High-sensitivity C reactive protein as a predictor of inhospital mortality in patients with cardiovascular disease at an emergency department: a retrospective cohort study

OBJECTIVE: We investigated whether serum high-sensitivity C reactive protein (hs-CRP) levels measured in an emergency department (ED) are associated with inhospital mortality in patients with cardiovascular disease (CVD). DESIGN: A retrospective cohort study. SETTING: ED of a teaching hospital in Japan. PARTICIPANTS: 12 211 patients with CVD aged ≥18 years who presented to the ED by an ambulance between 1 February 2006 and 30 September 2014 were evaluated. MAIN OUTCOME MEASURES: Inhospital mortality. RESULTS: 1156 patients had died. The inhospital mortality increased significantly with the hs-CRP levels (<3.0 mg/L: 7.0%, 95% CI 6.4 to 7.6; 3.1–5.4 mg/L: 9.6%, 95% CI 7.9 to 11.3: 5.5–11.5 mg/L: 11.2%, 95% CI 9.4 to 13.0; 11.6–33.2 mg/L: 12.3%, 95% CI 10.5 to 14.1 and ≥33.3 mg/L: 19.9%, 95% CI 17.6 to 22.2). The age-adjusted and sex-adjusted HR for total mortality was increased significantly in the three ≥5.5 mg/L groups compared with the <3.0 mg/L group (5.5–11.5 mg/L: HR=1.32, 95% CI 1.09 to 1.60, p=0.005; 11.6–33.2 mg/L: HR=1.38, 95% CI 1.14 to 1.65, p=0.001 and ≥33.3 mg/L: HR=2.15, 95% CI 1.84 to 2.51, p<0.001). Similar findings were observed for the CVD subtypes of acute myocardial infarction, heart failure, cerebral infarction and intracerebral haemorrhage. This association remained unchanged even after adjustment for age, sex and white cell count and withstood Bonferroni adjustment for multiple testing. When the causes of death were divided into primary CVD and non-CVD deaths, the association between initial hs-CRP levels and mortality remained significant, but the influence of hs-CRP levels was greater in non-CVD deaths than CVD deaths. The percentage of non-CVD deaths increased with hs-CRP levels; among the patients with hs-CRP levels ≥33.3 mg/L, non-CVD deaths accounted for 37.5% of total deaths. CONCLUSION: Our findings suggest that increased hs-CRP is a significant risk factor for inhospital mortality among patients with CVD in an ED. Particular attention should be given to our finding that non-CVD death is a major cause of death among patients with CVD with higher hs-CRP levels.