USRDS tracks the eGFR of patients starting dialysis, and from the mid 90s through the first decade of the 21st century there was a steady increase in the average GFR at the initiation of dialysis.
From Li et al. 2017, Explaining trends and variation in timing of dialysis initiation in the United States.
While the trend began before 1999, I suspect that the introduction and widespread adoption of the MDRD formula, which revealed that older people with relatively modest increases in creatinine had profoundly low GFRs, had a role in this. This recognition was further reinforced when KDOQI introduced the CKD stages in 2001 that called CKD Stage 5, “Kidney Failure” and implied that CKD stage 5 was a synonym for dialysis.
The trend of starting dialysis at earlier and earlier GFRs reversed following the publication of the IDEAL Trial in 2010. IDEAL showed no survival advantage for starting dialysis at a specific GFR compared to waiting for uremic symptoms that forced the patients to start dialysis. Dialysis is not a cosmetic procedure, we only do it when it is essential.
But deciding when to initiate dialysis is not as easy as waiting for a patient to become uremic, because guidelines, based on retrospective data, tell us to avoid central venous catheters and place arteriovenous access for hemodialysis. Grafts are pretty easy because they usually mature and are ready to use in less than a month. Fistulas, on the other hand, take time to mature and often fail to mature at all.
In this RCT of clopidogrel to assist in access maturation, two thirds of all fistulas were deemed inadequate five months after placement. A few more may have matured after that, but I don’t think it is likely and with a patient nearing dialysis, I suspect new plans for an alternative access will be sought out by that time.
So planning for hemodialysis, with a fistula really means trying to predict where a patient will be six in the future. Learning to do this is the art of taking care of patients with advanced CKD. During my career I have repeatedly been surprised by how long patients with advanced CKD can hold off and delay dialysis. Every time these patients come in I would bring up a list of their old GFRs and marvel how long they had been going with a sub-20 ml/min GFR. Often this would stretch for close to a decade. So when Navdeep Tangri published his Kidney Failure Risk Equation (KFRE) I felt validated as it showed that patients with low GFRs avoided dialysis longer than doctors (and patients) expected.
On Wednesday I posted a typical case to twitter and asked people to decide between sending the patient for fistula creation now or to wait. It is the same patient in both polls, but in the first I provided the eGFR, while in the second I provided the KFRE result.
Same patient; wildly different results. I think it does a nice job of showing that people underestimate patients’ prognosis when they look at eGFR. I find I use the KFRE when talking with patients all the time. It helps reassure people with good kidney function when they are first diagnosed with kidney disease and it helps me when they have advanced CKD when trying to figure out the timing of access procedures and more detailed discussions of end-stage kidney disease.
I use QxMD to calculate the four variable KFRE
This web app by Amarnath Marthi allows you to play with the variables in nearly real time to get an idea of how the equation works (though I wished it would let me use mg albumin / g creatinine). Note that the risk of ESRD goes down as the patient’s age goes up. This is due to the competing risk of death becoming larger with advancing age.
Below are links to some of the great tweets that emerged from these posts. It always amazes me the breadth and depth of knowledge I find in my Twitter feed.