EFI region 8 Balkan external proficiency testing for HLA typing: Results of 15 years.

Istanbul Medical Faculty, Department of Medical Biology, as the first EFI-accredited HLA laboratory in Turkey since 1999 has been organizing both national and international quality control tests for HLA typing under the banner of the "Balkan external proficiency testing (BEPT)" encompassing countries from EFI regions 8. The first round of BEPT in 2004 was organized for low-resolution HLA-A,-B typing by molecular methods and 12 centres participated in the exercise. In 2005, low-resolution HLA-DR typing was added, and in 2007, low-resolution HLA-C and DQ typing were added to the exercise and 28 centres participated. In 2015, high-resolution (four digits or higher typing) HLA-A,-B,-C,-DR and -DQ typing added to the exercise and 40 centres participated. In the last 2 years, 2017 and 2018, the number of participating centres increased to 48 and 52, respectively. When the distribution of low-resolution typing methods applied in the exercises were investigated, it was found that 82% of the centres in the first round of BEPT in 2004 used PCR-SSP, whereas in the last round in 2018, 26% of the centres preferred SSP, while the rest used SSO (50%) or SSP and SSO (24%) methods. Methods for high-resolution typing were SBT (41%), NGS (18%), SSO (18%), SSP (6%), SBT + NGS (6%) and SBT + SSP (11%). In 15th trial for BEPT, nomenclature mistake rate was 12%, and erroneous result rate was 6% for HLA samples. The most common mistakes in the exercises were nomenclature mistakes. The EFI Standards Version 7.0 is stated "HLA type can be reported using a hyphen if homozygosity is not proven by family studies." In order to provide standard results among HLA laboratories and since accurate HLA typing leads to significant increase of graft and patient survival, quality control exercises should be performed in all HLA-based tests periodically.