G6PD and southeast Asian ovalocytosis: With an alpha thalassaemia frequency of 0·68; SAO frequency of 0·07, and G6PD deficient X chromosome frequency of 0.13, all entirely plausible for the Madang region of Papua New Guinea (Flint et al, 1986; Brabin & Brabin, 1990; Patel et al, 2004), the sensitivity of the OTOFT for beta thalassaemia drops to 0.74 in females and 0.69 in males (Fig4 marker A).