Bone scintigraphy in axial seronegative spondyloarthritis patients: role in detection of subclinical peripheral arthritis and disease activity.

Aim: To detect subclinical peripheral arthritis and disease activity in axial seronegative spondyloarthritis (SpA) patients using bone scintigraphy.
Methods: Seronegative SpA patients with an established diagnosis and no clinically evident arthritis at the time of the study were included. After excluding symptomatic cases, 20 patients were recruited; 18 with ankylosing spondylitis (AS) and another two with psoriatic arthritis (PsA). Conventional bone scintigraphy was performed to detect the distribution of increased uptake, blood vascular pool (vascularity) and activity.
Results: The peripheral joints in all the patients were asymptomatic with no signs of arthritis on clinical examination. Disease activity was higher in those with hypervascularity and activity (75%) detected by scintigraphy. Scintigraphic activity of the sacroiliac joints was found in 10 patients (50%) with a mean sacroiliac joint index of 2.4 ± 0.6. Subclinical involvement of the hips, knees, shoulders, ankles, small joints of the hands, ankles and sternoclavicular joints, as well as the small joints of the feet were detected with descending frequencies (25%, 25%, 20%, 20%, 15%, 10% and 10%, respectively). Dorsal spine increased uptake was found in 35% and hypervascularity of the skull in two cases. Avascular necrosis of the hip was present in one case with hypovascularity.
Conclusion: The spectrum of joint involvement in seronegative SpAs should not be limited to sacroiliitis. Bone scintigraphy provides a cost-effective method for detecting the extent of involvement in this group of autoimmune systemic diseases (axial SpA) without clinical evidence of peripheral arthritis.
(© 2014 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty Ltd.)