This is done by quantifying the HbA2 percentage in a cohort of healthy adults who do not have iron deficiency or the thalassaemia trait.3 The reference interval is a range that should be calculated including individuals with characteristics that are comparable to the reference group so that the reference interval can be correctly applied to the population serviced by the laboratory.7 Given the importance of HbA2 reference ranges, considerable work has been done internationally on normal reference intervals for HbA2. The gene discussed is HBA2; the disease is nutritional disorder.