This has been assessed by visual examination and fluorescein angiography in 39 subjects with SS disease and homozygous alpha+ thalassaemia and in 39 age/sex matched controls with SS disease but with a normal alpha globin genotype (alpha alpha/alpha alpha).
No differences between S beta(0) thalassaemia and S beta(+) thalassaemia were apparent in HbF levels (which resembled those in SS disease) or in HbA2 levels (which exceeded those in SS disease by 1 year of age).