GSTM1 and lactic acidosis: Oxygenated Hb absorbs more infrared light; deoxygenated Hb absorbs more red light. The greatest difference between these values could imply a reduced percentage of Hb saturation which may correlate with abnormal CRT (prolonged for flash). Anemia, peripheral vasoconstriction, shock, strong or sharp pain may also increase ΔAb, correlating with abnormal CRT. ΔAb has correlated with degree of lactic acidosis among adult emergency room patients in shock (Oi et al., 2018).