Infectious Disease

Biomarker may curb unnecessary antibiotic use for lower respiratory tract infection

January 03, 2023

2 min read

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Disclosures:
Tsalik reports consulting for Biomeme and has a patent pending for Methods to Diagnose and Treat Acute Respiratory Infections. Please see the study for all other authors’ relevant financial disclosures.

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Patients with lower respiratory tract infections and low procalcitonin levels treated with placebo improved at rates similar to those given azithromycin, with fewer side effects and less antibiotic exposure, a recent study showed.

“The study was prompted by a few factors — first is the overuse of antibiotics and the contribution this makes to worsening antimicrobial resistance; second is the availability of a biomarker, procalcitonin, to help discriminate bacterial from viral infection; third is that prior studies of procalcitonin showed it could safely reduce unnecessary antibiotic use although physicians could overrule the test recommendations and give antibiotics anyway,” Ephraim L. Tsalik, MD, PhD, chief scientific officer for infection disease diagnostic at Danaher Diagnostics and adjunct professor at the Duke University Medical Center, told Healio. “As a result, no one has ever shown that low levels of this biomarker (suggesting the absence of a bacterial infection) can be safely used to limit antibiotic exposure. We conducted this trial to directly answer that question.”

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Patients with upper respiratory tract infections treated with placebo improved at rates similar to those given azithromycin. Source: Adobe Stock

Tsalik and colleagues performed a randomized, placebo-controlled, double-blind, noninferiority trial at five US health centers, consisting of adults aged 18 years or older with clinically suspected nonpneumonia lower respiratory tract infection and symptom duration from 24 hours to 28 days.

According to the study, participants with a procalcitonin concentration of 0.25 ng/mL or less were 1:1 to receive over-encapsulated oral azithromycin 250 mg or matching placebo. The primary outcome was efficacy of azithromycin placebo in terms of clinical improvement at day 5 in the intention-to-treat population.

Between Dec 8, 2017, and March 9, 2020, 499 patients were enrolled with 249 randomly assigned to receive azithromycin and 250 placebo.

Clinical improvement at day 5 was observed in 63% (95% CI, 54-71) of 238 participants with full data in the placebo group and 69% (95% CI, 61-77) of 227 participants with full data in the azithromycin group in the intention-to-treat analysis, rendering a between-group difference of 6% (95% CI, -152) which did not meet the noninferiority margin, according to the study.

Tsalik added that at day 11, treatment with placebo was considered noninferior despite those treated with antibiotics apparently improving faster at day 5.

Additionally, adverse events and the severity of adverse events were not significantly different between groups at day 5, except for increased abdominal pain associated with azithromycin (47 of 204 participants; 95% CI, 18-29) compared with placebo (35 of 221 participants ; 95% CI, 12-21).

“Decisions about whether to use this biomarker to guide antibiotic use should account for the need to maximize rates of clinical improvement (as in those with severe comorbidities at baseline) while minimizing antibiotic related side effects and trying to decrease unnecessary antibiotic use,” Tsalik said .

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