Clinical impact of the Kidney Failure Risk Equation for vascular access planning

Abstract

Background: Risk-based thresholds for arteriovenous (AV) access creation has been proposed to aid vascular access planning. We aimed to assess the clinical impact of implementing the Kidney Failure Risk Equation (KFRE) for vascular access referral.

Methods: A total of 16 102 nephrology-referred chronic kidney disease (CKD) patients from the Swedish Renal Registry 2008-18 were included. The KFRE was calculated repeatedly, and the timing was identified for when the KFRE risk exceeded several pre-defined thresholds and/or the estimated glomerular filtration rate was <15 mL/min/1.73 m2 (eGFR15). To assess the utility of the KFRE/eGFR thresholds, cumulative incidence curves of kidney replacement therapy (KRT) or death, and decision-curve analyses were computed at 6 and 12 months, and 2 years. The potential impact of using the different thresholds was illustrated by an example from the Swedish access registry.

Results: The 12-month specificity for KRT initiation was highest for KFRE >50% {94.5 [95% confidence interval (CI) 94.3-94.7]} followed by KFRE >40% [90.0 (95% CI 89.7-90.3)], while sensitivity was highest for KFRE >30% [79.3 (95% CI 78.2-80.3)] and eGFR <15 mL/min/1.73 m2 [81.2 (95% CI 80.2-82.2)]. The 2-year positive predictive value was 71.5 (95% CI 70.2-72.8), 61.7 (95% CI 60.4-63.0) and 47.2 (95% CI 46.1-48.3) for KFRE >50%, KFRE >40% and eGFR <15, respectively. Decision curve analyses suggested the largest net benefit for KFRE >40% over 2 years and KFRE >50% over 12 months when it is important to avoid the harm of possibly unnecessary surgery. In Sweden, 54% of nephrology-referred patients started hemodialysis in a central venous catheter (CVC), of whom only 5% had AV access surgery >6 months before initiation. Sixty percent of the CVC patients exceeded KFRE >40% a median of 0.8 years (interquartile range 0.4-1.5) before KRT initiation.

Conclusions: The utility of using KFRE >40% and KFRE >50% is higher compared with the more traditionally used eGFR threshold <15 mL/min/1.73 m2 for vascular access planning.

Keywords: CKD; arteriovenous fistula; epidemiology; haemodialysis; vascular access.

Figure 1:

(A–D) Cumulative incidence plots by different decision thresholds.

Figure 2:

(A, B) DCA for the utility of the 2-year KFRE versus eGFR below 15 mL/min/1.73 m².

Figure 3:

(A, B) Harm/benefit ratio for different decision measures. A threshold probability of 10% represents an odds of 1:9. The interpretation of the odds 1:9 in the context of vascular access surgery is that the patient and doctor consider a failing to place an AV access on time 9 times worse than doing unnecessary vascular access surgery. The odds of 1:1 means that the patient and doctor consider receiving an unnecessary AV access as bad as missing KRT in a timely AV access.

Figure 4:

KFRE up to 5 years before initiation of hemodialysis.