Procalcitonin for diagnosis of bacterial pneumonia in critically ill patients during 2009 H1N1 influenza pandemic: a prospective cohort study, systematic review and individual patient data meta-analysis

Abstract

Introduction: Procalcitonin (PCT) is helpful for diagnosing bacterial infections. The diagnostic utility of PCT has not been examined thoroughly in critically ill patients with suspected H1N1 influenza.

Methods: Clinical characteristics and PCT were prospectively assessed in 46 patients with pneumonia admitted to medical ICUs during the 2009 and 2010 influenza seasons. An individual patient data meta-analysis was performed by combining our data with data from five other studies on the diagnostic utility of PCT in ICU patients with suspected 2009 pandemic influenza A(H1N1) virus infection identified by performing a systematic literature search.

Results: PCT levels, measured within 24 hours of ICU admission, were significantly elevated in patients with bacterial pneumonia (isolated or coinfection with H1N1; n = 77) (median = 6.2 μg/L, interquartile range (IQR) = 0.9 to 20) than in patients with isolated H1N1 influenza pneumonia (n = 84; median = 0.56 μg/L, IQR = 0.18 to 3.33). The area under the curve of the receiver operating characteristic curve of PCT was 0.72 (95% confidence interval (CI) = 0.64 to 0.80; P < 0.0001) for diagnosis of bacterial pneumonia, but increased to 0.76 (95% CI = 0.68 to 0.85; P < 0.0001) when patients with hospital-acquired pneumonia and immune-compromising disorders were excluded. PCT at a cut-off of 0.5 μg/L had a sensitivity (95% CI) and a negative predictive value of 80.5% (69.9 to 88.7) and 73.2% (59.7 to 84.2) for diagnosis of bacterial pneumonia, respectively, which increased to 85.5% (73.3 to 93.5) and 82.2% (68.0 to 92.0) in patients without hospital acquired pneumonia or immune-compromising disorder.

Conclusions: In critically ill patients with pneumonia during the influenza season, PCT is a reasonably accurate marker for detection of bacterial pneumonia, particularly in patients with community-acquired disease and without immune-compromising disorders, but it might not be sufficient as a stand-alone marker for withholding antibiotic treatment.

Figure 1

Flowchart used for systematic literature search.

Figure 2

Procalcitonin and C-reactive protein levels by status of bacterial pneumonia (isolated bacterial or mixed bacterial and H1N1 infection versus isolated H1N1). (A) Procalcitonin. (B) C-reactive protein box representing interquartile range, line subdividing box representing median, whisker span all values within 1.5 interquartile ranges of the nearer quartile.

Figure 3

Area under the receiver operating characteristic curves for detection of bacterial pneumonia by procalcitonin. (A) Area under the receiver operating characteristic curve (AUC) with 95% confidence interval (CI) representing data from the total study population. (B) AUC with 95% CI representing data from patients without hospital-acquired pneumonia or immune-compromising disease.