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Steven Burdette


increasing antibiotic resistant microbes.1 Blood and sputum cultures are the gold standard for bacterial identification, but they are difficult to obtain and take days to receive back from the lab. Physicians commonly treat patients empirically with antibiotics because there is an increased risk of 30-day mortality in patients with bacterial community-acquired pneumonia (CAP).2 Overuse of antibiotics is commonplace in hospitalized patients which is detrimental as it contributes to antibiotic resistance, costs money, wastes resources, and puts patients at risk for unnecessary adverse effects of the medications.3 It was found that 75% of patients presenting with a respiratory tract infection receive antibiotics despite evidence of viral etiology.4

Various biomarkers have been used to try to distinguish between bacterial and viral infections, including procalcitonin (PCT) which is a peptide precursor of calcitonin. Evidence shows that PCT is undetectable in healthy individuals and increases in response to bacterial toxins and cytokines, but not to virally stimulated interferon-γ.5 PCT’s highly sensitive response to bacterial infections makes it superior to other inflammatory biomarkers such as C-reactive protein and erythrocyte sedimentation rate.3,4 PCT levels change in response to therapeutic treatment, increasing with bacterial infection and decreasing upon recovery, making them exceptional markers to monitor treatment.6 Levels are measured upon admission and are taken serially throughout hospitalization.3 PCT becomes measurable in the serum within 2-4 hours of inflammatory response to infection peaking after 12 hours.4 PCT is a marker for systemic infection, as levels are normal or undetectable in healthy patients and patients with mild-to-moderate acute respiratory infection (ARI).7 PCT levels were also associated with a higher mortality risk in severe infection.6

Being highly sensitive to bacterial infection and responsive to treatment, PCT can be used to determine when antibiotics should be prescribed or discontinued in respiratory illnesses.4 Antibiotics were discouraged for PCT levels <0.25 ng/mL and encouraged for levels >0.25 ng/mL, while normal is <0.03 ng/mL.8 Following these criteria, antibiotics were reduced by 72% without a change in patient morbidity, treatment failure, or mortality.9