Author Interviews, Biomarkers, Gender Differences, Kidney Disease, NEJM, Race/Ethnic Diversity / 26.01.2023 Interview with: Prof. dr. Hans Pottel KU Leuven Kulak Department of Public Health and Primary Care Belgium What is the background for this study? Response:  The glomerular filtration rate (GFR) is used to diagnose patients with chronic kidney disease and is also used to adjust the dose of drugs that are eliminated by the kidneys. An accurate estimation of GFR is considered of importance in the management of kidney health in patients. In 2021 we published a new serum creatinine based equation, called the European Kidney Function Consortium (EKFC) equation (Pottel H. et al, Development and Validation of a Modified Full Age Spectrum Creatinine-Based Equation to Estimate Glomerular Filtration Rate : A Cross-sectional Analysis of Pooled Data. Ann Intern Med (2021) 174: 183-191): EKFC-eGFR = 107.3 / [Biomarker/Q]a x [0.990(Age – 40) if age > 40 years] With a = 0.322 if Biomarker/Q is less than 1, and a = 1.132 if Biomarker/Q is 1 or more. The equation can easily be interpreted: the leading coefficient equals the glomerular filtration rate (GFR) of 107.3 mL/min/1.73m², which is the average GFR in healthy children (aged > 2 years), adolescents and young adults. The average healthy GFR remains constant until the age of 40 years, and starts decreasing beyond that age. The GFR is inversely related to the ‘rescaled’ biomarker. The rescaling factor (Q) is the average biomarker value for healthy people of a specific population (e.g. children, adult men, adult women, white people, black people, …). Biomarker/Q equals ‘1’ for the average healthy person, corresponding with eGFR = 107.3 mL/min/1.73m² (up to 40 years of age). It should be noted that for serum creatinine, the Q-value depends on sex and race. Our hypothesis was that the above equation is valid for any renal biomarker, on the condition that the biomarker is appropriately scaled. We showed that the same equation was able to estimate GFR from 2 years to oldest ages. In the current study we tested and validated our hypothesis by applying the above formula for appropriately ‘rescaled’ cystatin C. (more…)
Author Interviews, Kidney Disease / 16.10.2020 Interview with: Mallika Mendu, MD, MBA MedicalDirector of Clinical Operations Brigham and Women’s Hospital What is the background for this study? What are the main findings? Response: African-Americans with chronic kidney disease have poorer outcomes with respect to hypertension control, timely nephrology referral, progression to end stage renal disease, placement of vascular access and transplantation compared to other racial groups. For the past two decades a race multiplier has been applied in equations that estimate glomerular filtration rate (a proxy for kidney function) for African-Americans. We sought to determine whether what the impact of the race multiplier term was on care delivered to African-Americans, by using our health system-wide CKD registry. We were particularly focused on advanced CKD patient outcomes, knowing that there are health disparities that could be potentially exacerbated.

The original CKD-EPI and MDRD studies showed an association between African-American race with higher measured GFR at the same blood creatinine concentration. However, there have been concerns raised about the application of the race multiplier to all African-American patients. First, there is no clear biological explanation for the association, the identification of Black race was unclear in some of the cohorts used in these studies, and there is vast genetic and ancestral heterogeneity among those who self-identify as black. The use of the race multiplier also ignores the fact that race is a social, not biological construct.

We found that with the removal of the race multiplier, up to one in every three African-American patients would be reclassified as having a more severe stage of CKD, with one-quarter of African-American patients going from stage 3 to stage 4. We also found that with the removal of the race multiplier, 64 patients would have had an eGFR <20, the threshold for referral for kidney transplant, and none of these patients were referred, evaluated or waitlisted for transplant. This is in contrast, to those African-American patients with an eGFR <20 with the race multiplier applied, who had a higher odds of being referred, evaluated or waitlisted for transplant compared to other racial groups (Odds ratio of 2.28, compared to White cohort).

Author Interviews, Geriatrics, Kidney Disease / 05.05.2019 Interview with: Dr. Luciano da Silva Selistre MD MS PhD Professor de Medicina - UCS What is the background for this study? What are the main findings? Response:   We have found that no equation for estimating renal function in the elderly is fully accurate. There are important mistakes between them. (more…)