RELEVANCE OF 10 CAUCASIAN HLA HAPLOTYPES IN SEARCHES FOR UNRELATED BONE-MARROW DONORS FOR 100 PATIENTS FROM A SINGLE-CENTER

Unrelated donor searches for 100 Caucasian patients were referred to F rance Greffe de Moelle Registry (FGM) from September 1987 (24600 donor s) to December 1993 (71500 donors, 61% DR typed), After DR typing of H LA-A,B matched donors, unsuccessful searches were extended to other Eu ropean Registries for 36 patients, Twenty two patients had a donor (FG M: 19, other Registries: 3) selected on: (1) HLA-A,B and DRB,DQB1 spli t identity; and (2) unidirectional relative response <5% in MLR perfor med twice, Estimated probability of finding a compatible donor at 9 mo nths in FGM was 12% (s.e. +/- 4%) and 25% at 2 years (s.e. +/- 6%), Th is probability was stringently dependent on a phenoidentity to one ver y common HLA-A,B,DR or B,DR haplotype (25% at 9 months when present, r epresenting 19 of 19 patients with a compatible donor), Without this p henoidentity, the probability was zero per cent (P = 0.0001) in FGM se arches and <4% (n = 1) in extended searches, The MLR test was shown to be insensitive for screening for DPB1 mismatches, Clinical status inf luenced the probability of finding a compatible donor at one year rang ing from 9% +/- 9% for ALL to 23% +/- 8% for CML (NS), Disregarding DP B1 mismatches is the most efficient way of increasing search efficienc y.