A NEW APPROACH TO DEFINING DISEASE STATUS IN ANKYLOSING-SPONDYLITIS -THE BATH ANKYLOSING-SPONDYLITIS DISEASE-ACTIVITY INDEX

Objective. Disease status, in terms of disease activity, disease progr ession and prognosis is difficult to define in ankylosing spondylitis (AS). No gold standard exists. Therefore, the Bath Ankylosing Spondyli tis Disease Activity Index (BASDAI), a self-administered instrument, h as been developed as a new approach to defining disease activity in pa tients with AS. Methods. The index, designed by a multidisciplinary te am with input from patients, consists of six 10 cm horizontal visual a nalog scales to measure severity of fatigue, spinal and peripheral joi nt pain, localized tenderness and morning stiffness (both qualitative and quantitative). The final BASDAI score has a range of 0 to 10. The index was distributed to a cross section of patients, including inpati ents receiving 3 weeks of intensive physiotherapy treatment and hospit al outpatients. BASDAI was completed by a total of 154 patients. Valid ation of the new instrument was achieved through analysis of user frie ndliness, reliability (consistency), score distribution and sensitivit y to change. Comparisons were made with a previous Bath disease activi ty index (DAI) and the Newcastle Enthesis Index. Results. The BASDAI w as found by patients to be quick and simple to complete (mean: 67 s). Test-retest reliability was good (r = 0.93; p <0.001), as was the dist ribution of scores across the scale (score range: 0.5-10; mean: 4.31). BASDAI was sensitive to change, reflecting a 16% (mean) improvement i n inpatient scores after 3 weeks of treatment. It is superior to the D AI in terms of construct and content validity and to the Enthesis Inde x in all aspects. Conclusion. In summary, BASDAI is user friendly, rel iability, sensitive to change and reflects the entire spectrum of dise ase. It is a comprehensive self-administered instrument for assessing disease activity in AS.