Similarities and differences in fluorodeoxyglucose positron emission tomography/computed tomography findings in...

We assessed fluorine-18 ((18)F)-labelled fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) findings in patients with seronegative spondyloarthritis (SpA), polymyalgia rheumatica (PMR), and rheumatoid arthritis (RA).

We studied 53 patients with SpA (n=21), PMR (n=16), or RA (n=16) admitted to our hospital between 2006 and 2011. Disease activity in the ischial tuberosities, greater trochanters, spinous processes, vertebral bodies, and sacroiliac joints (SIJ) were evaluated by determining FDG accumulation using maximum standardized uptake values (SUV(max)) and FDG scores.

SUV(max) for ischial tuberosities was significantly higher in PMR than SpA or RA. SUV(max) for greater trochanters and spinous processes was significantly higher in PMR than RA (P<0.001) and significantly higher in SpA than in PMR or RA for SIJ (P=0.01). No significant difference in vertebral scores was observed among groups (P=0.488). FDG scores yielded similar results. X-ray findings were consistent with PET/CT findings in 3/15 (20%) patients with sacroiliitis, whereas magnetic resonance imaging findings were consistent with PET/CT findings in 4/7 (57.1%) patients.

PET/CT detection of inflammation in the ischial tuberosities, greater trochanters, and spinous processes discriminated between PMR and RA, but not between SpA and PMR. PET/CT findings can distinguish SpA from RA and PMR and are useful for the early diagnosis of sacroiliitis.