TNFi effectiveness: nonradiographic axial spondyloarthritis vs ankylosing spondylitis
Subjective disease activity is higher in patients with nonradiographic axial spondyloarthritis (nr-axSpA) at start of tumour necrosis factor inhibitor (TNFi) treatment, but outcomes are similar to patients with ankylosing spondylitis (AS) after adjusting for confounders, according to a nationwide cohort study.
In addition, HLA-B27 positivity is associated with better outcomes regardless of axSpA subdiagnosis.
Researchers conducted an observational cohort study based on data from the nationwide DANBIO registry to compare baseline disease activity and treatment effectiveness in biologic-naïve patients with nr-axSpA and AS who started TNFi treatment, as well as to analyse the role of potential confounders (sex/age/start yr/HLA-B27/disease duration/TNFi-type/smoking/baseline disease activity).
Kaplan-Meier plots, Cox and logistic regression analyses were used to assess the effect of diagnosis (nr-axSpA vs AS) and potential confounders on TNFi adherence and response (eg, Bath Ankylosing Spondylitis Activity Index [BASDAI] 50 percent/20 mm).
At TNFi initiation, nr-axSpA patients had higher visual analogue scale scores, compared with AS patients, for pain (median 72 vs 65 mm), global (76 vs 68 mm), fatigue (74 vs 67 mm) and BASDAI (64 vs 59; p<0.01 for all). Patients with nr-axSpA, however, had lower C-reactive protein (7 vs 11 mg) and BAS Metrology Index (20 vs 40; p<0.01 for all).
Median treatment adherence was poorer in nr-axSpA than in AS patients (1.59 years; 95 percent CI, 1.15 to 2.02 vs 3.67 years; 2.86 to 4.49; p<0.0001) in univariate analysis, but not in confounder-adjusted analysis (p>0.05). Both nr-axSpA and AS groups had similar response rates (p>0.05).
HLA-B27 negativity correlated with poorer treatment adherence (HLA-B27 negative/positive, nr-axSpA: hazard ratio [HR], 1.74; 1.29 to 2.36; AS: HR, 2.04; 1.53 to 2.71; p<0.0001 for both) and lower response rates (nr-axSpA: 30 vs 55 percent; AS: 29 vs 54 percent; both p<0.05).
A total of 1,250 TNFi-naïve patients with axSpA were included in the study. Patients with nr-axSpA were more frequently women (50/27 percent) and HLA-B27–negative (25 percent), compared to AS (17 percent; p<0.01).