In addition, the level of phosphorylated C-terminal end of OPN fragment was higher in both the seropositive (mean ROD 0.201±0.024, median 0.204) and the seronegative (mean ROD 0.217±0.053, median 0.206) RA patients than in the OA patients (mean ROD 0.165±0.006, median 0.165), p<0.05, and there was no significant difference between seropositive and seronegative groups, as shown in Fig 1C. This evidence concerns the gene SPP1 and rheumatoid arthritis.