Verifying the absolute neutrophil count range for individuals with the Duffy null phenotype

Summary

White blood cell counts, especially neutrophil counts, are commonly measured in blood tests. Doctors use “reference ranges” to decide whether someone’s result is considered normal. But these ranges are not accurate for everyone. 

 Many people of African or Middle Eastern ancestry naturally have lower neutrophil counts due to a common genetic difference called the Duffy null variant. This is a healthy genetic trait that also provides some protection against malaria. However, people with the Duffy null variant are often incorrectly labelled as having “neutropenia” (too few neutrophils), which can lead to unnecessary tests, changes to medication, or exclusion from clinical trials. 

 A small study in Boston developed a more accurate reference range for people with the Duffy null variant. But it’s not yet clear whether those ranges apply to people in other countries or with different backgrounds. 

 Our study brings together data from four countries — the UK, Saudi Arabia, Namibia, and the USA — to create better reference ranges for people with the Duffy null variant. We also plan to include data from a large group of healthy UK blood donors (the STRIDES study) to improve the accuracy and reliability of our findings. 

 By developing Duffy-specific reference ranges for neutrophil and white blood cell counts, this research aims to reduce misdiagnosis and improve care for people whose blood test results are currently misunderstood.