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Procalcitonin Assay Produces Few Changes in Antibiotic Use, Study Finds

NEW YORK (360Dx) – The use of a US Food and Drug Administration-cleared procalcitonin assay had no effect on the rate in which doctors prescribed antibiotics to patients suspected of having lower respiratory tract infections, researchers from the University of Pittsburgh School of Medicine reported on Sunday.  

In a study published in the New England Journal of Medicine, the researchers looked at 1,656 adult patients enrolled in 14 predominately urban academic hospitals who presented to the hospital emergency department. Initially diagnosed with lower respiratory tract infections, their procalcitonin levels were tested with the FDA-cleared BioMérieux procalcitonin assay.

The UPitt researchers said they found no significant difference in antibiotic use between the group of physicians who were given test results for the patients they treated (the procalcitonin group), and the group of patients who did not know the test outcome of the patients that they treated (the usual-care group). This finding runs counter to previous research that had found that using a procalcitonin assay to guide treatment had "reduced the use of antibiotics with no apparent harm," the researchers noted in their paper.

The work was conducted as part of the Procalcitonin Antibiotic Consensus Trial, a five-year multicenter study to evaluate the effect of a procalcitonin antibiotic prescribing guideline. The primary outcome of the NEJM study was total antibiotic exposure, or the total number of antibiotic days — defined as any day in which a patient received antibiotics — within 30 days after enrollment.

At the start of the work, the scientists hypothesized that the total number of antibiotic days would be lower, "and the percentage of patients with adverse outcomes would not be more than 4.5 percentage points higher" in the procalcitonin group than in the usual-care group.

The researchers provided guidance to clinicians about national clinical practice recommendations for treating lower respiratory tract infections and interpreting procalcitonin assays. Of the 1,656 patients in the study, 782, or 47.2 percent, were hospitalized, and 984 (59.4 percent) received antibiotics within 30 days.

The 1,656 patients were randomly assigned to two groups: 826 were assigned to a procalcitonin group, for which the treating clinicians were provided with real-time initial, and in some cases serial, procalcitonin assay results; and 830 were assigned to a usual-care group.

The treating physicians received the test results for 792 of the 826 patients (95.9 percent) in the procalcitonin group, while treating physicians received test results for 18 of the 830 patients (2.2 percent) in the usual-care group.

The UPitt team found that there was no significant difference in the antibiotic days between the procalcitonin group and the usual-care group (4.2 days vs. 4.3 days). Among secondary outcomes, they similarly noticed "no significant difference" between the two groups. For example, 57 percent of patients in the procalcitonin group received antibiotics within 30 days of enrollment, compared to 61.8 percent of patients in the usual-care group. Meanwhile, 34.1 percent of the procalcitonin group received an antibiotic prescription in the emergency department compared to 38.7 percent in the usual-care group; and the mean hospital antibiotic days among hospitalized patients in the procalcitonin group was 2.6 days compared to 2.7 days in the usual-care group.

However, for acute bronchitis, the percentage of patients in the procalcitonin group who received an antibiotic prescription was notably lower than in the usual-care group, 17.3 percent vs. 32.1 percent.

The researchers reported "no significant difference" in the quality of life between the two groups, and the rate of serious adverse events did not differ between the groups, they said.

The reasons for the discrepancy between the UPitt researchers' results and earlier studies that suggested the use of a procalcitonin assay led to lower antibiotic use, they said, may be attributed, in part, to differences in case mix, design, and setting. They also noted that a decade has passed since the last large trial was conducted exploring the effect of procalcitonin testing on antibiotic use, and greater awareness of antibiotic overuse and stewardship may have changed prescribing habits.

In a statement, UPitt further said that the researchers found that procalcitonin test results "generally matched up with how sick a patient looked as well as their physician's judgment on how likely it was they had bacterial infections."

"In other words, it seems likely that physicians already commonly withheld antibiotics based on clinical signs alone, and, therefore, instead of the magic bullet I and many others hoped procalcitonin might be, it offered only limited incremental value over clinical judgment," David Huang, lead author on the NEJM study and an associate professor of critical care medicine and emergency medicine at the UPitt School of Medicine, said in the statement.