Value of calcium-phosphorus product and CONUT score in predicting postoperative re-failure of autologous arteriovenous fistula dysfunction

Objective To explore the value of calcium-phosphorus product and nutritional control status（CONUT） score in predicting postoperative re-failure of autologous arteriovenous fistula（AVF） dysfunction.

Methods  Clinical data were reviewed for 112 AVF patients undergoing internal fistula repair/reconstruction from June 2019 to May 2021. After 12-month follow-ups, they were assigned into two groups of patency（n=68） and re-failure（n=32） according to the occurrence of postoperative re-failure. The inter-group differences were compared in clinical profiles, calcium-phosphorus product and CONUT score. Logistic regression analysis was performed for identifying the risk factors for postoperative re-failure. The value of calcium-phosphorus product and CONUT score was examined in predicting re-failure by receiver operating characteristic（ROC） curve. Based upon the optimal stage as a grouping basis, Kaplan-Meier（K-M） method was employed for examining the survival of postoperative internal fistula in patient groups of different calcium and phosphorus products and CONUT scores.

Results  The products of calcium and phosphorus and the proportions of diabetes mellitus in re-failure group were higher than those in patency group（51.78 ± 9.88） vs （43.32 ± 6.95）, 50.00% vs 25.00%, P＜0.05. The CONUT score was higher in re-failure group than that in patency group（P＜0.05）. Statistically significant inter-group difference existed in the distribution of CONUT scores（P＜0.05）. Logistic regression analysis revealed that diabetes mellitus, calcium-phosphorus product, mild malnutrition and moderate-to-severe malnutrition in COUNT score were independent risk factors for AVF dysfunction post-operation（P＜0.05）. ROC curve analysis indicated that the optimal cut-off values of calcium-phosphorus product and CONUT score for predicting re-failure after AVF dysfunction were ＞4751 mg²/L² and ＞1 point respectively, area under the curve（AUC）（95%CI） was 0.781（0.687-0.857）, 0.778（0.684-0.855） and AUC（95%CI） of calcium-phosphorus product plus CONUT score was 0.824（0.735-0.893）. It was better than the predictive power of the two alone（P＜0.05）. Based upon the optimal cut-off value, K-M survival analysis indicated that survival curve of postoperative internal fistula was better in high calcium and phosphorus product group than that in low calcium and phosphorus product group; survival curve of postoperative internal fistula was better in low COUNT score group than that in high COUNT score group（P＜0.05）.

Conclusion  Calcium-phosphorus product and CONUT score are risk factors for postoperative re-failure of AVF dysfunction. Both affect the survival time of postoperative internal fistula and may serve as reference parameters for predicting postoperative internal fistula re-failure.