HLA Genotypes in Turkish Hematopoietic Cell Recipients and Likelihood of Finding a Matched Donor Through Family Searches.

Objectives: Allogeneic hematopoietic stem cell transplant is a life-saving treatment, but donor numbers in Turkey do not meet the increasing demand for this procedure. Here, our objectives were (1) to assess the frequency of HLA-matched related donors in the Turkish population and (2) to identify the HLA antigens and haplotypes that are most frequent in Turkey. Materials and Methods: The HLA genotypes of 841 consecutive recipients and 3071 family members were retrospectively reviewed. Results: Matched related donors were identified for 368/841 recipients (44%). Extended family donor searches were performed for 111/181 pediatric recipients (61%), with nonsibling matched related donors found for 23 patients (21%). Matched related donors were found for a significantly higher proportion of pediatric patients (52%) than adult patients (41%) (odds ratio of 2.5; 95% confidence interval, 1.9-4.1; P = .02). The percentage of pediatric versus adult patients with 3 or more siblings was 13% versus 46% (odds ratio of 5.6; 95% confidence interval, 3.6-8.5; P = .001). The most frequent HLA class I antigens at each locus were HLA-A*02 (20.2%), HLA-B*35 (19.5%), and HLA-C*07 (19.8%). The most frequent HLA class II antigens at each locus were HLA-DRB1*11 (21.6%) and HLA-DQB1*03 (40.2%). The most common 3-locus haplotypes were HLA-A 24 B*35 DRB1*11 (F:0.020) and HLA-A 01 B*08 DRB1*03 (F:0.015). When adult and pediatric groups were combined, the most common locus haplotypes were found in 43/345 sibling donors (12%) and in 7/23 nonsibling pediatric donors (30%) (odds ratio of 2.7; 95% confidence interval, 1.2-6.4; p = .02). Conclusions:The results indicate that, in Turkey, it can be beneficial to revise donor search algorithms to include an extended family donor search before an unrelated donor search. This type of search can be effective because of the HLA haplotype diversity in Turkey, the frequency of consanguinity, and the country's limited donor pool.