Clinical Progress Note: Procalcitonin in the Management of Pediatric Lower Respiratory Tract Infection

In the study by Esposito et al., the PCT levels were additionally measured every two days until discharge and during two scheduled follow-up visits; the antibiotics were discontinued when PCT < 0.25 µg/L.² The PCT-guided group experienced shorter antibiotic duration (mean 5.4 vs 11.0 days, P < .05), shorter length of hospital stay (mean 4.7 vs 5.61 days for mild LRTI and 5.01 vs 5.93 for severe LRTI), and fewer antibiotic-related adverse events (3.9% vs 25.2%, P < .05). Similarly, in the study by Baer et al., the PCT-guided group had PCT levels repeated on days three and five after enrollment, and the antibiotics were discontinued when PCT was less than 0.25 µg/L. The duration of antibiotic administration was significantly lower in the PCT-guided group (mean difference: 1.8 days, 95% CI: −3.1, −0.).³ The rates of hospitalization, duration of hospital stay, and mean impairment of daily activities attributable to LRTI were similar between groups.

Considering the adult studies and the small number of pediatric LRTI research published to date, the use of PCT to safely reduce antibiotic treatment duration is encouraging.⁴ Although the studies on the kinetics of PCT are limited, the biomarker has been shown to rise two to four hours after a bacterial stimulus, peak in 24-48 hours and achieve a half-life of 24-36 hours.^6,7 As such, serial PCT measurements at 24-hour intervals for three to five days may be more beneficial than stand-alone PCT tests. Nonetheless, additional studies are needed to better define groups of patients who will most likely benefit from PCT testing and to understand how to best integrate testing into clinical practice.

PCT has also been explored as a marker of LRTI disease severity. In a 2008 multicenter cohort encompassing 1,651 adults with pneumonia, PCT < 0.1 µg/L was associated with a decreased 30-day mortality, shorter length of stay, and decreased admission to the intensive care unit (ICU) compared with those with PCT>0.1 µg/L.⁸ In a 2017 study of 317 adults hospitalized with pneumonia, the PCT level was significantly higher in those with bacteremia and in those admitted to intensive care.⁹ When used in combination with the pneumonia severity index (PSI), the addition of PCT resulted in improved prognostic performance compared with the PSI alone for both outcomes, increasing the area under the receiver operating characteristic curve from 0.67 to 0.85 for bacteremia and from 0.58 to 0.64 for intensive care. Similarly, in the adult EPIC cohort, the addition of PCT contributed significant prognostic information beyond existing severity scores for predicting the need for invasive respiratory or vasopressor support; each 1 µg/L increase in PCT was associated with a 1% to 2% absolute increase in the need for this outcome.¹⁰

A European study of 100 children with pneumonia also demonstrated higher PCT values among hospitalized children (n = 26, median PCT 17.8 µg/L) compared with outpatient children (n = 73, median PCT 0.72 µg/L, P < .01).¹¹ Among the 532 children from the EPIC study, a PCT < 0.25 µg/L was associated with the reduced odds of ICU admission (adjusted OR: 0.48; 95% CI: 0.30, 0.78) and a 2.3-day (95% CI: 1.4, 3.2) decrease in the average length of stay compared with those with higher PCT concentrations.⁵ Of the 34 children with empyema requiring drainage, 28 (82%) showed a PCT concentration ≥0.5 µg/L. Additional pediatric studies are needed, but the limited data to date suggest that PCT may play a role in predicting pediatric LRTI disease severity, including the need for mechanical ventilatory support and ICU-level care.