Background Power Doppler ultrasound (US) of synovial tissue has become an important tool for estimating inflammatory activity in rheumatoid arthritis (RA). Most studies are currently using the following score: Grade 0; no flow in the synovium; grade 1, ≤3 single vessel signals; grade 2, confluent vessel signals in <50% of the synovium; grade 3, vessel signals in >50% of the synovium. However, the majority of inflamed joints are classified as grade 2. New US technology allows measuring the percentage of a synovial area covered by Doppler signals.
Objectives To compare estimation and computerized measurement of synovial perfusion in active RA, to develop a new quantitative score, to establish quantitative limit values for the respective grades in order to achieve equal distribution, and to compare the new score with the old semi-quantitative score.
Methods Patients fulfilling the 2010 RA classification criteria with joint swelling and US showing power Doppler signals of ≥1 wrist or MCP joint were included. Both wrists and all MCP 1-5 joints were examined in 2 centres, with dorsal and volar longitudinal views that included scans up to 45° medially and laterally from a dorsal or palmar scan. The examination was done with a GE Logiq E9 US machine equipped with an 8-18 MHz hockey stick probe. US machine settings were standardized as follows: PRF, 0.5 KHz; grey scale frequency, 18 MHz; power Doppler frequency, 10 MHz; wall filter 32; colour Doppler priority 100%. The colour gain was adjusted just below the appearance of artefacts. The power Doppler box included all visible joint areas. Measurement was done in the area with the greatest fraction of colour Doppler signals. Findings were graded according to the old classification. The proportion of the synovial area covered by colour Doppler signals was estimated by the sonographer and measured with the new software.
Results Fourty-one RA patients, 29 females, age 62 (SD 14), disease duration 11 years (SD 13 years), DAS 28 5.5 (SD 1.3), CRP 25 mg/dl (SD 40), were examined. No colour signals were found in 790 joint regions. Table 1 shows the results for the old classification:
The mean estimated colour fraction was lower than the mean measured colour fraction. A score related to the colour fraction could provide a more equal distribution with the equipment used in this study (Table 2).
Conclusions This study suggests replacing the old semi-quantitative grading system for synovial power Doppler US by a quantitative score with the aim of providing more equal distribution of inflamed joints and for increasing the sensitivity to change particularly for joints that have been classified as grade 2 by the old grading system.
Acknowledgements The ultrasound equipment was provided by General Electric
Disclosure of Interest W. Schmidt Grant/research support: GE, Esaote, Siemens, V. Schönau: None declared, B. Reiche: None declared, S. Ohrndorf: None declared, P. Oberdorfer: None declared, M. Backhaus Grant/research support: GE, Esaote