Procalcitonin is not an independent predictor of 30-day mortality, albeit predicts pneumonia severity in patients with pneumonia acquired outside the hospital

Abstract

Background: Procalcitonin (PCT) is a useful marker for pneumonia. However, its clinical usefulness in elderly patients has not been studied extensively. This study aimed to assess the relationship between PCT and prognosis and pneumonia severity in elderly patients with pneumonia acquired outside the hospital.

Methods: Data considered relevant to pneumonia severity and prognosis were retrospectively obtained from clinical charts of all patients with pneumonia who were admitted to our hospital from 2010 to 2017. The primary outcome was 30-day mortality in elderly patients (aged ≥75 years), and the relationship between PCT levels and pneumonia severity, as determined by the pneumonia severity index (PSI) was also examined.

Results: Data were collected from 667 patients, of which 436 were elderly patients. Multivariate and receiver operating characteristic curve analysis revealed that albumin, body mass index, and PSI class rather than PCT are important factors related to 30-day mortality in elderly patients. PCT was also not an independent prognostic factor in younger patients. PCT levels significantly differed by pneumonia severity (mild, moderate, and severe) in both younger (p < 0.001) and elderly (p < 0.0001) patients, with levels increasing as severity increased. In contrast, C-reactive protein (CRP) levels and white blood cell counts did not significantly differ by pneumonia severity in younger and elderly patients. A subgroup analysis focused on Streptococcus pneumoniae pneumonia revealed that PCT levels differed by severity in elderly patients (p = 0.03), with levels increasing as severity increased.

Conclusion: PCT was not an independent predictor of 30-day mortality in both of elderly and younger patients. PCT levels, but not CRP levels, significantly increased with increasing pneumonia severity in younger and elderly patients, although the degree of increase tended to be lower in elderly patients compared to younger patients for the same severity. PCT levels also significantly increased with increasing pneumonia severity in elderly patients with Streptococcus pneumoniae pneumonia.

Keywords: C-reactive protein; Elderly; Pneumonia; Pneumonia severity; Procalcitonin; Prognosis.

Fig. 1

Receiver operating characteristic curve of procalcitonin (PCT) levels, white blood cell (WBC) counts, C-reactive protein (CRP) levels, age, Charlson comorbidity index (CCI), blood urea nitrogen (BUN), pneumonia severity index (PSI) class, body mass index (BMI), and albumin levels for prediction of 30-day mortality of patients younger than 74 years

Fig. 2

Receiver operating characteristic curve of age, Charlson comorbidity index (CCI), procalcitonin (PCT) levels, white blood cell (WBC) counts, C-reactive protein (CRP) levels, blood urea nitrogen (BUN), pneumonia severity index (PSI) class, body mass index (BMI), and albumin levels for prediction of 30-day mortality of patients older than 75 years

Fig. 3

Box plots showing procalcitonin (PCT) levels, C-reactive protein (CRP) levels, and white blood cell (WBC) counts according to pneumonia severity determined by the pneumonia severity index of younger (≤74 years old) and elderly (≥75 years old) patients with pneumonia occurring outside the hospital setting. The box plots show 25th, 50th, and 75th percentiles, and outliers. *: p < 0.05, **: p < 0.01

Fig. 4

Box plots showing procalcitonin (PCT) levels, C-reactive protein (CRP) levels, and white blood cell (WBC) counts according to pneumonia severity determined by the pneumonia severity index of elderly (≥75 years old) patients with Streptcoccus pneumoniae pneumonia occurring outside the hospital setting. The box plots show 25th, 50th, and 75th percentiles, and outliers. **: p < 0.01