Objectives: To explore whether changes in a composite ( power Doppler/greyscale ultrasound (PDUS)) synovitis score, developed by the OMERACT-EULAR-Ultrasound Task Force, predict disease activity outcomes in rheumatoid arthritis (RA). Methods: Patients with RA who were methotrexate inadequate responders starting abatacept were evaluated. Individual joint PDUS scores were combined in the Global OMERACT-EULAR Synovitis Score (GLOESS) for metacarpophalangeal joints (MCPs) 2-5, all joints (22 paired) and a reduced (9 paired) joint set. The predictive value of changes in GLOESS at week 1-16 evaluations for clinical status and response (Disease Activity Score (DAS) 28 (C reactive protein, CRP) <2.6; DAS28(CRP) ≤3.2; DAS28(CRP) ≥1.2 improvement) up to week 24, and correlations between DAS28 and GLOESS were assessed. Results: Eighty-nine patients completed the 24-week treatment period. Changes in GLOESS (MCPs 2-5) from weeks 1 to 16 were unable to predict DAS28 outcomes up to week 24. However, significant improvements in GLOESS (MCPs 2-5) were observed at week 12 in patients with DAS28 ≥1.2 improvement at week 24 versus those who did not achieve that clinical response. In patients achieving DAS28 ≥1.2 improvement or DAS28 ≤3.2 at week 24, changes in GLOESS (22 and 9 paired joint sets) were greater in patients who already achieved DAS28 ≥1.2 at week 12 than in those who did not. No significant correlations were found between changes in DAS28 and GLOESS definitions at any time point. Conclusions: PDUS was not correlated with clinical status or response as measured by DAS28-derived criteria, and PDUS changes were not predictive of clinical outcome. The discrepancies require further exploration. Trial registration number: NCT00767325; Results.