Joint scintigraphy and erosions.

Correspondence Joint scintigraphy and erosions SIR, Isotope studies have been widely used in rheumatol-ogy for about 20 years. The study by Desaulniers and coworkers indicated that skeletal scintigraphy was a more sensitive method for the detection of inflammatory joint disease than radiography.' It appeared to be more sensitive than clinical evaluation in the diagnosis of joint inflammation of wrists, hands, ankles, and feet. We read with interest the study of Pitt, Berry, Clarke, and coworkers, in which x rays and joint scans with "mTc methylene diphosphonate (v9mTc MDP) were compared.2 They found no association between the uptake of isotope in the hands and the development of new erosions. They studied 10 patients with RA whose hands were x rayed at 0 and 12 months, whereas "mTc MDP scanning was performed only at the beginning of the study. Five patients had 30 eroded joints, 57% of which were scintigraphically active. The high proportion of scinti-graphically negative erosions at the start of the study is not surprising since patients with early RA were not included. The duration of disease was 11 years on average (range 2-47) and obviously many joints with erosions would have been clinically inactive for years. Data on clinical activity of the joints were not presented. Demonstration of an old erosion by scintigraphy is not important as erosions can be seen in x ray pictures. The interesting question is how valuable joint scanning is in predicting the joints to be eroded. The x rays done after 12 months' follow up showed 28 new erosions, of which 46% were in scintigraphically active joints.2 Development of a new erosion in a joint which was negative on scanning 12 months earlier does not argue against the predictive value of scanning because arthritis may exacerbate during the period of observation. The inflammation in a joint may decrease, remain unchanged, increase, or start in a previously inactive joint during the follow up period of one year. We have followed up 16 newly diagnosed patients with RA (average duration 10 months) for 18 months with careful serial clinical assessment (Ritchie index and joint effusion) and with "mTc MDP scintigraphy of peripheral joints (n=477) at 0, 6, and 12 months. "mTc MDP with an activity of 370 MBq/m2 was injected, and pictures were taken after three hours. The collection 128x 128 word matrix was used. Visual measurement (normal, slight, or clear contrasts) of metacarpophalangeal, proximal inter-phalangeal, …