(P-IG-37) Redefining the Neutrophil-to-Lymphocyte Ratio by Duffy Blood Group: An International Cohort from Saudi Arabian and American Populations

Background/Case Studies:
Individuals with the Duffy-null (FY_null) phenotype lack the Fya and Fyb antigens of the Duffy (FY) blood group. This is associated with a lower absolute neutrophil count (ANC) without increased susceptibility to infections. Many current ANC reference intervals and clinical decision tools do not account for the expected variation due to the FY_null phenotype. One example of such a tool is the neutrophil-to-lymphocyte ratio (NLR), which is used as a biomarker for assessing systemic inflammation in clinical care and research settings. We aimed to assess differences NLR by FY status in healthy Saudi Arabian and American populations.

Study

Design/Methods:
Two cohorts of healthy individuals were recruited from Makkah, Saudi Arabia, and Boston, United States. For the Saudi cohort, 399 blood donors were enrolled at the blood bank center from Al-Noor Specialist Hospital, Makkah, Saudi Arabia. The American cohort comprised 175 healthy patients identifying as Black or African American at a single primary care center in Boston, United States. FY status was obtained either by serotyping or genotyping and split into binary FY_null and FY-positive cohorts. Complete blood count with differential was recorded. Local ethical approval and participant consent was gained for both cohorts. Comparisons were performed with Mann-Whitney U test.

Results/Findings:
The median NLR for the Saudi FY_null group (n=142) was 0.89 (IQR 0.68–1.26) with a central 95% interval from 0.36 (95% CI: 0.28–0.43) to 2.01 (95% CI:1.93–2.09). Median NLR was 1.25 (IQR 0.97–1.75) for the American FY_null cohort (n=120) with a central 95% interval of range of 0.58 (95% CI: 0.54–0.62) to 2.84 (95% CI: 2.64–3.06). There was a significant difference in NLR between healthy FY_null Saudi and American participants (p< 0.001).

For the Saudi FY-positive group (n=257), median NLR was 1.46 (IQR 1.13–.81) with a central 95% interval of 0.65 (95% CI: 0.60–0.70) to 3.46 (95% CI: 3.41–3.51). Among American FY-positive group (n=55), the median NLR was 2.11 (IQR 1.63–2.87) with a central 95% interval of 0.99 (95% CI: 0.89–1.11) to 4.61 (95% CI: 4.12–5.16). There was a significant difference in NLR between FY-positive Saudi and American participants (p< 0.001).

Conclusions:
NLR in healthy individuals is significantly different between FY_null and FY-positive cohorts from Saudi Arabia and the United States. Unlike FY_null ANC reference intervals, NLR is different among FY_null participants from different countries of origin, even after FY status is accounted for. Normal NLR ratios must be developed locally by FY status before application to research or clinical care. Existing research using NLR should be interpreted with this limitation in mind.