Comparison of the BASDAI and the miniBASDAI in assessing disease activity in patients with ankylosing spondylitis

The BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) is the most widely used instrument for the assessment of disease activity in ankylosing spondylitis (AS). Objective. The aims to investigate whether the alternative BASDAI, here termed as the miniBASDAI [(Question (Q) 1 fatigue + Q2 spinal pain) + mean of (Q5 strength morning stiffness + Q6 duration morning stiffness)]/3], measures disease activity more accurately in the subgroup of AS patients without peripheral manifestations. One hundred and ten patients were included in this cross-sectional study according to the modified New York criteria for AS. Clinical and biological parameters were evaluated. The disease activity was evaluated by the BASDAI. We calculated the miniBASDAI by omitting both the peripheral joints and the enthesitis questions: questions 3 and 4. Patients were dichotomized into a "P+" group if peripheral manifestations were present (at least arthritis or enthesitis) and a "P-" group, the subgroup without peripheral involvement (with either arthritis or enthesitis). Correlation of the BASDAI and miniBASDAI with other disease parameters were examined with the Spearman's rank correlation analysis. One hundred and ten patients were recruited. The percentage of patients with pure axial disease manifestation without peripheral involvement "P-group" was 42.7%. We found a similarly good correlation of the miniBASDAI with patient global, physician on disease activity, BASFI, ESR and CRP if compared to the correlation of the original BASDAI with these disease parameters, also in the group without peripheral involvement. Our study suggests that the BASDAI remains valid in assessing disease activity in AS patients with and without peripheral manifestations.