NPSR1 and rheumatoid arthritis: For this purpose, 19 single nucleotide polymorphisms (SNPs), spanning the entire 220 kb region of the NPSR1 gene, were selected based on reported associations and/or their tagging properties, and genotyped in 1808 RA cases and 888 healthy controls from the Epidemiological Investigation of Rheumatoid Arthritis (EIRA) study.