Validation of disease activity and functional status questionnaires in spondyloarthritis

Patients naïve to the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and to the Ankylosing Spondylitis Disease Activity Score (ASDAS) have voiced confusion in our clinics over the use of the term "AS" in these instruments. It is unknown whether these tools may be applied to other related forms of spondyloarthritis (SpA). The Bath Ankylosing Spondylitis Functional Index (BASFI) questionnaire also requires more definitive validation. We 1) validated the BASFI against a standard definition of disability; and 2) validated slightly modified versions of the BASDAI and ASDAS questionnaires that replace references to "AS" with the term "inflammatory arthritis" for use in non-AS SpA.

Adult patients with SpA enrolled in the Veterans Affairs Program to Understand the Longterm outcomes in Spondylo-ARthritis (PULSAR) completed the BASFI, BASDAI, ASDAS and altered versions of the BASDAI (PULSAR-modified Bath Disease Activity Index [PuBaDAI]) and ASDAS (PULSAR-modified Ankylosing Spondylitis Disease Activity Score [PuASDAS]). Spearman correlations and logistic regression were used to analyse the scores.

The correlation between BASDAI and PuBaDAI and between ASDAS and PuASDAS scores was high (Spearman's rho=0.92, p<0.001 and Spearman's rho=0.85, p<0.001, respectively). The test-retest correlation of BASFI was also high (Spearman's rho=0.92, p<0.001). The BASFI (OR 1.67, 95% C.I. 1.12-2.47), ASDAS (OR 1.34, 95% C.I. 1.02-1.76) and PuASDAS (OR 1.62, 95% C.I. 1.07-2.49) predicted federally-determined disability.

Preliminary data suggest that BASDAI and ASDAS scores correlate well with modified forms of these questionnaires and that the ASDAS, PuASDAS and BASFI are associated with disability.