BACKGROUND: C-reactive protein (CRP) is a well-known acute phase protein used to monitor the patient's response during treatment in infectious diseases. Mortality from Community-acquired Pneumonia (CAP) remains high, particularly in hospitalized patients. Better risk prediction during hospitalization could improve management and ultimately reduce mortality levels. The aim of this study was to evaluate CRP on the 3rd day (CRP3) of hospitalization as a predictor for 30 days mortality.

METHODS: A retrospective multicentre cohort study of adult patients admitted with CAP at three Danish hospitals. Predictive associations of CRP3 (absolute levels and relative decline) and 30 days mortality were analysed using receiver operating characteristics and logistic regression.

RESULTS: Eight hundred and fourteen patients were included and 90 (11%) died within 30 days. The area under the curve for CRP3 level and decline for predicting 30 days mortality were 0.64 (0.57-0.70) and 0.71 (0.65-0.76). Risk of death was increased in patients with CRP3 level >75 mg/l (OR 2.44; 95%CI 1.36-4.37) and in patients with a CRP3 decline <50% (OR 4.25; 95%CI 2.30-7.83). In the multivariate analysis, the highest mortality risk was seen in patients who failed to decline by 50%, irrespective of the actual level of CRP (OR 7.8; 95%CI 3.2-19.3). Mortality risk increased significantly according to CRP decline for all strata of CURB-65 score.

CONCLUSIONS: CRP responses day 3 is a valuable predictor of 30 days mortality in hospitalized CAP patients. Failure to decline in CRP was associated with a poor prognosis irrespective of the actual level of CRP or CURB-65.