[Magnetic resonance imaging for active ankylosing spondylitis]

To diagnoze active ankylosing spondylitis (AAS) by magnetic resonance imaging (MRI).

MRI of the sacroiliac joint (SIJ) was performed on 48 patients who were clinically diagnosed as probable AS without radiologic evidence of sacroiliitis. Among them 21 were diagnozed as active sacroiliitis with MRI, whose examination was terminated; 27 whose MRI of SIJ did not diagnoze as active sacroiliitis were performed MRI in the thoracic spine. The diagnostic criteria of MRI for AAS of SIJ and/or the thoracic spine were fomulated by consulting documents. The definite diagnosis of AAS was finally made after follow-up for half a year. The sensitivity and specificity of the MRI of SIJ and/or MRI of thoracic spine were assessed.

In the 48 patients without radiologic evidence of sacroiliitis, 38 were finally diagnosed as AAS, with established consensus criteria as reference standard. The sensitivity and specificity of the MRI of SIJ were 52.6% and 90.0%, and for the MRI of SIJ and/or the MRI of the thoracic spine 76.3% and 90.0%, respectively.

Clinically probable AS without MRI evidence of sacroiliitis, MRI of the thoracic spine can increase the sensitivity of AAS diagnosis.