The full potential of NGS-based HLA genotyping is currently affected by the lack of sequence information outside the ARD for most named alleles. As of January 2019, full-length HLA-DRB1 alleles are still strongly underrepresented in the IPD-IMGT/HLA database. In particular, only 15% of the CWD alleles are completely covered. While for other HLA genes all alleles are of similar length, the size of HLA-DRB1 alleles varies between 11 and 16 kb, mainly due to the length of intron 1. Large allele size differences present a particular challenge for long-range PCR because amplification of the longer allele is commonly suppressed in the presence of a shorter allele.