Independent risk factors associated with greater acute hematocrit reductions were being G6PD heterozygote in the CQ + PMQ group (mean absolute hematocrit fall of –6.2% [95% CI, –8.4% to –3.9%]; P < .001), age >15 years (–1.0% [95% CI, –2.0% to –.01%]; P = .048), and having a previous history of malaria (–0.66% [95% CI, –1.2% to –0.1%]) (P = .021; Figure 3). The gene discussed is G6PD; the disease is malaria.