A NEW APPROACH TO DEFINING FUNCTIONAL ABILITY IN ANKYLOSING-SPONDYLITIS - THE DEVELOPMENT OF THE BATH ANKYLOSING-SPONDYLITIS FUNCTIONAL INDEX

Objective. After pain and stiffness, one of the most important complai nts of patients with ankylosing spondylitis (AS) is disability. The ma in aims of treatment are to control pain but also to improve function. Various methods of assessing function exist but are either not specif ic for the disease or have not been adequately validated. As a result of this deficiency we developed the Bath Ankylosing Spondylitis Functi onal Index (BASFI) as a new approach to defining and monitoring functi onal ability in patients with AS. Methods. This self-assessment instru ment was designed by a team of medical professionals in conjunction wi th patients, and consists of 8 specific questions regarding function i n AS and 2 questions reflecting the patient's ability to cope with eve ryday life. Each question is answered on a 10 cm horizontal visual ana log scale, the mean of which gives the BASFI score (0-10). The questio nnaire was completed 257 times in total: once by 116 outpatients and b y 47 inpatients on 3 occasions over a S-week intensive physiotherapy c ourse. In addition, the instrument was compared with the Dougados func tional index. Results. Patient scores covered 95% of the BASFI range, giving a normal distribution of results. In contrast only 65% of the D ougados functional index scale was used. Furthermore, over the 3 week period of inpatient treatment, the BASFI revealed a significant improv ement in function (20 %, p = 0.004) while there was a less impressive change in the Dougados functional index (6%, p = 0.03). This demonstra tes the superior sensitivity of the BASFI. Consistency was good for bo th indices (p <0.001), as was the relationship between patient percept ion of function and function as assessed by an external observer (p <0 .001). Conclusion. The BASFI satisfies the criteria required of a func tional index: it is quick and easy to complete, is reliable and is sen sitive to change across the whole spectrum of disease.