A relatively high percentage of patients with ankylosing spondylitis (AS) receiving anti-tumor necrosis factor (TNF) treatment were found to have low Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) scores and high Ankylosing Spondylitis Disease Activity Score (ASDAS), according to study results published in BMC Musculoskeletal Disorders. Further, patients with low BASDAI and high ASDAS had a greater risk of discontinuing anti-TNF treatment due to its low efficacy, suggesting that BASDAI alone is not a good predictor of anti-TNF treatment efficacy.

While the BASDAI score is a more widely used symptom-based index, the ASDAS is considered more objective as it includes self-reported symptoms as well as laboratory test results and weighted scoring of each parameter. In clinical settings, disease activity indices may not be consistent; however, the accurate measurement of disease activity in patients with AS is important for initiating and maintaining treatment.

The current retrospective cohort study was conducted to determine the prevalence of patients with AS with high disease activity, as measured by the ASDAS-C-reactive protein (CRP), but low BASDAI scores after treatment with anti-TNF agents. Researchers also examined the effect of discordant scores on predicting the continuation of anti-TNF treatment.


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The study included patients with AS who received first-line anti-TNF treatment at a single center between January 2012 and December 2016. Only patients with both BASDAI and ASDAS-CRP scores after 3 months of anti-TNF treatment (6 weeks for infliximab) were included in the current analysis. Patients with low BASDAI scores (<4) were categorized into a high-ASDAS (ASDAS-CRP ≥2.1) or low-ASDAS (ASDAS-CRP <2.1) group. Medical charts were reviewed for demographics, history, laboratory results, ASDAS-CRP, BASDAI scores, and the reason for discontinuation of anti-TNF treatment. Patients were observed until their last visit, discontinuation of anti-TNF treatment, or December 2019.  

A total of 116 patients (mean age, 33.9 years; 94% men) with AS with low BASDAI scores were included in the study. After 3 months of anti-TNF treatment, 45 (38.8%) were categorized into the high-ASDAS group.

Patients in the high-ASDAS vs low-ASDAS group had greater disease activity after 9 months of treatment, as measured by BASDAI scores (2.9±1.1 vs. 2.3±1.4; P =.007), ASDAS-CRP (1.8±0.6 vs 1.5±0.7; P =.079), and proportion of high ASDAS-CRP (27.8% vs 13.8%; P =.094).

Kaplan-Meier survival curves for time to discontinuation of anti-TNF treatment due to lack/loss of efficacy showed that retention rates of anti-TNF agents were significantly lower in the high-ASDAS group (log-rank P =.011), indicating that the BASDAI index alone is not a good predictor of anti-TNF efficacy.

Study limitations included the use of ASDAS-CRP, which is not widely used and may have narrowed the size of the study population and/or resulted in selection bias; the small number of patients who were women; and lack of specificity around the type of anti-TNF agent, dose, or dosing intervals.

“A low BASDAI score after anti-TNF treatment may not be as meaningful as previously thought. About 40% of [patients with] low-BASDAI may have high AS disease activity according to an ASDAS-CRP assessment and be at higher risk [for] discontinuation of anti-TNF treatment due to lack/loss of effectiveness,” the researchers concluded. “We suggest the use of the ASDAS-CRP alone or in addition to the BASDAI when assessing disease activity in patients [with AS] treated with anti-TNF agents.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of the authors’ disclosures.

Reference

Nam B, Koo BS, Lee T-H, et al. Low BASDAI score alone is not a good predictor of anti-tumor necrosis factor treatment efficacy in ankylosing spondylitis: a retrospective cohort study. BMC Musculoskelet Disord. Published online February 4, 2021. doi:10.1186/s12891-020-03941-8