Genetic determinants of G6PD deficiency status. a, G6PD activity distribution stratified by genotype at c.202G>A. b, G6PD activity in 202AG heterozygotes stratified by genotype at c.376A>G (NB: the 202A derived allele always exists on a 376G derived allele background), with contingency table (inset) for qualitative test of association at c.376A>G in 202AG heterozygotes. Also shown in both plots is the reference line (blue) dividing normal vs. deficient for qualitative tests of G6PD deficiency. In box-and-whisker plots, center of box represents median, edges of box represent upper and lower quartile bounds, and whiskers represent either minimum and maximum values or 1.5 times the interquartile range, whichever is less extreme.