Elevated C-reactive protein levels at ICU discharge as a predictor of ICU outcome: a retrospective cohort study

BACKGROUND Before discharging a patient from the ICU, an adequate patient evaluation is needed to detect individuals as high risk for unfavorable outcome. A pro- or anti-inflammatory status is a potential risk factor for an adverse outcome, and elevated CRP concentrations have shown to correlate with organ failure. Several studies have been performed to evaluate the use of CRP as a marker of post-ICU prognosis. Results are seemingly conflicting, and it is worthwhile to investigate these markers further as CRP is an adequate marker of pro- and anti-inflammatory status of the patient. We aimed to test the hypothesis that elevated CRP levels at ICU discharge are associated with an increased risk of ICU readmission and in-hospital mortality in patients with a prolonged ICU stay. METHODS A retrospective cohort study was performed in a single-center hospital with an 18-bed mixed medical/surgical ICU. Patients discharged alive from the ICU with at least 48-h ICU length of stay were evaluated. Patients were distributed into two groups: 'high CRP' (≥75 mg/L) and 'low CRP' (<75 mg/L) at ICU discharge. We assessed the difference in adverse outcome (ICU readmission and/or in-hospital mortality) between these groups. RESULTS A total of 998 patients were included. Compared to the 'low CRP' group, patients in the 'high CRP' group had a higher readmission rate (13.1 vs. 7.4 %; p = 0.003). The post-ICU mortality rate in the 'high CRP' group and 'low CRP' group was 6.9 % and 4.7 %, respectively; p = 0.127. Combined readmission and mortality rates were significantly higher in the 'high CRP' group in comparison with the 'low CRP' group (17.9 vs. 10.1 %; p = 0.001). Hospital mortality in patients readmitted to the ICU was significantly higher than in non-readmitted patients (20 vs. 4.3 %; p < 0.001). Strikingly, the 'high CRP' group had significantly lower APACHE II and SOFA scores at ICU admission compared to the 'low CRP' group. This highlights the potential for ICU-acquired risk factors, including CRP. CONCLUSIONS A high CRP concentration (≥75 mg/L) within 24 h before ICU discharge is associated with an increased risk of adverse outcome post-ICU discharge. However, CRP at discharge represents only a very moderate risk factor and may not be used for individual clinical decision-making.