Utility of procalcitonin, C-reactive protein and white blood cells alone and in combination for the prediction of clinical outcomes in community-acquired pneumonia

Background: The added value of biomarkers, such as procalcitonin (PCT), C-reactive protein (CRP), and white blood cells (WBC), as adjuncts to clinical risk scores for predicting the outcome of patients with community-acquired pneumonia (CAP) is in question. We investigated the prognostic accuracy of initial and follow-up levels of inflammatory biomarkers in predicting death and adverse clinical outcomes in a large and well-defined cohort of CAP patients. Methods: We measured PCT, CRP and WBC on days 1, 3, 5, and 7 and followed the patients over 30 days. We applied multivariate regression models and area under the curve (AUC) to investigate associations between these biomarkers, the clinical risk score CURB-65, and clinical outcomes [i.e., death and intensive care unit (ICU) admission]. Results: Of 925 patients with CAP, 50 patients died and 118 patients had an adverse clinical outcome. None of the initial biomarker levels significantly improved the CURB-65 score for mortality prediction. Follow-up biomarker levels showed significant independent association with mortality at days 3, 5, and 7 and with improvements in AUC. Initial PCT and CRP levels were independent prognostic predictors of adverse clinical outcome, and levels of all biomarkers during the course of disease provided additional prognostic information. Conclusions: This study provides robust insights into the added prognostic value of inflammatory markers in CAP. Procalcitonin, CRP, and to a lesser degree WBC provided some prognostic information on CAP outcomes, particularly when considering their kinetics at days 5 and 7 and when looking at adverse clinical outcomes instead of mortality alone.