Analysis of rs2239657, rs7021880 and rs7021049 stratified by the presence of rheumatoid factor.

aGenotypic P-values were calculated except where indicated.bAll cases in this sample set were RF-positive.cDifferential effects between RF-positive and RF-negative association were determined for sample set 2 using a Breslow-Day test (cases and controls were individually matched).dDifferential effects between RF-positive and RF-negative association were determined for sample set 3 using a Monte Carlo simulation (cases and controls were not individually matched).eIncludes all three sample sets.fIncludes sample sets 2 and 3.