Background/Purpose Bath Ankylosing Spondyltis Metrology Index (BASMI) was developed to quantify the accurate axial status and to assess the clinical changes in spinal movement. The original BASMI was a 3-point scale (range 0-2; BASMI₂), which was refined to an 11-point scale, BASMI₁₀ (range 0-10) to increase the sensitivity to changes of axial status in ankylosing spondylitis (AS). In this study, we compared these BASMI scoring methods in AS patients who were treated with TNF-α blockers.

Methods A retrospective study was conducted in a total of 116 patients who were treated with TNF-α blockers (137 cases; 96 patients with single agent, 19 patients with two, and 1 patient with three). Clinical efficacy was assessed using Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), ASAS20, ASAS40, ASAS5/6, BASDAI50, and acute phase reactants including ESR and CRP at baseline and month 3, and then every six months up to 27 months. Metrology outcome was also evaluated by chest expansion, BASMI₂ and BASMI₁₀ methods at the same time.

Results Three TNF-α blockers including etanercept (60 cases), adalimumab (62 cases), and infliximab (15 cases) showed a similar clinical efficacy. ASAS20 response rate was 87.3%, 91.3%, 91.9%, 90.3%, and 90.9% at months 3, 9, 15, 21, and 27, respectively. ASAS20 responders at month 3 (3MoASAS20) showed a significant improvement of BASMI₂ and BASMI₁₀ scores and chest expansion, compared to those of baseline, while 3MoASAS20 non-responders did not show a significant change until month 27. BASMI₂ scores at baseline and months 3, 9, 15, 21, and 27, were not significant different from those of BASMI₁₀ scores at the same time points. Both BASMI₂ and BASMI₁₀ scores were significantly correlated with components of ASAS20 response criteria including Bath Ankylosing Spondylitis Functional Index (BASFI), BASDAI-spinal inflammation (BASDAI-SI), patient’s global assessment, and pain. The change of BASMI₂ and BASMI₁₀ in 3MoASAS responders was most prominent from baseline to month 3, but still significant from month 3 to month 9. The change of lumbar flexion and lumbar side flexion components of both BASMI₂ and BASMI₁₀ in 3MoASAS20 responders were statistically significant until month 9, while that of other components was only significant until month 3. The improvement of both BASMI₂ and BASMI₁₀ was significantly associated with changes of BASDAI-SI, BASFI, and pain at month 3, 9, 15, 21, and 27.

Conclusion The BASMI₂ method showed similar sensitivity to changes in range of axial motion in patients with AS who were treated with TNF-α blockers. Further studies are required to determine whether BASMI₂ method is as sensitive as BASMI₁₀ method for assessment of axial involvement in AS patient with TNF-α blocker treatment.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-clinimetric-outcomes-of-two-bath-ankylosing-spondyltis-metrology-indices-in-treatment-with-tnf-a-blockers/