BACKGROUND

TNFalpha blockers have been shown to be highly efficacious in patients with active ankylosing spondylitis (AS).

OBJECTIVE

To identify parameters predicting the clinical response to TNF blockers in AS.

METHODS

Patients with active AS participated in two placebo controlled, randomised trials conducted in Germany with infliximab (n = 69) and etanercept (n = 30), respectively. For inclusion in either trial patients had to have high disease activity (BASDAI >or=4) and a spinal pain score (numerical rating scale 0-10) >or=4 despite treatment with NSAIDs. A major clinical response was defined as a 50% improvement of the initial BASDAI (BASDAI 50) after 12 weeks' treatment with active drug. Logistic regression likelihood ratio tests (univariate and multivariate), Student's t test, and chi(2) tests were performed.

RESULTS

Univariate analysis showed the following to be predictors of a major response (BASDAI 50) to treatment: shorter disease duration (p = 0.003); lower BASFI (p = 0.007); younger age (p = 0.009); raised ESR (p = 0.033); raised CRP (p = 0.035). After adjustment for disease duration, BASFI, ESR, and CRP, but not age, remained significantly associated. After adjustment for disease duration and for BASFI, ESR, CRP, and in addition, a higher BASDAI were significantly associated with response. The best multivariate model built by stepwise regression contained the covariables disease duration, BASFI, BASDAI, and CRP.

CONCLUSION

A shorter disease duration, younger age, and a lower BASFI are predictors of a major clinical response to TNF blockers in active AS. Raised CRP and a higher BASDAI may also be valuable predictors. These data need to be confirmed in further studies.