G6PD and sleep apnea syndrome: Venous G6PD readings by SDB were significantly higher (mean difference: 0.13 U/g Hb, 95% LoA: −2.86 to 3.11, p < 0.001; S4 Fig, left), while Hb readings from venous blood were also 0.7g/dL higher (LoA: −2.89 to 4.29; S5 Fig) compared to their capillary counterpart (p < 0.001).