Existing guidelines’ recommendations for vascular access planning are mainly based on glomerular filtration rate (eGFR) changes. With “optimal timing for vascular access referral and placement” often “debatable”, however, the authors of new research published in the Journal of Vascular Access (JVA) say that a more refined tool is needed to carry out the best possible planning of vascular access creation for haemodialysis. That is where the kidney failure risk equation (KFRE), which the study sought to evaluate, comes in.
“Predicting the risk of progression to kidney replacement therapy (KRT) is challenging as the pattern of decline of kidney function is variable between patients,” say the study’s authors, among them lead author Bernardo Marques da Silva (Centro Hospitalar Universitário Lisboa Norte, Lisbon, Portugal). Initiating dialysis before it is necessary has not been shown, they argue, to improve outcomes—and it is therefore important to time it correctly by anticipating eGFR decline according to a number of risk factors.
The KFRE, which the authors say has been “widely validated in various populations”, has been in use since 2011 and was developed by Navdeep Tangri (University of Manitoba, Winnipeg, Canada) et al. What Marques da Silva et al sought to ascertain in their study is the KFRE’s utility for predicting the best time to create a vascular access.
Their study was a retrospective, single-centre analysis of chronic kidney disease (CKD) patients between January 2018 and December 2019. Included patients, who numbered 256, were those who had been referred for haemodialysis access creation. Patients already on haemodialysis treatment, or who had received previous kidney replacement therapy (KRT) such as peritoneal dialysis or a kidney transplant, were excluded from the study, as were patients lost to follow-up and those who had an existing vascular access or no quantifiable proteinuria at time of referral.
Primary outcomes for the study were KRT start and mortality, the authors detail. Other outcomes included vascular access placement, primary failure of vascular access, and timing of placement relative to referral. The mean age of patients was 70.4±12.9 years and 64.5% were male.
Of the included patients, 62.1% required KRT. The KFRE at referral for vascular access creation “accurately predicted progression to start of KRT with an area under receiver operating characteristic curve (auROC) of 0.788, a sensitivity of 72.8%, and specificity of 78.4% with a cut-off of 20%”. It predicted KRT start within two years (38.3±23.8% vs 17.6±20.9%, p<0.001; hazard ratio [HR] 1.05; 95% CI 1.06–1.12; p<0.001).
“In our cohort,” the authors explain, “mean time from vascular access consult to KRT initiation was 12.5±10.4 months and 50.9% of patients had a usable AVF/AVG at dialysis initiation.” This, they suggest, reflects “a high percentage of primary failure rate or vascular access creation close to KRT start”, which fails to allow for “adequate maturation”.
Marques da Silva et al argue that their study has a number of advantages, among them the relatively advanced CKD of its cohort, meaning that its finding of reliability for the KFRE “is still reliable for lower eGFR”. They state that they were also “able to identify a KFRE cut-off that allows to establish an optimal six-month period for vascular access creation and maturation”.
They conclude that their findings demonstrate that the two-year KFRE “can be a useful tool when planning timing for vascular access creation”. They add that they show that a KFRE ⩾20% can be used “in addition to eGFR when referring patients for vascular access planning and help to establish higher priority patients for VA placement”. Marques da Silva and colleagues’ final recommendation is that referral for vascular access should take place when eGFR is <20mL/min/1.73m2 and KFRE is ⩾20%.
