Table 4. Reduced neutrophil count is more associated to the Duffy null polymorphism than to ancestry.

	χ2 value for association of neutrophil count to a predictor (n = 5,997 individuals passing analysis quality filters)
Carrier status for SNP allele (χ2 from 1-variable regression)	1883.2
Carrier status for European ancestry * (χ2 from 1-variable regression)	1867.9
SNP and ancestry * together (χ2 from 2-variable regression)	1883.6
Association to SNP beyond ancestry (χ2 subtracting lines 3–2, one-sided test)	15.7 (P = 3.8×10−5)
Association to ancestry beyond SNP (χ2 subtracting lines 3–1, one-sided test)	0.4 (P = 0.74)

*: For the association tests, we used ancestry estimates that included the genotype of the SNP. This ensures that any association at the SNP is above and beyond that expected from ancestry alone.