Ultrasound colour Doppler measurements in a single joint as measure of disease activity in patients with rheumatoid arthritisassessment of concurrent validity

Objective. Colour Doppler ultrasound (CDU) displays blood flow in the tissues and is able to detect hyperaemia. Because hyperaemia is part of the inflammatory response, the amount of CDU activity in the inflamed synovium may be used to quantify the inflammatory activity in RA. It has never been investigated if the amount of CDU activity in a single joint can be used to quantify disease activity in RA. Methods. A total of 109 patients with RA and affection of the wrist joint underwent a standardized CDU examination assessing three positions in their most affected wrist at start up in biological treatment. On the same day the following measures of disease activity were collected: assessment of the number of tender and swollen joints, CRP, ESR and 28-joint disease activity score (DAS28). The amount of CDU activity was quantified by measuring the percentage of colour in the synoviumthe colour fraction (CF). Correlation between CF and other measures of disease activity was calculated. Results. There was a significant correlation between CF and DAS28 (r 0.29; P 0.001), swollen joint count (r 0.35; P 0.001), CRP (r 0.5; P 0.001) and ESR (r 0.5; P 0.001). No other significant correlations were found. Conclusion. A standardized ultrasound examination of a single affected wrist joint in patients with RA may be used as a measure of disease activity. More studies are needed to identify the number of joints needed to examine by CDU to obtain the best validity of Doppler measurements.