3. For non-transfusion dependent subjects: non-transfusion dependency is defined as transfusion free, with the exception of ≤ one episode of transfusion in the period of a minimum of 168 days immediately preceding enrollment (One episode of transfusion is defined as ≤ 4 transfusion units administered, occurring within 168 days immediately preceding enrollment due to concurrent illness [e.g. infection], [Guidelines Clin Management of Thalassaemia, 2008]).