To put it simply, genotype testing tests the antigens that are native to a person. Phenotype testing tests for all antigens present, including any that have been introduced through transfusions. Genotype testing can protect against antibody reactions from transfusions, but this type of testing is seldom done, even in the Comprehensive Thalassemia Centers. It costs more and makes it harder to match the blood, so few centers are willing to do it, even though a strong case can be made for long term cost effectiveness by reducing the amount of antibody reactions and the medical care involved, but with the medical profession, the long term cost is seldom considered. Also, since the concept of genotype matching of blood is relatively new, many doctors are not even aware of it or the positives involved with using genotype to match blood.
All we can do is to continue to educate and spread awareness. In the meantime, most patients will only have phenotype matching made available. I wish I could suggest more but all I can say is people need to continue to educate their doctors.