Thread by @kidney_boy

I am going to try to recap my recent grand rounds on race and GFR in a few #tweetorials. Here is the fourth one. You can find the presentation files and a video of me presenting at pbfluids.com/2021/12/the-ne………… 1/10

So both MDRD and CKD-EPI found that Black Americans had a higher GFR (on average) for the same creatinine compared to White Americans. Also NHANES showed that Black people have higher creatinines than White people. Why? ajkd.org/article/S0272-… 2/10

Looking at non-creatinine determinants of GFR there are a limited number of variables. Though I included "metabolism" that only comes in play at high serum creatinine so that can't be the factor here.

Increased production from increased muscle mass was the prime suspect. 3/10

In the 1999 MDRD study, Levey et al. presumed that the increased GFR in Black Americans was due to increased muscle mass. They provided 3 references for this and they are a clown show 🤡 4/10

Black people having Increased muscle mass is a longtime racial stereotype that was largely accepted by medicine. But when people did question this it doesn't hold up.

Looking at serum Cr can be difficult because it is confounded by GFR, so Hsu et al looked at anuric dialysis patients and found here, with a GFR of zero, Black people still had higher serum Cr, and surprisingly, adjusting for muscle mass DID NOT eliminate the differences!😮 5/10

Levey and Co did an analysis to see if they could remove race from the GFR equations by replacing it with height and weight, presuming that if race was a proxy for size, this would work pretty well. Nope. Adding height and weight did not account for the differences. 6/10

So we know that Black people in our study samples have high GFR for the same Cr but we don't know why. I think it is diet but GI excretion is possible. Tubular secretion falls down because of anuric dialysis studies

But we really don't know and we should investigate this 7/10

Despite not knowing why it performs this way, eGFR provides a signal of increased health in a group of people who have worse kidney outcomes. This is perverse. 8/10

Anyone who has visited a few dialysis units in the US can't avoid noticing the racial disparity. Black Americans face almost 3 times the incidence of ESKD as White people. 9/10

But what is less well known is that the prevalence of CKD is almost the same

Black Americans: 16%
White Americans 15.7%

Despite the same rate of CKD Black people reach ESKD 3x more often. Delaying diagnosis in this group is counter to any sane public health policy. 10/10