Importantly, baseline haemoglobin alone does not determine the need for initial transfusion, and additional transfusion or possible exchange transfusion may be required as total haemoglobin includes a fraction of haemoglobin Bart’s, which is ineffective for oxygen transfer. “Effective” haemoglobin is the target for red cell transfusions and its calculation requires the quantification of Hb Bart’s and HbH fraction [21]. Effective haemoglobin is calculated as follows:

Effective haemoglobin (g/L) = (1 - % Hb Bart’s + % HbH) x total haemoglobin (g/L)