To study the ability of technetium-99m hexamethyl propylene amineoxime (HMPAO) labelled lymphocyte scintigraphy to quantify synovial inflammation, and to analyse the kinetics of lymphocyte retention in the joints of patients with rheumatoid arthritis (RA).
After isolation of the lymphocytes, the cells were radiolabelled in vitro with 250 MBq 99mTc-HMPAO. The scans were performed 30 minutes, three hours and 20 hours after injection.
An increase of the scintigram signal obtained at 20 hours was associated with a high joint swelling and joint pain score (F test = 3.07, p < 0.002), but not with the radiological score. A positive joint scintigram was predictive of active synovitis. Although the scintigram variation over time did not reach statistical significance, the kinetics of the scintigram signal tended to differ according to the disease duration: in early RA, active arthritis could be clearly imaged as early as 30 minutes, increased at three hours and the signal intensity persisted at 20 hours. In contrast, in long standing disease, the affected joints were imaged at 30 minutes, persisted unchanged at three hours, and the scintigram score decreased significantly at 20 hours.
The study shows that 99mTc-HMPAO joint scintigraphy may be used to detect and to localise active rheumatoid arthritis.