Department of Virology and Liver Unit, Nagoya City University Graduate School of Medical Sciences Department of Clinical Laboratory, Nagoya City University Hospital Nagoya Daini Red Cross Hospital, Nagoya Clinical Research Center, National Nagasaki Medical Center, Oomura Third Wave Japan Incorporated, Tokyo Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Ichikawa, Japan.
IL28B polymorphism is associated with the response to pegylated interferon-α with ribavirin (PEG-IFN-α/RBV) treatment in chronic hepatitis C patients. As a genotyping assay for IL28B single nucleotide polymorphisms (SNPs) in clinical practice, the Invader Plus assay was developed. The accuracy, intra-assay, inter-assay precision, and the limit of detection of the Invader Plus assay were evaluated. Two SNPs (rs8099917 and rs12979860) associated with IL28B were genotyped by the Invader Plus and TaqMan assay in 512 Japanese patients. In comparison with direct sequencing, the Invader Plus assay showed 99% accuracy in rs8099917 and 100% accuracy in rs12979860. Intra-assay and inter-assay precision were sufficient to use in clinical practice and the detection limit was 1ngDNA/assay. Genotyping by rs8099917 showed that 361 (71%), 144 (28%) and seven (1%) of the patients were major homozygous, heterozygous and minor homozygous types, respectively. Five of the 512 cases (1%) had haplotype differences, but none showed differences between the two genotyping methods. For patients with HCV genotype 1, the prevalence of responders in the major homozygous type was 83.3%, and that of non-responders in the minor heterozygous/homozygous type was 72.5%. A convenient IL28B genotyping method using the Invader Plus assay could be useful to predict the treatment outcome in clinical practice.