Plasma C3 and C3a Levels in Cryptogenic and Large-Vessel Disease Stroke: Associations with Outcome

Abstract

BACKGROUND AND PURPOSE: Inflammation seems to be a key player in the pathophysiology of stroke. In this study, we compared plasma C3 and C3a levels in cryptogenic and large-vessel disease (LVD) subtypes of ischemic stroke and control subjects and evaluated their association to outcome at 3 months and 2 years. METHODS: C3 and C3a levels in plasma of 79 cryptogenic stroke and 73 LVD stroke patients, sampled within 10 days and at 3 months after stroke, and age- and sex-matched control subjects from the Sahlgrenska Academy Study on Ischemic Stroke were measured by ELISA. Functional outcome was assessed with the modified Rankin Scale. RESULTS: Plasma C3 was increased in both stroke groups at both time points. Systemic elevation of C3a was limited to the acute phase in the cryptogenic stroke group, whereas plasma C3a levels in the LVD group were also elevated at the 3-month follow-up. In the LVD group, plasma C3 levels in the upper third at the 3-month follow-up were associated with an unfavorable outcome after 3 months independently of age and sex: odds ratio (OR) 5.56; 95% confidence interval (CI) 1.03-29.93; p = 0.045; as well as after 2 years: OR 4.75; 95% CI 1.11-20.30; p = 0.036. In the cryptogenic stroke group, high plasma C3a levels in the acute phase were associated with an unfavorable outcome after 3 months: OR 3.75; 95% CI 1.01-13.96; p = 0.049 in univariate analysis but not after adjustment for age and sex (p = 0.050). CONCLUSIONS: Plasma C3 and C3a levels are elevated in cryptogenic and LVD stroke and the predictive value of these markers may depend on stroke subtype. Further studies on the role of the complement system in ischemic stroke outcome based on larger patient populations and controlling for the effect of infections, are clearly warranted.