normal lab values were never designed for everyone
notes on the impacts of race & ethnicity
Reference ranges were never designed to be universal.
But, what does that mean for patients?
When we say ‘normal lab value,’ it means normal for the population we studied — not necessarily normal for you. Race and ethnicity are imperfect proxies, but they can guide more accurate interpretation until we have fully personalized labs. I recently came across a study that showed how ethnicity and race affect lab results and the reference ranges used for interpretation [Lim et al, 2015]. The researchers found significant differences in lab test distributions among White, Black, Hispanic and Asian populations.
A more recent study showed over 50% of common lab tests had significantly different distributions across racial and ethnic groups [Rappoport et al, 2018]. So, how come we don’t consider this factor more often? It is already a known fact that sex and physiology affect lab values. For example, women have naturally lower hemoglobin levels than men due to hormonal differences. And, vitamin D binding levels differ based on melanin concentration. So, the idea that lab values can vary among populations is not far fetched.
Why does this matter? Let’s look at some real-world consequences:
Misclassification: Healthy people could have been flagged as abnormal — causing unnecessary treatment
Missed diagnosis: Patients whose lab values are ‘normal’ by outdated ranges may actually have a disease.
Health disparities: Race-based or universal ranges without context reinforce inequities, especially in kidney disease, anemia, and immune disorders.
We will dive into some specific examples where standard ranges differ among populations of African Americans.
WBC & Neutrophil Counts
African American adults tend to have lower baseline WBC and absolute neutrophil counts compared to European Americans. Yet, we are still considered healthy [Lim et al, 2010]. I am actually one of those people that routinely flag low for WBC count. So, would this affect treatment decisions in situations where a similar patient is being considered for chemotherapy or immunosuppressive therapy… that would be a pretty big impact.
Check out this interesting opinion!
Kidney Function, eGFR
Historically, eGFR equations included a race-based adjustment that increased the estimated kidney function for African American patients. This practice was from an observation of differences in the average creatinine levels. The calculation actually delayed the diagnosis of chronic kidney disease (CKD) for millions of African Americans, which affected early interventions and even transplant listings.
The removal of race coefficients in eGFR equations has helped reclassify patients with early CKD, allowing timely interventions before worsening to renal failure, dialysis, or worse [Tsai et al, 2021]. New research supports race-neutral biomarkers, like cystatin C, could improve equity and accuracy in diagnosing kidney function!
Read this story of how race affected a patient’s diagnosis!
Hemoglobin, MCV & other common lab tests
African Americans generally have slightly lower hemoglobin and hematocrit levels as well as a smaller mean corpuscular volume compared to white Americans. Universal ranges can lead to misdiagnosis of anemia or trigger unnecessary iron supplementation. Again, I am one of these people that flag low on Hgb & HCT testing and I have a high PLT count too. So, I have further testing like iron studies to monitor over time. But, there’s no underlying issue. It is just apart of genetics and adaptations over time.
Why do these biases exist?
Historical lab studies were :
conducted primarily on healthy white males that volunteered for reference studies
small sample sizes were considered from women and minorities in general
limited geographic diversity back in the day
It’s just how science operated at that time.
The assumption was that these volunteers represented “typical” biology.
Later, these values became default reference ranges, published into common practice and education. Even today, many labs still use these ranges, only occasionally updating them with more diverse population data as they collect it over time.
What do you think?
How do you think we can better account for diverse populations without overcomplicating the results?
Feel free to read more related studies below.
Racial/Ethnic-Specific Reference Intervals for Common Laboratory Tests – NHANES analysis, PubMed 26468426
Comparing Ethnicity-Specific Reference Intervals for Clinical Laboratory Tests – OUP JALM, 2019
Race-specific WBC and neutrophil counts – PubMed 20236184
NIH race-neutral eGFR study – nih.gov news release
Removing race multiplier improves CKD detection – PubMed 34849475
Interpreting Normal Values and Reference Ranges for Laboratory Tests – JABFM 38(1):174