Outpatient Antibiotic Stewardship: A Growing Frontier—Combining Myxovirus Resistance Protein A With Other Biomarkers to Improve Antibiotic Use

Joseph, Patrick; Godofsky, Eliot

URIs tend to cause modest elevations in PCT [42, 43] . Using a lower PCT threshold of 0.1 ng/mL in association with polymerase chain reaction-confirmed bacterial cultures of common oral pathogens such as GABHS or atypical pathogens such as Chlamydophila or Mycoplasma, would suggest a true active bacterial infection. Higher PCT cutoffs of 0.15-0.25 ng/mL could be used in association with growth of typical bacterial colonizers or in association with a negative bacterial culture to suggest active bacterial infection in patients without another confirmed source of infection, such as a viral infection [8, 40] . The PCT response to viral infections and noninfectious inflammatory stimuli such as autoimmune disease and chronic inflammatory processes typically do not exceed 0.75 ng/mL [44, 45] . Branch et al. found that 17% of viral infections had a PCT >0.25 ng/mL [46] . At low concentrations (<1.0 ng/mL), PCT is inadequate by itself to differentiate viral from bacterial etiology [8, 47, 48] .