MIP4IBD: An Easy and Rapid Genotyping-by-Sequencing Assay for the Inflammatory Bowel Diseases Risk Loci.

Background: Inflammatory bowel diseases (IBD) are polygenic, with many genetic variants contributing to disease risk. Knowing the genotype of specific variants or calculating a combined genetic risk score benefits translational and functional research. To address this, we developed MIP4IBD, a flexible and cost-effective genotyping-by-sequencing assay using molecular inversion probes (MIPs).

Methods: The assay targets 463 IBD risk variants, and 77 additional relevant variants. Molecular inversion probes capture and library preparation were optimized using 15 IBD DNA samples, comparing genotypes with immunochip. A custom GitHub pipeline was created for data processing, performance testing, and genotype calling. The final design was validated on a larger scale (149 IBD patients, 104 non-IBD controls, and 3 external cell lines), incorporating post hoc quality control criteria.

Results: The assay achieved a 3.5-day turnaround time at €15 per sample with optimal sample throughput, demonstrating a 92.6% success rate in variant capture and genotype concordance rates of 99.3% and 99.6% with Infinium Global Screening Array24 BeadChip and WGS, respectively. A downstream application involved the calculation of a weighted IBD polygenic risk score (PRS), which was significantly higher in IBD patients than controls (mean 0.42 vs -0.49, P = 1.95E-11). Individuals in the highest PRS quartile had a 15.7-fold (95% CI: 6.5-38.3) risk of developing IBD and an earlier age of onset (26 vs 37 years, P = 0.02), compared to the lowest quartile.

Conclusions: MIP4IBD is a validated, scalable genotyping assay targeting IBD risk loci, with an integrated bioinformatics pipeline from sequencing data to genotypes and PRS calculation. Its cost-effectiveness and flexibility for additional variants make it particularly appealing for translational and clinical applications.