In this episode, I’ll discuss why the NKF says its OK to use race-free eGFR to make renal dose adjustments.
A Consensus workgroup of the National Kidney Foundation has just published in the American Journal of Health-System Pharmacy a consensus document title Moving forward from Cockcroft-Gault creatinine clearance to race-free estimated glomerular filtration rate to improve medication-related decision-making in adults across healthcare settings.
In this article, the authors detail how the race-free eGFR formulas published by NKF in 2021 that use either creatinine, cystatin-C or both give a more precise estimate of kidney function than the Cockcroft-Gault formula. The authors also explain why they recommend adjustment of the eGFR value using body surface area to lessen the chance of an inaccurate eGFR estimate in underweight and overweight patients.
But the biggest change for pharmacists that the NKF is recommending is to use these 2021 eGFR formulas to base renal dose adjustment decisions on.
This is a significant change to everyday practice, and implementing it at an individual hospital level will require the consensus of all pharmacists involved to keep renal dose adjustment decisions consistent.
Anticipating arguments against using these new eGFR formulas for renal dose adjustment decisions, the NKF has detailed their counterpoints to common arguments against this change in practice:
1. Your lab’s creatinine assay is different than the one used to study pharmacokinetics and make the prescribing information’s renal dosing recommendations. Because serum creatinine laboratory assays were not standardized until 2011, the results of previous formulas, including Cockcroft Gault, cannot be generalized to patients today. Essentially, this is because creatinine values in the derivation group would not be similar to those determined by a different laboratory. Additionally because of the long time between initial pharmacokinetic studies and a new drug making it to market, the NKF authors estimate that any medication approved prior to 2018 likely has creatinine clearance recommendations that were based off values from a non-standardized lab test.
2. You’re probably not using the same Cockcroft Gault formula that the manufacturer did when making the prescribing information’s renal dosing recommendations. Most manufacturers used actual body weight in their Cockcroft Gault calculations, but pharmacists routinely make adjustments to this bodyweight to account for overweight and obese patients. Therefore saying “we have to use CG because that is what is in the prescribing information” isn’t a valid argument, because you’re likely not using the same CG formula already.
3. The new eGFR formulas are better predictors of medication clearance than CG. The NKF authors cite 4 studies published in 2023 to justify this statement:
Personally, I don’t think switching formulas is that big of a deal, as renal dose adjustment remains a patient specific risk:benefit decision, and these formulas still don’t calculate GFR, they just estimate it.
Members of my Hospital Pharmacy Academy have access to practical training on understanding these NKF recommendations, how to make renal dose adjustment decisions, and over 200 other practical trainings and resources to help in your practice. To get immediate access go to pharmacyjoe.com/academy.
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