Standard Chronic Kidney Disease Tests are Not Precise for African Americans and We Need to do Better

Here’s a shocking fact for you- individuals don’t always conform to averages.

Despite this, we use averages as an analysis for so many things. As it documents the majority, its correct for the majority of people.

But when it comes to healthcare- treating the majority means those who are in the minority may not receive the care that they direly need.

We need to make a change on how we investigate averages in healthcare. One of the starking examples of this is Chronic Kidney Disease (CKD).

How Kidney Function is Tested

The most common way to test the function of someones kidneys is to investigate the levels of creatinine in the blood. This chemical should be filtered out by the kidneys. Therefore a high level of creatinine in the blood means that the kidneys aren’t functioning well.

The problem with this measurement is that creatine is produced by the muscles. That means that those who have a higher muscle mass will naturally have higher levels of creatinine. So, doctors came up with a sort of equation to help account for this and other factors.

This equation is called CKD-EPI. It produces a number on a 0 to 120 scale. A score of 0 indicates little to no filtering is occurring. A score of 120 means the kidneys are filtering perfectly. Since older people and women tend to have less muscle (on average of course), this equation raises their results. Similarly, because African Americans tend to have more muscle, their estimated glomerular filtration rate, or eGFR is raised by 15.9%.

This formula is used widely to assess kidney function. It’s become the standard because its effective for the “average patient.”

However, there’s an issue. Because despite the fact that African Americans tend to produce higher scores with this formula, they are actually more likely to face reduced function of their kidneys than white Americans.

Contrasting Opinions

The problem became abundantly clear to Carmen Peralta after a mixed-race patient came to her office to ask whether his first or second kidney test score was accurate. One indicated that his baseline kidney function was normal while the other indicated an issue. This discrepancy was because of test results which tried to account for his muscle mass.

Michael Shlipak is the head of the Kidney Health Research Collaborative. He too says that this standard test is too imprecise when it comes to race. Shlipak is also on the board of Kidney Disease: Improving Global Outcomes. This is a group of Nephrologists who are dedicated to improving experiences for CKD patients globally. This group is working to draft new international guidelines for CKD. Included in these will be an alternative test which uses cystatin C. This protein is less affected by muscle mass and so it can produce more accurate results. Currently, this type of test is utilized when the creatinine tests are inconclusive.

The fact of the matter is the eGFR is too imprecise. Its estimated that this type of tests leads to “shaky results” in approximately 1/3 of patients. This is because shocker- individuals don’t conform to averages.

A diagnosis when you don’t actually have the disease causes unnecessary stress and the use of medications that may not be necessary. Underdiagnosis leads to incorrect treatment and worse outcomes.

 The test had good intentions but-

“It exacerbates problems African Americans already face in getting quality care.”

The Problems Already Present

African American CKD patients face many more challenges than white CKD patients in general. African Americans have a higher risk of hypertension, obesity, and diabetes which are all risk factors for CKD.  The issues with the eGFR means that in addition to issues with care, African American patients face inequities before they even know their risk of kidney disease

A small difference in estimated kidney function can mean the difference between two completely different treatment regimes. It can mean not getting on the transplant list as quickly, delayed dialysis treatment, or a continuation of medication the patient shouldn’t be on.

A delayed placement on the transplant list is the biggest issue. Especially because there are already fewer African American kidney donors (12.6% of all donors). This means that its hard to find a genetic match for African American CKD patients, resulting in a longer wait period. If it takes them longer to get on the transplant list in the first place, the time till a new kidney is exorbitant.

“The use of kidney function estimating equations that include race as a variable unduly restrict access to care.”

Looking Forward

The eGFR is entrenched as a method. That means we need to work harder to amend it. But the good news is more people are questioning the eGFR and conducting studies to examine its flaws.

The key is research and education. With an increased focus on these two things we may be able to ultimately improve outcomes for patients.

The good thing is that we now know these things are needed. The first step is knowledge. Now we just need to act.   

Receiving the wrong diagnosis can be just as damaging as not being diagnosed when there’s something critically wrong. The essence of medicine is that it works when it is prescribed in the right circumstance. We need to do better for all patients.

You can read more about this issue here.


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