Grading of ultrasound Doppler signals in synovitis: does it need an update?

To compare subjective estimation with computerized quantification of synovial perfusion in active RA, develop new quantitative scores, establish quantitative limit values for the respective grades in order to achieve even distribution and compare the new scores with the established semi-quantitative score.

Patients fulfilling the 2010 RA classification criteria in whom US showed power Doppler signals in one or more wrist or MCP joints were included. Right and left wrists and MCP joints 1-5 were examined with dorsal and volar scans. The proportion of the synovium covered by Doppler signals was estimated and quantified electronically in the area with the greatest fraction of colour signals.

Forty-one RA patients [29 females, mean age 62 years (s.d. 14), disease duration 11 years (s.d. 13), 28-joint DAS 5.5 (s.d. 1.3)] were examined. Colour signals were found in 192 of 984 joint regions. Forty-two, 139 and 11 regions were allocated to the semi-quantitative grades 1, 2 and 3, respectively, with electronically calculated colour fractions of 3.9%, 12.6% and 29.7%. The mean estimated colour fractions were lower than the mean measured fractions. An even distribution of the scores was found for estimated colour fractions of >0-10% for grade 1, >10-25% for grade 2 and >25% for grade 3 and for measured colour fractions of >0-6% for grade 1, >6-12% for grade 2 and >12% for grade 3.

This study suggests replacing the semi-quantitative grading system for synovial Doppler US with more evenly distributed quantitative scores that might better reflect treatment response.