SPP1 and rheumatoid arthritis: The analysis revealed the periodontal variables: CAL ≥5 mm, intCAL ≥4 mm, CAL 1-2 mm, CAL 3-4 mm, and PPD >5 mm and the serum inflammatory mediators APRIL/TNFSF13 and osteopontin as important variables (MeanDecreaseGini values >0.5) distinguishing between PD stage II and PD stage III/IV in patients with RA.