Procalcitonin as an Early Marker of the Need for Invasive Respiratory or Vasopressor Support in Adults With Community-Acquired Pneumonia

Abstract

Background: Predicting the need for intensive care among adults with community-acquired pneumonia (CAP) remains challenging.

Methods: Using a multicenter prospective cohort study of adults hospitalized with CAP, we evaluated the association of serum procalcitonin (PCT) concentration at hospital presentation with the need for invasive respiratory or vasopressor support (IRVS), or both, within 72 h. Logistic regression was used to model this association, with results reported as the estimated risk of IRVS for a given PCT concentration. We also assessed whether the addition of PCT changed the performance of established pneumonia severity scores, including the pneumonia severity index and the American Thoracic Society minor criteria, for prediction of IRVS.

Results: Of 1,770 enrolled patients, 115 required IRVS (6.5%). Using the logistic regression model, PCT concentration had a strong association with IRVS risk. Undetectable PCT (< 0.05 ng/mL) was associated with a 4% (95% CI, 3.1%-5.1%) risk of IRVS. For concentrations < 10 ng/mL, PCT had an approximate linear association with IRVS risk: for each 1 ng/mL increase in PCT, there was a 1% to 2% absolute increase in the risk of IRVS. With a PCT concentration of 10 ng/mL, the risk of IRVS was 22.4% (95% CI, 16.3%-30.1%) and remained relatively constant for all concentrations > 10 ng/mL. When added to each pneumonia severity score, PCT contributed significant additional risk information for the prediction of IRVS.

Conclusions: Serum PCT concentration was strongly associated with the risk of requiring IRVS among adults hospitalized with CAP and is potentially useful for guiding decisions about ICU admission.

Keywords: biomarkers; pneumonia; prognosis; respiratory failure; septic shock.

Figure 1

Nonparametric ROC curves for PCT and WBC count to identify patients who needed IRVS within 72 h. Selected PCT cut points at the 50th, 75th, 90th, and 95th percentiles of PCT concentration in the population are noted on the PCT curve. IRVS = invasive respiratory or vasopressor support; PCT = procalcitonin; ROC = receiver operating characteristic.

Figure 2

Risk of IRVS within 72 h of hospital presentation according to initial serum PCT concentration. The plot was truncated at a PCT concentration of 25 ng/mL because of the small number of patients with PCT concentrations > 25 ng/mL. The 95% CI band is denoted with red shading. See Figure 1 legend for expansion of abbreviations.

Figure 3

Relative contribution of PCT concentration and each of the American Thoracic Society (ATS) minor criteria to the prediction model for IRVS. The ATS minor criteria include AMS, partial pressure of oxygen to fraction of inspired oxygen ratio ≤ 250 (P:F), RR ≥ 30/min (RR), systolic BP < 90 mm Hg (BP), multilobar pulmonary infiltrates (Multilobar), platelets < 100,000 cells/mm³ (PLT); BUN ≥ 20 mg/dL (BUN); temperature < 36° C (Temp); WBC count < 4,000 cells/mm³ (WBC). AMS = altered mental status; RR = respiratory rate. See Figure 1 legend for expansion of other abbreviations.

Figure 4

Risk of IRVS within 72 h of hospital presentation according to initial serum PCT concentration with the study population stratified into low- and high-risk subgroups by (A) ATS minor criteria, (B) PSI, and (C) SMART-COP. Plots were truncated at a PCT concentration of 25 ng/mL because of the small number of patients with PCT concentrations > 25 ng/mL. The 95% CI band is denoted with red shading. Dashed lines represent IRVS risk in a subgroup alone without considering PCT concentration. ATS = American Thoracic Society; PSI = pneumonia severity index. See Figure 1 legend for expansion of other abbreviations.

Figure 5

Classification tree using a combination of ≥ 3 ATS minor criteria or PCT ≥ 0.83 ng/mL (which was the 75th percentile of PCT concentration in the study population) as high-risk indicators for IRVS among adults hospitalized with CAP. CAP = community-acquired pneumonia. See Figure 1 and 4 legends for expansion of other abbreviations.