Outcomes Research in Review

Procalcitonin, Will It Guide Us?

Huang DT, Yealy DM, Filbin MR, et al. Procalcitonin-guided use of antibiotics for lower respiratory tract infection. New Engl J Med. 2018;379:236-249.



Study Overview

Objective. To assess whether procalcitonin-guided antibiotic usage results in less exposure to antibiotics than usual care, without a significantly higher rate of adverse events.

Design. Multi-center 1:1 randomized trial.

Setting and participants. This study was conducted at 14 academic hospitals in the United States between 2014 and 2017 in which procalcitonin assay was not routinely used. All adult patients in the emergency department with an initial diagnosis of acute lower respiratory tract infection without a decision to give or withhold antibiotics because of uncertainty regarding the need for antibiotics were included in the study. Patients were excluded if antibiotics were unlikely to be held in their case, such as if there was a need for mechanical ventilation or known severe immunosuppression, and if procalcitonin could be falsely elevated (chronic dialysis, metastatic cancer, surgery in the past 7 days).

Intervention. Patients were randomly assigned to receive guideline-based care using procalcitonin (procalcitonin group) or usual care (usual-care group). In the procalcitonin group, the procalcitonin assay results, and the procalcitonin treatment guidelines were provided to the treating physician. The guideline used previously established cutoffs (procalcitonin level of < 0.1 µg/L, antibiotics were strongly discouraged; 0.1 to 0.25 µg/L, antibiotics were discouraged; 0.25 to 0.5 µg/L, antibiotics were recommended; and > 0.5 µg/L, antibiotics were strongly recommended). Procalcitonin was measured initially in the emergency department. If the patient was hospitalized, procalcitonin was again measured 6 to 24 hours later, and on hospital days 3, 5, and 7. To implement this intervention, a multifaceted approach was used, which included sending letters to local primary care providers describing the trial, ensuring rapid delivery of procalcitonin results by tracking and coordinating blood samples with routine morning draws, and embedding the procalcitonin results and guidelines into the sites’ electronic health records. In the usual-care group, procalcitonin levels at enrollment were measured but not disclosed to clinicians. In both treatment groups, clinicians retained autonomy regarding care decisions.

Main outcome measures. The primary outcome was total antibiotic exposure, defined as the total number of antibiotic-days within 30 days after enrollment. The primary safety outcome was any adverse effects that could be attributable to withholding antibiotics in lower respiratory tract infections, within 30 days after enrollment. Secondary outcomes included admission to the intensive care unit (ICU), subsequent emergency department visits by day 30, and quality of life as assessed with the Airway Questionnaire 20.

Main results. 8360 patients with acute lower respiratory tract infection who presented to the emergency department were screened for eligibility; of these, 1664 patients underwent randomization. Ultimately, 1656 patients were included in the final analysis cohort (826 in the procalcitonin group and 830 in the usual-care group), because 8 patients withdrew. Of the cohort, 1345 (81.2%) patients completed the full 30-day follow up. Baseline characteristics were similar between the treatment groups. In the procalcitonin group, clinicians received the procalcitonin results for 95.9% of the patients. As a result of clinical care, 2.2% of the patients in the usual-care group also had procalcitonin testing. Clinicians adhered to the procalcitonin guideline recommendations for 64.8% of the procalcitonin group.

There was no significant difference in the intention-treat-treat analysis between the procalcitonin group and the usual-care group in antibiotic days during the first 30 days (mean antibiotic days, 4.2 and 4.3 days, respectively [95% confidence interval {CI}, –0.6 to 0.5; P = 0.87]). Within 30 days there was no significant difference in the proportion of patients with adverse outcomes in the procalcitonin group and usual-care group (11.7% and 13.1%, respectively [95% CI, –4.6 to 1.7]; P < 0.01 for noninferiority). There was no significant difference between the procalcitonin and usual-care groups for any of the secondary outcomes.

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