Measuring both procalcitonin and C-reactive protein for a diagnosis of sepsis in critically ill patients

Abstract

Background: The usefulness of procalcitonin (PCT) and C-reactive protein (CRP) as individual biomarkers, and in combination, for the identification of infections in a critically ill patient cohort was evaluated retrospectively.

Methods: Best cut-off values for PCT and CRP for a diagnosis of sepsis in critically ill patients were determined using receiver operator characteristic (ROC) curve analysis. Both combined tests and individual tests were performed for PCT and CRP, with positive and negative results recorded, and accuracy evaluated using odds ratios (OR).

Results: In the 55 critically ill patients studied, the best cut-off value for PCT for a diagnosis of sepsis was 1.1 ng/ml (sensitivity, specificity and negative predictive values [NPV] were 82%, 68% and 71%, respectively). In addition, the best cut-off value for CRP was 50.7 mg/l ( sensitivity, specificity and NPV of 90%, 68% and 83%, respectively). Measuring PCT and CRP in combination provided a sensitivity of 79%, a specificity of 86%, and a positive predictive value (PPV) of 90%. Diagnostic OR for the combination of biomarkers versus CRP alone (19 and 18, respectively) were greater than that for PCT (9).

Conclusion: For critically ill patients, CRP and CRP in combination with PCT were found to be suitable biomarkers for diagnosing sepsis, based on their NPV and PPV.

Keywords: Biomarker; C-reactive protein; NPV; PPV; combination; procalcitonin; sensitivity; sepsis; specificity.