Worse scores but similar patterns of disease activity: interpreting outcomes in women with axial spondyloarthropathy

Construct validity of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Ankylosing Spondylitis Disease Activity Score (ASDAS) treatment target cut-offs in a BASDAI treat-to-target axial spondyloarthritis cohort: a cross-sectional study

OBJECTIVE

In axial spondyloarthritis (axSpA), the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Ankylosing Spondylitis Disease Activity Score (ASDAS) are recommended for use in treat-to-target (T2T) strategies. However, BASDAI disease states may be a less suitable T2T instrument than ASDAS, since BASDAI contains non-disease activity related items. The objective of our study was to investigate the construct validity of BASDAI and ASDAS disease states.

METHOD

We performed a single-centre cross-sectional study on BASDAI and ASDAS construct validity in long-term BASDAI T2T-treated axSpA patients. Our hypothesis was that BASDAI is less representative of disease activity than ASDAS owing to the focus on pain and fatigue, and missing an objective item, e.g. C-reactive protein (CRP). This was operationalized using several subhypotheses.

RESULTS

The study included 242 axSpA patients. BASDAI and ASDAS disease states showed a similar relation to Patient Acceptable Symptom State and T2T protocol adherence. The proportions of patients with high BASDAI and ASDAS disease activity fulfilling Central Sensitization Inventory and fibromyalgia syndrome criteria were similar. The correlation with fatigue was moderate for both BASDAI (Spearman's rho 0.64) and ASDAS (Spearman's rho 0.54) disease states. A high ASDAS was strongly correlated with increased CRP (relative risk 6.02, 95% CI 3.0-12.09), while this correlation was not seen for BASDAI (relative risk 1.13, 95% CI 0.74-1.74).

CONCLUSION

Our study showed moderate and comparable construct validity for BASDAI- and ASDAS-based disease activity states, with the expected exception of association with CRP. Therefore, no strong preference can be given for either measure, although the ASDAS seems marginally more valid.

Impact of sex and gender on axSpA diagnosis and outcomes

Axial spondyloarthritis (axSpA) was historically considered a disease of men, largely due to the recognition of a more severe, progressive phenotype, ankylosing spondylitis (AS; or radiographic axSpA, r-axSpA) aiding the clinical diagnosis [1,2]. Data demonstrating the near equal prevalence of axSpA in women only started to emerge in the last decades, highlighting intrinsic differences in disease phenotype, and clinical and imaging characteristics between sexes, which partly explain the issue of underdiagnosis in women. Similar to the evolving understanding of spondyloarthritis and the diseases that term describes, the concepts of gender and sex also warrant further clarification to accurately assess their potential role in disease pathophysiology and phenotypic expression. This narrative review delves into the most recent evidence from the literature on the true prevalence of sex differences in axSpA, and the impact of sex and gender on diagnosis, disease characteristics and treatment response in this, still underserved, chronic disease.

Does gender influence outcome measures similarly in patients with spondyloarthritis? Results from the ASAS-perSpA study

OBJECTIVES

To investigate the influence of gender on disease outcomes in patients with spondyloarthritis (SpA), including across SpA subtypes.

METHODS

Data from 4185 patients of 23 countries with a diagnosis of axial SpA (axSpA), peripheral SpA (pSpA) or psoriatic arthritis (PsA) from the Assessment of SpondyloArthritis International Society (ASAS)-perSpA study were analysed. Associations between gender and disease activity (Ankylosing Spondylitis Disease Activity Score (ASDAS), Bath Ankylosing Spondylitis Disease Activity Score (BASDAI), C-reactive protein (CRP)), function (Bath Ankylosing Spondylitis Functional Index (BASFI)) and overall health (ASAS Health Index (ASAS HI), European Quality of Life Five Dimension (EQ-5D)) outcomes were investigated. Multilevel multivariable linear mixed models adjusted for relevant confounders (and stratified by disease subtype in case of a relevant interaction) were used.

RESULTS

In total, 65%, 10% and 25% of patients had axSpA, pSpA and PsA, respectively. axSpA was more frequent in males (68%), whereas pSpA and PsA were more frequent in females (53% and 52%, respectively). A significant interaction between gender and disease subtype was found for ASDAS, BASDAI and BASFI. While being female independently contributed to higher BASDAI across the three disease subtypes (with varying magnitude), female gender was only associated with higher ASDAS in pSpA (β (95% CI): 0.36 (0.15 to 0.58)) and PsA (0.25 (0.12 to 0.38)) but not in axSpA (0.016 (-0.07 to 0.11)). No associations were observed between gender and CRP levels. Female gender was associated with higher ASAS HI and EQ-5D, without differences across disease subtype.

CONCLUSION

Female gender is associated with less favourable outcome measures across the SpA spectrum. However, while female gender influences BASDAI across the three subtypes, ASDAS is associated with gender only in pSpA and PsA but not in axSpA. Therefore, ASDAS is an appropriate instrument both for females and males with axSpA.