Tweet

Joel M. Topf, MD FACP

9 Dec, 10 tweets, 4 min read

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

In the 1980's the hot idea in nephrology was low protein diets to preserve GFR. The NIH funded a Big Science study to test the theory, the Modification of Diet in Renal Disease study, MDRD. The study was a mess and fell on its face, but they did collect a lot of cool data! 2/10

Among that data was iothalamate clearances which are a really good approximation of GFR. So Andy Levey and friends took those data and combined it with age, gender, and race to come up with the MDRD formula. 3/10

This was the original sin, the place where nephrology started to use race to calculate eGFR. Why did they do it? You can see the from the data that Black people (open circles) tended to have higher Cr for the same GFR. 4/10

And just a year earlier a study had been published showing black people had higher serum creatinine than white people. This study had no idea what people's GFRs were. They just found higher creatinine in Black people. 5/10

MDRD had other problems. It underestimated kidney function in people without kidney disease. This was a big problem when screening people to be kidney donors. It also had few black people and even fewer people with diabetes (and zero people on insulin) 6/10

But the equation business was a good racket and in 2009 Level and Co came back with the CKD-EPI formula which corrected or improved many of the problems with MDRD. 7/10

CKD-EPI is way more complex than previous formulas. It includes a technique called a knot to allow it to change the slope at low creatinines to try to improve accuracy at high GFRs. 8/10

You can see the effect of the knot here, note the decreased bias at GFRs over 60 9/10

With the larger number of Black people the race adjustment shrank by about a quarter from 21% to 16%. Up until September of 2021 this was the formula people were supposed to use but a survey of clinical labs in 2019 found that 60% still used MDRD! 10/10

• • •

Missing some Tweet in this thread? You can try to force a refresh

This Thread may be Removed Anytime!

Twitter may remove this content at anytime! Save it as PDF for later use!

More from @kidney_boy

Joel M. Topf, MD FACP

@kidney_boy

10 Dec

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

Use of race in eGFR is doesn't work because race is a social construct. “A person who could be categorized as black in the United States might be considered white in Brazil or colored in South Africa” Racial identity shifts with experience and time. 2/10 nytimes.com/roomfordebate/…

I spoke Danish at home. I ate Danish food. At Christmas we danced around the Christmas tree singing Danish carols. But when I went outside my home, I was black. nytimes.com/roomfordebate/… 3/10

Read 11 tweets

Joel M. Topf, MD FACP

@kidney_boy

9 Dec

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

Read 11 tweets

Joel M. Topf, MD FACP

@kidney_boy

8 Dec

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

To understand how nephrology got itself into this eGFR and race mess I want to unpack what is going on in the equations. What are they trying to do and how do they work. 2/10

Estimated GFR depends on people being in steady state. Steady state means the Day 1 creatinine = Day 2 creatinine = Day X creatinine. It doesn't matter if the cr is 0.6 or 4.4, as long as the cr is roughly the same from day to day they are in steady state. 3/10

Read 11 tweets

Joel M. Topf, MD FACP

@kidney_boy

8 Dec

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

My parents grew up in the segregated south and tell me stories of toe curling segregation. They are embarrassed to say that at the time, it seemed normal. 2/10

What are we doing today that we will look back at as being unconscionably racist?

I think we will look at the two separate GFRs listed on a routine BMP like the two drinking fountains. 3/10

Read 10 tweets

Joel M. Topf, MD FACP

@kidney_boy

2 Dec

More fellows find NephJC to be “very effective” than:
CJASN, NephSAP, JASN, textbooks, KDIGO, AJKD, journals, RFN, and more. Wow. Just wow. asn.apprisor.org/epsAbstractASN…