance.”

The study is being led by principal investigator Ephraim Tsalik, MD, PhD, associate professor of medicine at Duke University School of Medicine and a physician at the Durham VA Health Care System in Durham, NC. It will enroll patients 18 years of age or older with suspected LRTIs and low PCT blood levels (0.25 ng/mL or less).

After PCT levels have been confirmed, as many as 420 patients will be randomized to receive either a 5-day regimen of the oral antibiotic azithromycin (500 mg as a single dose on day 1 followed by 250 mg once daily for 4 days) or placebo. Patients whose symptoms worsen will be immediately referred for appropriate care.

At day 5, all patients will be evaluated for improvement. Additional follow-up with patients will occur on days 11 and 28 to determine their health status.

If no significant difference in improvement rates is noted between volunteers treated with azithromycin and those receiving placebo, low PCT levels could identify patients who are unlikely to benefit from antibiotic treatment.

Conversely, if the volunteers given antibiotics tend to recover faster or better than those given placebo, the results will indicate that low PCT levels are not a reliable biomarker to guide the use of antibiotics for LRTIs.

The study, which is expected to conclude by 2020, was developed by the NIAID-supported Antibacterial Resistance Leadership Group in collaboration with bioMérieux researchers and medical experts.

It is being conducted through three NIAID-funded Vaccine and Treatment Evaluation Units and three VA Health Care Systems, with a total of five sites enrolling participants in Georgia, North Carolina, and Texas.