DNA was extracted from 200 μl of saliva collected with the Oragene self-collection kit (DNA Genotek®) using the silica-based Kleargene DNA extraction method. Genotyping analyses of the single nucleotide polymorphism (SNP) rs1360780 were performed using the Kbioscience Allele-Specific Polymorphism assay based on competitive allele-specific PCR and bi-allelic scoring. No-template control samples were included to enable the detection of contamination or non-specific amplification.
