Use of procalcitonin for the diagnosis of pneumonia in patients presenting with a chief complaint of dyspnoea: results from the BACH (Biomarkers in Acute Heart Failure) trial

Abstract

Aims: Biomarkers have proven their ability in the evaluation of cardiopulmonary diseases. We investigated the utility of concentrations of the biomarker procalcitonin (PCT) alone and with clinical variables for the diagnosis of pneumonia in patients presenting to emergency departments (EDs) with a chief complaint of shortness of breath.

Methods and results: The BACH trial was a prospective, international, study of 1641 patients presenting to EDs with dyspnoea. Blood samples were analysed for PCT and other biomarkers. Relevant clinical data were also captured. Patient outcomes were assessed at 90 days. The diagnosis of pneumonia was made using strictly validated guidelines. A model using PCT was more accurate [area under the curve (AUC) 72.3%] than any other individual clinical variable for the diagnosis of pneumonia in all patients, in those with obstructive lung disease, and in those with acute heart failure (AHF). Combining physician estimates of the probability of pneumonia with PCT values increased the accuracy to >86% for the diagnosis of pneumonia in all patients. Patients with a diagnosis of AHF and an elevated PCT concentration (>0.21 ng/mL) had a worse outcome if not treated with antibiotics (P = 0.046), while patients with low PCT values (<0.05 ng/mL) had a better outcome if they did not receive antibiotic therapy (P = 0.049).

Conclusion: Procalcitonin may aid in the diagnosis of pneumonia, particularly in cases with high diagnostic uncertainty. Importantly, PCT may aid in the decision to administer antibiotic therapy to patients presenting with AHF in which clinical uncertainty exists regarding a superimposed bacterial infection.

Trial registration: ClinicalTrials.gov NCT00537628.

Figure 1

Receiver operating characteristic (ROC) curves for the diagnosis of pneumonia (n = 155 events), comparing procalcitonin (PCT), the multivariable model including clinical signs, as well as the clinical signs model plus PCT.

Figure 2

Distribution of patients based on physician-estimated probability of pneumonia (low, medium, and high) and how this distribution would shift if a procalcitonin (PCT) concentration of <0.25 ng/mL was adopted as a model to rule out pneumonia.

Figure 3

Kaplan–Meier plot of procalcitonin (PCT) quintiles for patients diagnosed with acute heart failure (AHF). PCT was significantly associated with 90-day all-cause mortality for patients diagnosed with AHF (Cox regression, χ² 9.2, P = 0.0024).

Figure 4

Kaplan–Meier plot for antibiotic treatment and all-cause mortality within 90 days for patients with acute heart failure (A; all AHF patients) and subgrouped by procalcitonin (PCT) quintiles: PCT > 0.21 ng/mL (B; highest quintile, P = 0.049), between 0.05 and 0.21 (C; P = 0.36, summarizing quintiles 2–4), and <0.05 ng/mL (D; lowest quintile, P = 0.046). Survival rate is adjusted for covariates; see Methods.

Figure 5

Median procalcitonin (PCT) and mid-regional pro atrial natriuretic peptide (MR-proANP) concentrations (left), as well as median PCT and brain natriuretic peptide (BNP) concentrations (right) for patients with acute heart failure (AHF) alone, pneumonia alone, AHF and pneumonia, and those without either condition. The median and interquartile range (IQR) for PCT (in ng/mL) in the four subgroups were as follows: no AHF, no pneumonia 0.06 (0.04–0.09); pneumonia, no AHF 0.23 (0.07–0.92); AHF, no pneumonia 0.09 (0.06–0.16); and AHF and pneumonia 0.14 (0.09–0.26). For MR-proANP (in pmol/L): no AHF, no pneumonia 84 (47–183); pneumonia, no AHF 141 (62–240); AHF, no pneumonia 417 (277–620); and AHF and pneumonia 398 (279–635). For BNP (in ng/mL): no AHF, no pneumonia 50 (20–166); pneumonia, no AHF 122 (37–292); AHF, no pneumonia 766 (409–1461); and AHF and pneumonia 400 (210–857).