SGIM Forum

Medical Education

Can Math Be Racist? A Review of the Systemic Racism Inherent in eGFR and PFT Calculations

Dr. Leisman (; Twitter: @stacileisman) is an associate professor of medicine, nephrology and medical education at the Icahn School of Medicine at Mount Sinai. Dr. Karani (; Twitter: @docrck) is the senior associate dean for UME and curricular affairs; the director of the Institute for Medical Education, and a professor of medical education, medicine and geriatrics and palliative medicine at the Icahn School of Medicine at Mount Sinai.

Systemic, or institutionalized, racism occurs when resources are distributed and practices are enacted that benefit white people at the expense of people of color. Effects of these policies disadvantage certain racial or ethnic groups while advancing whites. Two commonly used markers of organ function, estimated glomerular filtration rate (eGFR) and pulmonary function tests (PFTs), contain a race-based correction factor. These correction factors, ostensibly designed to make the calculations more accurate, perpetuate systemic racism.1

Various formulae for estimating a patient’s GFR have been developed to quickly determine patients’ degree of kidney function and ensure appropriate medication dosing. The widely employed Modification of Diet in Renal Disease (MDRD) formula uses serum creatinine, age, sex and what is termed “ethnicity” to calculate a patient’s eGFR.2 It is this value that appears as “eGFR Non-African American” and “eGFR African-American” on most American laboratory test results and provides the basis for the diagnosis and treatment of kidney disease.

At first glance, the formula’s embodiment of systemic racism may be opaque. However, the authors included a small sample of Black subjects, and when the authors attempted to explain why Black “ethnicity” predicted a higher eGFR for the same creatinine value, they did not mention the small sample size as a potential source of error. Instead, they relied on outdated and racist tropes about differences in body composition and muscle mass between races. This fallacious and racist logic crumbled when the formula was validated in Black patients in Ghana3 where the eGFR more closely correlated with the non-African-American formula.

The impact of the systemic racism embedded in this race-based formula is significant. The biggest barrier to transplant is late referral; patients cannot be listed for transplant until their eGFR is less than 20 ml/min. Assigning Black patients a higher eGFR for a given creatinine leads to later referrals for preemptive kidney transplant and can lead to longer times on dialysis compared to white patients. A race-based formula further exacerbates the disparities in kidney transplant and may partially account for the disproportionate number of Black patients who are on dialysis compared to their percentage in the overall population.

This is not the only way systemic racism manifests within the eGFR calculation. According to the United States Census, approximately 10% of Americans do not identify as “White, alone” or “Black or African-American Alone.” These patients, who include Asian and biracial individuals, were not in the original derivation MDRD paper, yet are lumped together under the “non-African American” grouping when their eGFR is calculated. This is particularly problematic because when the formula was tested in East and South Asian countries, the true GFR did not align with either the African-American or non-African-American equation.4 Additionally, the formula exemplifies the “white standard” where white is considered the normal, and “race” requires an adjustment.

For pulmonary function tests, the challenge is a different one: in PFTs, we can measure a true value (a patient’s vital capacity or forced vital capacity), but that value is meaningless in isolation. For interpretation, we need to have a reference standard with which to compare. In this case, systemic racism underpins the creation of the reference standard. A reference standard should be derived from qualities that are fixed and could influence the measurement. In PFTs, consensus is that age, sex, height, and race or ethnicity are fixed markers of lung capacity and lung function that should be used to generate a reference standard.5 PFT reference values have been determined for four ethnic groups: Caucasian, Black, South East Asian, and North East Asian. Importantly, these values exclude South Asians and Africans. The differences seen between groups—especially between white and Black Americans—is regularly attributed to differences in body proportions.5 Like in the eGFR explanation, researchers claim Black and white bodies are substantially different, so much so that it affects organ function.

The most commonly used reference standard for PFTs in the United States derives from the National Health and Nutrition Examination Survey (NHANES) III dataset. This data was used to originate three separate equations: one for Caucasians, one for African-Americans, and one for Mexican-Americans.5 Importantly, race was not self-reported, although ethnicity was. The data showed that for any given height, Caucasian and Mexican-American adults had a higher volume of air exhaled in the first second (FEV1) compared to African-Americans. This finding has been reproduced in other datasets in a variety of countries.

However, these equations fail to acknowledge the history of racism underpinning PFTs. Since the invention of the first spirometer in the 1840s, differences in lung volumes have been used to uphold white supremacy and as a justification for enslavement of Black people or to deny them proper compensation for lung disease stemming from pollution exposure.6

These guidelines, and the beliefs that different races have different body proportions and thus different expected lung function, fail to account for the many other reasons leading to different lung capacity in non-white Americans. Social determinants of health, such as poverty, educational attainment, and tobacco and pollution exposure, are all associated with lower lung volumes.7 By attributing differences exclusively to race, rather than the systemic racism that leads to these disparities, institutions uphold white supremacy and are absolved from making the meaningful changes needed to eliminate social determinants of health.

These calculations and formulae are ubiquitous in medicine and contribute to systemic racism. Undoing the beliefs of the greater medical complex can be challenging, especially when racism hides behind the veneer of data and are promoted by both specialty medical societies and clinicians. Too often, if at all, anti-racism is relegated to the doctoring courses, while the foundational science curriculum continues to conflate race and genetics. We believe it is critical to explicitly point out the racism behind these equations early in medical education, teaching that there is no biological basis of race, and that differences attributed to race are more accurately attributed to racism.

As part of our formal medical school curriculum at the Icahn School of Medicine at Mount Sinai, we introduce the racist underpinnings of the eGFR and PFTs prior to teaching the clinical use of these tests. We place these discussions within the relevant physiology and pathophysiology courses, to demonstrate the relevance of these topics to foundational science and to model the practice of challenging commonly held beliefs and practices. In addition, we apply these skills to the critical appraisal of literature later in our curriculum as our students participate in journal clubs. By asking the question “How might racism be manifesting here?” students challenge assumptions, consider biases and explicitly address racism in the study and practice of medicine. Using this knowledge, and in collaboration with students, we will advocate for our health system to remove the race-based correction factor in all its laboratory and test reporting systems.


  1. Vyas DA, Eisenstein LG, Jones DS. Hidden in plain sight—Reconsidering the use of race correction in clinical algorithms. NEJM. June 17, 2020. DOI: 10.1056/NEJMms2004740.
  2. Levey AS, Bosch JP, Lewis JB, et al. A more accurate method to estimate glomerular filtration rate from serum creatinine: A new prediction equation. Modification of Diet in Renal Disease Study Group. Ann Intern Med. 1999;130(6):461-470.
  3. Eastwood JB, Kerry SM, Plange-Rhule J, et al. Assessment of GFR by four methods in adults in Ashanti, Ghana: The need for an eGFR equation for lean African populations. Nephrology Dialysis Transplantation. 2010;25(7):2178-2187.
  4. Teo BW, Zhang L, Guh J-Y, et al. Glomerular filtration rates in Asians. Adv Chronic Kidney Dis. 2018;25(1):41-48.
  5. Hankinson JL, Odencrantz JR, Fedan KB. Spirometric reference values from a sample of the general US population. Am J Respir Crit Care Med. 1999;159(1):179-187.
  6. Braun L. Breathing Race into the Machine: The Surprising Career of the Spirometer from Plantation to Genetics. U of Minnesota Press; 2014.
  7. Harik-Khan RI, Fleg JL, Muller DC, et al. The effect of anthropometric and socioeconomic factors on the racial difference in lung function. Am J Respir Crit Care Med. 2001;164(9):1647-1654


Tags and Keywords