analysis for 2 samples with hladqb1 allele dropout at exon 2 in sequencebased typing objective to explore the reason for hladqb1 allele dropout during routine sequencebased typingsbt in order to improve the accuracy of typingmethods two thousand samples derived from hla highresolution typing laboratory were typed for hladqb1 locus using an alleleseqr hladqb1 sbt kit nonconclusive results and abnormal sequencing samples were retyped using a labtype rsso hd hladqb1 kit and further analyzed with both sequencespecific primers and groupspecific primers and sequenced for haplotype analysisresults among the 2000 samples 2 samples with no conclusive result were identified the heterozygosity was confirmed with both the lab type sso hd hladqb1 kit and pcrsbt in house method subsequent hladqb1 cloning and haplotype sequencing have elucidated that hladqb10202 dropped out at exon 2 for the first sample and hladqb1020101 dropped out at exon 2 for the second sample during pcr amplification no novel nucleotide mutation was foundconclusion our results indicated that preferential amplification at exon 2 of dqb1 may result in allele dropout in exon 2 sequences during hladqb1 sbt test this may provide useful information for hla genotyping