From: Transfusion and Treatment of severe anaemia in African children (TRACT): a study protocol for a randomised controlled trial
R1a Complicated severe anaemia: Hb < 4 g/dl or a Hb < 6 g/dl plus 1 or more signs of severity or complications
R1b Uncomplicated severe anaemia: Hb ≥ 4 and < 6 g/dl without any of the severity features or complications