August 11, 2022

Genotype-specific blood counts

Vanderbilt researchers report genotype-specific reference ranges to improve interpretation of laboratory blood results in African Americans with a common gene variant that lowers white blood cell counts.

More than 60% of African Americans carry a genetic variant (“Duffy Null”) that lowers white blood cell levels — leading to health care inequities including suboptimal medication dosing and excessive diagnostic follow-up. 

Testing for the Duffy Null genotype and having genotype-specific reference ranges for accurate interpretation of laboratory blood results should improve clinical decision making. 

Minoo Bagheri, MSc, PhD, and colleagues examined the distribution of blood cell counts in individuals of Black race with or without the Duffy Null genotype represented in BioVU, Vanderbilt’s DNA biobank linked to de-identified electronic health records. 

Among 3,739 individuals, 65% had the Duffy Null genotype. Their median white blood cell counts were lower than those who did not have the genotype. Absolute neutrophil counts that were below the clinical threshold for neutropenia were common among those with the Duffy Null genotype. 

The genotype-specific reference ranges reported in Blood Advances may assist clinicians in interpreting laboratory results for individuals with low neutrophil counts, the researchers suggest.

Other VUMC authors of the study include Cecilia Chung, MD, PhD, Alyson Dickson, MA, MTS, Sara Van Driest, MD, PhD, Scott Borinstein, MD, PhD, and Jonathan Mosley, MD, PhD. This research was supported by the National Institutes of Health (grants GM130791, GM132204, HG008341). BioVU and genomic data funding sources are listed here.