Calprotectin as an early biomarker of bacterial infections in critically ill patients: an exploratory cohort assessment

Crit Care Resusc. 2017 Sep;19(3):205-213.


Background: Calprotectin is the most abundant protein in the cytosolic fraction of neutrophils, and neutrophil degranulation is a major response to bacterial infections.

Objectives: To assess the value of plasma calprotectin as an early marker of bacterial infections in critically ill patients and compare it with the corresponding values for procalcitonin (PCT), C-reactive protein (CRP) and white blood cell count (WBC).

Methods: We measured daily plasma calprotectin levels in 110 intensive care unit patients using a newly developed turbidimetric assay run on clinical chemistry analysers. The likelihood of infection was determined according to the International Sepsis Forum criteria.

Results: Overall, 58 patients (52.7%) developed a suspected or confirmed bacterial infection. Plasma calprotectin predicted such infections within 24 hours with an area under the receiver operating characteristics curve (ROC area) of 0.78 (95% CI, 0.68-0.89). The ROC area for calprotectin was significantly greater than the corresponding ROC areas for WBC (P < 0.001) and PCT (P = 0.02) but only marginally better than the ROC area for CRP (0.71; 95% CI, 0.68-0.89).

Conclusion: Plasma calprotectin appears to be a useful early marker of bacterial infections in critically ill patients, with better predictive characteristics than WBC and PCT.

MeSH terms

  • Adult
  • Aged
  • Bacterial Infections / diagnosis
  • Bacterial Infections / epidemiology
  • Bacterial Infections / metabolism*
  • Biomarkers / metabolism
  • C-Reactive Protein / metabolism
  • Calcitonin / metabolism*
  • Cohort Studies
  • Critical Illness*
  • Early Diagnosis
  • Female
  • Humans
  • Intensive Care Units
  • Leukocyte Count
  • Leukocyte L1 Antigen Complex / metabolism*
  • Logistic Models
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Organ Dysfunction Scores
  • ROC Curve
  • Risk Assessment
  • Severity of Illness Index
  • Sweden


  • Biomarkers
  • Leukocyte L1 Antigen Complex
  • Calcitonin
  • C-Reactive Protein