Clinical assessment of sacroiliitis and HLA-B27 are poor predictors of sacroiliitis diagnosed by magnetic resonance imaging in psoriatic arthritis.

OBJECTIVE

To determine the frequency and clinical predictors of sacroiliitis diagnosed by magnetic resonance imaging (MRI) in a psoriatic arthritis (PsA) population.

METHODS

The studied comprised 103 patients with PsA. A careful clinical assessment for sacroiliitis was made from history and examination, and HLA-B27 testing was performed. Sixty-eight patients underwent tilted coronal fat-saturated T1-weighted and STIR MRI of the sacroiliac joints.

RESULTS

Clinical features of moderate or severe sacroiliitis were found in 24/68 (35%) patients. MRI features of sacroiliitis were found in 26/68 (38%) patients. Clinical features of sacroiliitis were present in 14/42 (33%) with normal MRI scans and 10/26 (38%) with abnormal scans (normal vs abnormal scans, P = 0.7). The presence of sacroiliitis on MRI was associated with restricted spinal movements (P = 0.004) and the duration of PsA (P = 0.04). There was no correlation between HLA-B27 and sacroiliitis diagnosed by MRI.

CONCLUSION

Sacroiliitis diagnosed by MRI occurs commonly in PsA but is difficult to detect clinically.