BACKGROUND:To investigate the relationship between the levels of serum complement C1q and the risk and severity of acute ischemic stroke, a total of 154 patients with acute ischemic stroke and 42 healthy volunteers as normal controls were enrolled in the present study. METHODS:According to the onset time of stroke, patients were divided into three groups. Using an immune transmission turbidity method, the levels of serum complement C1q were detected to investigate the relationship between the level of serum complement C1q and the incidence and severity of acute ischemic stroke. The risk factors of these groups were calculated using a conditional logistic regression model. The assessment of neurological function impairment was carried out according to the National Institute of Health Stroke Scale. Then correlation anal- ysis was carried out between the level of serum complement C1q among patients with acute ischemic stroke and the degree of neurological function impairment. RESULTS:The results showed that the level of serum complement C1q was higher in the ischemic stroke group than in the control group. Using a conditional logistic regression model it was discovered that serum complement C1q was the independent pathogenic factor of cerebral infarction. There also was a decreasing trend in the level of serum complement C1q with the extension of the onset time and an increasing trend in the level of serum complement C1q with the increase in the maximum diameter of infarction volume. CONCLUSIONS:Serum complement C1q is an independent risk factor for acute outbreak of ischemic stroke, whose level is closely related to the outbreak and infarct size and neurological function impairment.