Developing a reference system for the IFCC standardization of HbA₂

The importance of hemoglobin A₂ (HbA₂) as an indicator of the presence of β-thalassemia was established many years ago. However, clinical application of recommended HbA₂ cut off values is often hampered due to poor equivalence of HbA₂ results among methods and laboratories. Thus, the IFCC standardization program for HbA₂ was initiated in 2004 with the goal of achieving a complete reference system for this measurand. HbA₂ standardization efforts are still in progress, including the development of a higher-order HbA₂ reference measurement procedure and the preparation of a certified reference material in collaboration with the IRMM. Here, we review the past, present and future of HbA₂ standardization and describe the current status of HbA₂ testing.