Carrier screening for beta-thalassaemia: a review of international practice

β-thalassaemia is one of the most common single-gene inherited conditions in the world, and thalassaemia carrier screening is the most widely performed genetic screening test, occurring in many different countries. β-thalassaemia carrier screening programmes provide a unique opportunity to compare the delivery of carrier screening programmes carried out in different cultural, religious and social contexts. This review compares the key characteristics of β-thalassaemia carrier screening programmes implemented in countries across the world so that the differences and similarities between the programmes can be assessed. The manner in which thalassaemia carrier screening programmes are structured among different populations varies greatly in several aspects, including whether the programmes are mandatory or voluntary, the education and counselling provided and whether screening is offered pre-pregnancy or antenatally. National and international guidelines make recommendations on the most appropriate ways in which genetic carrier screening programmes should be conducted; however, these recommendations are not followed in many programmes. We discuss the implications for the ethical and acceptable implementation of population carrier screening and identify a paucity of research into the outcomes of thalassaemia screening programmes, despite the fact that thalassaemia screening is so commonly conducted.