The probability of finding a suitable related donor for bone marrow transplantation in extended families

In bone marrow transplantation, the advantages of family donors over unrelated donors are threefold. (1) Family donors are better matched because they share complete haplotypes. (2) The time between the start of the search and the actual transplantation can be much shorter than for unrelated donors. (3) Related bone marrow transplantation is cheaper. We developed a procedure for calculating the probability of finding a suitable donor among cousins and blood-related aunts and uncles (the extended family). The procedure calculates the following probabilities (P): (1) P that any blood-related uncle or aunt is a suitable donor, (2) P that a suitable donor exists in all blood-related uncles/aunts (from [1]), (3) P that any cousin is a suitable donor (as in [1]), (4) P that a suitable donor exists in all cousins (from [3]), (5) P that a suitable donor exists in the entire extended family (from [2] and [4]). Additionally, we discuss the suitability of this procedure in the daily practice of donor procurement. The procedure is also suitable to search for family donors who have a single antigen mismatch with the patient. We also discuss the differences between our method and the one recently described by Kaufman (Bone Marrow Transplant 15:279, 1995).