Radiosynoviorthesis of the knee: a doubleblind trial of 1 versus 5 mCi Gold-198.

Since the minimal effective dosage for radiosynovectomy is not known, we have performed a doubleblind controlled trial of 1 mCi vs. 5 mCi 198Au in 60 knees of 46 patients with persistent rheumatoid synovitis. The therapeutic effect was assessed with a clinical score, 99mTc pertechnetate uptake measurements and plain X-rays. With regard to clinical parameters no statistical differences between the two groups were found, but results indicate a trend towards a better outcome in patients treated with 5 mCi. 99mTc uptake improved significantly in patients treated with the higher dose and not in the low dose group. Weighing ease of treatment and risk of side effects against the small difference in effectiveness, we conclude that the use of less than 5 mCi of 198Au may be justified. During the study the injection technique was changed, enabling a comparison of two methods. Leakage to lymph nodes and liver decreased when the needle was flushed with normal saline after administration of the radiocolloid.