Background and Aims: Stent placement has been widely applied for the treatment of arteriosclerosis obliterans of lower extremities. However, the incidence of postoperative femoropopliteal in-stent restenosis (ISR) remains a difficult clinical problem. Studies have demonstrated that ISR is closely associated with the nutritional and inflammatory markers, and the availability of reliable predictive factors for ISR after lower extremity arterial stenting is of great clinical value. Therefore, this study was conducted to investigate the value of C-reactive protein (CRP)/albumin ratio (CAR) in prediction of ISR and its severity after lower extremity artery stenting. 
Methods: The clinical data of 186 patients undergoing lower limb artery stenting in the First Affiliated Hospital of Jinzhou Medical University from January 2017 to May 2019 were retrospectively collected. The occurrence of ISR within 12 months after operation as well as the severity of ISR were analyzed. The influencing factors for ISR were determined by univariate and multivariate Logistic regression analysis, and the predictive abilities of CAR, CRP and albumin for ISR and its severity were evaluated by ROC curve analysis 
Results: During a follow-up period for 12-month, ISR occurred in 54 patients (29.0%), of whom, 24 cases had a severe disease (ISR>75%). In patients with ISR, the numbers of male, smoking and diabetes cases as well as the values of CRP and CAR were higher, and the values of albumin and ankle-brachial index (ABI) were lower than those in patients without ISR (all P<0.05). The results of multivariate regression analysis showed that male sex (P=0.023), having diabetes (P=0.002), smoking (P=0.023), low albumin (P=0.007) and high CRP (P<0.001) were independent risk factors for ISR after lower extremity artery stenting. The area under the curve (AUC) of CAR for predicting ISR was 0.846, which was superior to that of CRP (AUC=0.835) and albumin (AUC=0.822), where the optimal cutoff value was 0.6, with the sensitivity and specificity 70.4% and 87.2%, respectively. The AUC of CAR for predicting the severity of ISR was 0.662, which was better than that of CRP (AUC=0.646) and albumin (AUC=0.630), where the optimal cutoff value was 1.066, with the sensitivity and specificity of 75% and 42.4%, respectively. 
Conclusion: CAR can be used for early prediction of ISR and the severity of ISR in patients undergoing lower extremity artery stenting, which is more accurate than that of CRP or albumin alone. The value of CAR>0.6 suggests that the risk of ISR may be increased, and CAR>1.06 suggests that the severity of may be exacerbated.