GSTM1 and alpha thalassemia spectrum: Model covariates are SCT; Sickle cell trait (Hb AS), Hb AA; Sickle cell normal: Alpha thalassemia variants (αα/αα, -α3.7/αα), G6PD African variant: B; WT, A-; (202 C > T/376T > A), A;(376T > A).