Supplementary Material for: Higher Levels of Cystatin C Are Associated with Extracranial Carotid Artery Steno-Occlusive Disease in Patients with Noncardioembolic Ischemic Stroke

Background: Large artery atherosclerosis is a major cause of ischemic stroke worldwide. Differential biomarker profiles associated with extra- and intracranial atherosclerosis are a topic of considerable interest. Cystatin C (CysC), a marker of renal function, is a risk factor for cardiovascular disease. Aim: We sought to determine whether CysC levels were associated with extra- and intracranial large artery stenosis (LAS) in patients with acute ischemic stroke. Methods: We retrospectively analyzed data of acute noncardioembolic ischemic stroke patients who were admitted to our stroke center within 5 days from symptom onset. Serum CysC levels were measured using latex agglutination turbidimetric immunoassay. Extra- and intracranial LAS were defined as ≥50% diameter stenosis or occlusion of the relevant internal carotid artery (ICA) and/or middle cerebral artery (MCA) using carotid echography and volume rendering on magnetic resonance angiography. Multivariate logistic analyses were used to assess the association between CysC levels and LAS after adjustment for potential confounders. Results: Of 205 patients (mean age 70.2 years), 76 (37.1%) had LAS. The distribution of LAS was 29 extracranial ICA, 34 intracranial ICA/MCA (8 ICA only, 25 MCA only, 1 ICA+MCA) and 13 tandem stenosis (both extracranial ICA and intracranial ICA/MCA). Levels of CysC were higher in patients with extracranial ICA stenosis than in those with intracranial ICA/MCA stenosis (1.23 ± 0.33 vs. 0.97 ± 0.21 mg/l, p < 0.001). In multivariate analysis, the highest CysC tertile (>1.04 mg/l) was significantly associated with extracranial ICA stenosis (adjusted odds ratio [OR] 5.01, 95% confidence interval [CI] 1.51-16.63, p = 0.009) after adjustment for age, sex, diabetes, chronic kidney disease, current smoking, systolic blood pressure, HDL cholesterol, high-sensitivity C-reactive protein (hs-CRP) and premorbid lipid-lowering drugs use. When CysC was considered as a continuous variable, 1 SD increase in CysC was significantly associated with extracranial ICA stenosis (adjusted OR 3.01, 95% CI 1.58-5.72, p = 0.001). However, there were no significant associations between CysC levels and intracranial ICA/MCA stenosis. In addition, CysC levels showed a weak but statistically significant correlation with hs-CRP levels (r = 0.195, p = 0.021). Using receiver operating characteristic curve analysis, CysC value displayed good performance in discriminating extracranial ICA stenosis (c-statistic 0.79, 95% CI 0.69-0.89, p < 0.001). Conclusions: This preliminary study suggests that higher levels of CysC were independently associated with symptomatic extracranial ICA stenosis, but not with intracranial ICA/MCA stenosis in patients with noncardioembolic stroke. Our findings provide new insights into the link between serum CysC and carotid atherosclerosis.