An increasing number of genetically determined conditions that potentially affect donor health are being identified, and some donors have had specific tests which confirm that they possess variant genes. These include not only the haemoglobinopathies and thalassaemias, but also more recently discovered conditions such as the thrombophilias (e.g. factor V Leiden). Mere possession of such genetic variants does not debar from donation if the donor is otherwise healthy and fulfils all other selection criteria.
This is a special case. Blood from individuals with genetic haemochromatosis (GH) who have no symptoms arising from their GH is intrinsically safe for transfusion. However, before patients with GH who require continued venesection for the maintenance of their health are accepted as blood donors, the consultant with responsibility for donors must ensure that the following criteria are met: