Elevated Hemolysis Index is associated with higher risk of cardiovascular diseases

OBJECTIVES: In vivo hemolysis is associated with thromboembolism. Although an increased Hemolysis Index (HI) can be due to in vitro as well as in vivo hemolysis, both reflects a more fragile erythrocyte population. We therefore hypothesized that HI above upper reference limit would be associated with an increased risk of cardiovascular disease (CVD).

METHODS: We identified persons with two elevated HI (HI +) from blood samples analyzed at a university hospital laboratory from 2012 to 2017. We compared their risk of CVD with the risk in matched comparators with normal HI and from the general population. HI + persons and comparators were followed from start date (date of the second elevated HI) until the first of the main outcome: CVD, emigration, death, or end of observation time on December 31, 2018.

RESULTS: In 43,102 unique HI + persons, the risk of developing CVD was 40% higher compared with the general population and 13% higher compared with the matched blood sample cohort. HI + was associated with a significantly increased cumulative incidence of both arterial and venous CVD compared with the matched blood sample cohort and the general population (respectively 47 and 14% for arterial CVD; 78 and 24% for venous CVD). Moreover, overall mortality risk was significantly higher in patients with HI + than in the two comparator groups.

CONCLUSIONS: Elevated HI is associated with increased risk of arterial and venous CVD and with increased mortality. Our findings imply that HI may contribute as a CVD risk biomarker.