MRI in predicting a major clinical response to anti-tumour necrosis factor treatment in ankylosing spondylitis

Objective: To evaluate the role of MRI in predicting a Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) improvement of at least 50% (BASDAI 50) upon anti-tumour necrosis factor (TNF) therapy of active ankylosing spondylitis (AS). Methods: MRIs from patients with active AS who participated in randomised controlled trials were analysed with respect to presence and extent of active inflammatory lesions as detected in the spine (n = 46), sacroiliac (SI) joints (n = 42) and both sites (n = 26). Univariate and multivariate logistic regression analyses were applied to evaluate MRI and clinical data in predicting a BASDAI 50 response. Results: The Berlin MRI spine score (odds ratio (OR) 1.16, 95% CI 1.02 to 1.33) and disease duration (OR 0.9, 95% CI 0.63 to 0.97) were statistically significant predictors of a BASDAI 50 response using regression analysis while there was only a trend for C-reactive protein (CRP). The likelihood ratio (LR) for achievement of BASDAI 50 was increased in patients with a Berlin MRI spine score >= 11 (LR 6.7), disease duration < 10 years (LR 4.2) and CRP >= 40 mg/litre (LR 3.4). All patients with two or three of these predictors improved clinically (as assessed by BASDAI) by at least 45%. Disease duration > 20 years, normal CRP and no active inflammatory lesion in the spine were highly predictive of not achieving BASDAI 50. A trend was only found for the MRI score of SI joints to be predictive. Conclusions: Widespread inflammation in the spine as detected by MRI contributes to predicting a BASDAI 50 response in active patients with AS treated with anti-TNF agents.