Imaging of inflammatory arthritis with technetium-99m-labeled IgG.

The accumulation of nonspecific polyclonal human immunoglobulin G (IgG) radiolabeled with 99mTc was compared to that of [99mTc]albumin and [99mTc]nanocolloid in rats with collagen induced arthritis. Serial scintigrams were acquired directly, 4 and 24 hr after injection. A clearly discernable image of the site of synovitis was seen with [99mTc]IgG as early as 4 hr postinjection. The relative intensity of the inflammatory lesion was maximal at 24 hr. Discrimination between arthritic and nonarthritic joints as well as correlations between the relative intensity of the arthritic joint and clinical indices of joint inflammation were superior with IgG compared to albumin or nanocolloid. These studies show that localization and severity of inflammatory joint disease can be detected with radiolabeled nonspecific IgG.