OBJECTIVE Musculoskeletal ultrasound quantifies the total synovial inflammatory burden in rheumatoid arthritis (RA) but is time consuming when scanning numerous joints. This study evaluated a novel patient-centered method for constructing a longitudinal ultrasound score in RA patients. METHODS Fifty-four RA patients starting intravenous tocilizumab were evaluated with power Doppler ultrasound (PDUS) of 34 joints and DAS28-ESR was assessed at baseline and weeks 4, 12, 16, and 24. The sentinel joint score (SJS) was derived from the reduced subset of joints with PDUS ≥ 1 at baseline. Total PDUS (tPDUS) score and US7 were also calculated. Changes in tPDUS and SJS were correlated. Effect sizes were calculated for tPDUS, SJS, and US7. The proportion of "flipped" joints without baseline PDUS signal that later developed PDUS signal was estimated. RESULTS At baseline, 1236/1829 joints scanned (67.5%) did not have PDUS signal. The proportion of "flipped" joints at 24 weeks was 5.6% for ≥ 1, 2.9% for ≥ 2, and 1.0% for = 3 PD. tPDUS and SJS scores were highly correlated (r = 0.91 to 0.97). Overall the effect sizes for tPDUS, SJS, and US7 increased over 24 weeks, where SJS was the highest (SJS 1.00 4-week, 1.07 12-week, 1.26 24-week) and tPDUS and US7 were comparable (tPDUS 0.32 4-week, 0.52 12-week, 0.84 24-week; US7 0.23 4-week, 0.52 12-week, 0.74 24-week). CONCLUSIONS In RA patients starting a biologic, scanning only joints with baseline PDUS signal can substantially reduce the number of joints requiring follow-up scanning by 67.5% and improves feasibility. "Flipped" joints are infrequently seen after starting therapy. BACKGROUND ClinicalTrials.gov NCT01717859 Key messages • Only a small percent of joints develop power Doppler signal after baseline scanning. • Changes in the SJS correlate well with changes in clinical activity measured by DAS28-ESR over time. • The SJS effect size is higher than total PDUS and US7 scores, and may improve examination feasibility.