Emerging treatment options in ankylosing spondylitis (AS) are giving new hope to patients with this chronic and potentially disabling disease. Clinical development of new treatments requires that rigorous and well controlled trials be conducted to demonstrate safety and efficacy. A number of classification systems have been developed in recent years as a result of enhanced understanding of the pathogenesis of AS. Although new outcome measures have been developed and a consensus has been reached on the use of assessment instruments in clinical trials, there is still need for improvement and implementation.

The ASsessments in Ankylosing Spondylitis (ASAS) Working Group has addressed some of these dilemmas by establishing a core set of domains for the evaluation of AS and by selecting specific assessment methods for each domain. They have also published improvement criteria for assessing short term improvement with symptom modifying antirheumatic drugs and are presently in the process of developing response criteria for disease controlling antirheumatic treatment. Various experts are also currently examining discrepancies and inadequacies of classification systems for AS. Imaging studies, magnetic resonance imaging, in particular, may provide better classification criteria in the near future.

In addition to consensus on outcome assessment and classification of AS, lessons learnt from clinical trials in rheumatoid arthritis (RA) may serve as a template for AS. Guidance provided by the United States Food and Drug Administration (FDA) for clinical trials in RA may be of particular use. The FDA has defined the claims that sponsors can receive for RA products and the clinical trial data that would be expected to be submitted to support such claims.