ADA and rheumatoid arthritis: Similar to the observations for CDAI, 75% improvement in SDAI had the most discriminatory ability for both the lowest P value and the greatest treatment difference between ADA+MTX and PBO+MTX treatment for patients in early RA trials at week 26 (Fig. 3a, b and Additional file 1: Table S1); at week 12, the highest discriminatory ability was between SDAI 70–80% for both trials.