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Predictors of Clinical Remission under Anti-tumor Necrosis Factor Treatment in Patients with Ankylosing Spondylitis: Pooled Analysis from Large Randomized Clinical Trials

Objective. Investigate the role and relation of disease duration of different factors for achieving clinical remission with anti-tumor necrosis factor (TNF) treatment in patients with active ankylosing spondylitis (AS). Methods. Data pooled from 4 large (n = 1281) clinical trials were used to compare disease duration subgroups for placebo or sulfasalazine (SSZ) versus etanercept (ETN), which, in turn, were analyzed by age of diagnosis ≤ 40 versus > 40 years, HLA-B27 status, and baseline C-reactive protein (CRP) ≤ upper limit of normal (ULN) versus > ULN using chi-square tests, and ANCOVA. The primary efficacy measure was Assessments of SpondyloArthritis international Society (ASAS) partial remission (PR) after 12 weeks of treatment. Also analyzed were Bath AS Disease Activity Index and Functional Index, AS Disease Activity Scores, and ASAS response rates. Results. Overall, a larger percentage of patients achieved ASAS-PR with ETN versus SSZ or placebo. More patients with ≤ 2-year disease duration treated with ETN experienced partial remission (34%) versus longer disease duration (30%, 27%, and 22% for > 2–5, > 5–10, and > 10 yrs, respectively; all p < 0.05). In the subgroup of patients with both disease duration ≤ 2 years and aged ≤ 40 years at diagnosis, the treatment response was even more pronounced. Similar results were seen in HLA-B27–positive patients in the disease duration ≤ 2-year subgroup. Overall, patients with high CRP at baseline had better treatment responses compared with patients with normal CRP. Conclusion. Treatment response under anti-TNF treatment with ETN at 12 weeks was greatest among patients with disease duration ≤ 2 years and even more pronounced in subgroups of patients ≤ 40 years old or HLA-B27–positive at diagnosis.