Abstract

Background: Prior nonrandomised studies have suggested nephroprotective effects of arteriovenous fistula (AVF) formation, but these are plausibly susceptible to immortal time and selection biases. Methods: We studied patients attending nephrology clinics in the West of Scotland during 2010-2022 with an eGFR ≤15mL/min/1.73m2 and no prior AVF. Using target trial emulation and a sequential trial design, we simulated a hypothetical trial that would randomise patients to either undergo AVF formation immediately or not to undergo AVF formation. The primary outcome was the difference in eGFR slope for the first six months of follow-up, estimated using a mixed-effects model. The secondary outcomes were 5-year absolute risks of dialysis and death, estimated using the Aalen-Johansen and Kaplan-Meier estimators respectively. Results: 1,364 unique patients (mean age 51.1, 55.7% male) contributed 3,125 person-trials, with 561 in the AVF and 2,564 in the no AVF group. Mean eGFR was 12.6mL/min/1.73m2 and the median number of eGFR measurements per person-trial was 7 (IQR 4 – 12). Slope of eGFR decline did not differ significantly between the AVF and no AVF groups (between group difference -0.67mL/min/1.73m2/year, 95%CI -1.43, 0.10). The 5-year absolute risk of dialysis was 87% (95%CI 84, 91) in the AVF group and 75% (95%CI 73, 77) in the no AVF group and the 5-year survival probability was 77% (95%CI 70, 83) in the AVF group and 67% (95%CI 64, 69) in the no AVF group. Conclusions: In this study of patients with advanced CKD, there was no evidence of a nephroprotective effect of AVF formation.