Joint scintigraphy for quantification of synovitis with 99mTc-labelled human immunoglobulin G compared to late phase scintigraphy with 99mTc-labelled diphosphonate.

The ability of scintigraphy with technetium 99m-labelled polyclonal human immunoglobulin G (99mTc-IgG) to detect and quantify arthritis activity was studied in 24 patients with RA and in 10 patients with OA. The results of 99mTc-IgG scintigraphy were compared with those of scintigraphy with 99mTc-labelled hydroxymethylene-diphosphonate (HDP). The mean joint scores of 99mTc-IgG scintigraphy in RA patients with active disease were significantly higher (P < 0.001) than the mean scores in patients with inactive disease. The mean joint scores were also higher in patients with erosions compared to those in patients without erosions (P < 0.05). For 99mTc-HDP scintigraphy no significant differences were found between the mean joint scores of these patient groups. Comparison of scintigraphic results between patients with RA and OA revealed that the mean joint score of 99mTc-IgG scintigraphy was significantly (P < 0.001) higher in the patients with RA than in patients with OA, whereas for 99mTc-HDP scintigraphy this difference was not significant. These results show that 99mTc-IgG scintigraphy, when compared to 99mTc-HDP scintigraphy, is a more specific method of detecting synovitis and, also, shows differentiation between different degrees of arthritis activity in RA.