Clinical Progress Note: Procalcitonin in the Diagnosis and Management of Community-Acquired Pneumonia in Hospitalized Adults

While initial procalcitonin measurements may not affect the initial antibiotic treatment decision, procalcitonin levels thereafter can guide the duration of therapy. A meta-analysis of procalcitonin-guided treatment in patients with upper or lower respiratory tract infection (LRTI) showed that procalcitonin guidance reduces antibiotic exposure and antibiotic-related adverse effects and improves survival, albeit a small absolute mortality difference of 1.4 percentage points, primarily observed in the intensive care unit setting.⁶ Most patients included in this meta-analysis were diagnosed with LRTI (91%), and CAP was the predominant subtype of LRTI (43%). The main effect of procalcitonin guidance for patients with CAP was earlier discontinuation of antibiotic treatment. Procalcitonin-guided algorithms in these trials discouraged, or strongly discouraged, antibiotics if procalcitonin was <0.25 ng/mL or <0.1 ng/mL, respectively. In addition, serial procalcitonin measurements were used to guide discontinuation of antibiotics if procalcitonin dropped below 0.25 ng/mL, or by 80% to 90% from the peak value. This approach safely shortened the duration of therapy in patients with CAP.

There are several limitations in the interpretation and generalizability of this meta-analysis. There is large heterogeneity across the included clinical trials in design, procalcitonin protocols, clinical setting, and respiratory infection type, including bronchitis, acute exacerbation of chronic obstructive pulmonary disease (AECOPD), and CAP. Results were consistent only in one moderate- to high-quality randomized trial specifically studying CAP in the inpatient setting.⁷ Additionally, most of these trials were conducted in Europe. Antibiotic prescribing practices may be different in the US, and prescribing practices on both continents may have changed over the years with greater awareness and appreciation of antibiotic stewardship.

The ProACT trial, the largest randomized, US multicenter trial to evaluate a procalcitonin-based algorithm to assist with antibiotic decision making, included over 1,600 emergency department patients at 14 academic medical centers.⁸ Procalcitonin guidance in this trial did not reduce antibiotic exposure compared with usual care for patients with suspected LRTI. However, its applicability to the practice of hospitalists and the inpatient setting is limited. First, only 48% of the study participants required hospitalization. Second, this study included all LRTIs, with CAP comprising just 20% of all final diagnoses. Third, the average number of antibiotic days during hospitalization for CAP was short in both groups (3.9 days in the procalcitonin group and 4.1 days in the usual care group). This relatively short antibiotic duration makes it difficult for any intervention to decrease antibiotic days meaningfully.

In a prepost controlled intervention study for inpatients at a single US tertiary care hospital, procalcitonin guidance in hospitalized patients safely reduced antibiotic use in LRTI, specifically for the discontinuation of antibiotics.⁹ The greatest benefit of procalcitonin guidance in antibiotic discontinuation was found in patients with AECOPD and patients with an admitting diagnosis of CAP, but with mild illness and a low procalcitonin. Although this prepost study suggested a safe reduction of antibiotic use due to implementation of procalcitonin guidance, the lack of randomization and the absence of a contemporaneous control group are important limitations. Given the mixed findings on the effectiveness of procalcitonin guidance for hospitalized CAP patients in the US, further investigation will be needed with large clinical trials in the inpatient setting for CAP.