PROCALCITONIN AND ANTIBIOTIC USE

Procalcitonin to Guide Antibiotic Use in Primary Care

Summary

Respiratory tract infections (RTIs) are among the most common reasons for antibiotic prescription in primary care. A test that can differentiate between bacterial and viral RTIs could help to reduce antibiotic use. Procalcitonin (PCT) levels have been used as a marker for bacterial infection in hospitalized patients but have not been evaluated in the primary care setting. In a recent randomized trial, investigators in Switzerland (1 of whom received research support from the maker of the PCT assay used in the study) compared a PCT-guided approach with standard care among adult outpatients who had acute RTIs. All participants were believed — consistent with evidence-based guidelines — to require antibiotic treatment.

When PCT-arm patients had PCT levels >0.25 µg/L, a bacterial infection was considered likely, and antibiotic prescription was recommended; for lower levels, antibiotic prescription was discouraged. When antibiotics were withheld, a second PCT level was obtained within 6 to 24 hours. If the level was then >0.25 µg/L or had increased by >50% with no clinical improvement, antibiotics were recommended. In addition, all patients prescribed antibiotics based on PCT levels were reassessed after 3 days, and antibiotics were discontinued if the level was ≤0.25 µg/L. The primary outcome measure was the number of days in the first 2 weeks during which daily activities were restricted by an RTI.

Of 458 patients randomized, 455 were evaluated at 2 weeks. The antibiotic-prescription rate was significantly lower in the PCT arm than in the standard-care arm (25% vs. 97%). The number of RTI-restricted days and the rate of ongoing or relapsing infection at 28 days were similar between arms.

Comment

Using PCT level to guide antibiotic therapy for outpatients with RTIs dramatically reduced antibiotic use without increasing the risk for adverse outcomes. These results are even more striking considering that the study enrolled only patients who were believed to need antibiotics by physicians in a country where antibiotic-prescription rates are much lower than in the U.S. As an editorialist notes, wide adoption of this approach requires development of a rapid, accurate, and inexpensive office-based PCT test.