Background/Purpose: TNF inhibitors (TNFi) are effective treatment in radiographic and non-radiographic axial spondyloarthritis (r-axSpA and nr-axSpA). Nr-axSpA have lower response rate in case of absence of sacroiliitis on magnetic resonance imaging (MRI) or elevated C-reactive protein (CRP) but TNFi efficacy in the absence of clinical, biological or radiological objective signs of axSpA is unknown. The main objective of our study was to compare BASDAI 50 TNFi response rate at 3 months in axSpA depending on the presence or not of objective signs of axSpA.

Methods: Nr-axSpA patients fulfilling ASAS 2009 criteria, without any objective signs defined as the absence at the time of TNFi initiation of radiographic and MRI sacroiliitis, elevated CRP level, dactylitis, anterior uveitis and treated inflammatory bowel disease were included in this retrospective bicentric study between January 2001 and September 2015. They were matched base on a ratio of 1:1, on age, sex and type of TNFi, with axSpA patients having at least one objective sign. Patients had to be treated for at least 3 months with an anti-TNF. The primary outcome of our study was the TNFi efficacy, defined as an achievement of 50% improvement of the initial Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) at 3 months. The secondary outcomes were BASDAI 50 achievement over one year and assessment of predictive factors of TNFi response.

Results: We included 84 nr-axSpA patients without any objective sign and 84 axSpA patients with objective signs. Patients were mostly women (76.2%) with a mean ± standard deviation age of 42 ± 11 years. BASDAI 50 achievement rates were significantly higher in patients with objective signs than in patients without, at 3 months (45.1% versus 13.7%, p<0.0001) and over one year (61.9% versus 21.4% considering all time point for evaluation, p<0.0001). In the total population, positive predictive factors of a BASDAI 50 response achievement at 3 months in univariate analysis were a radiographic sacroiliitis [16/47 (34%) responders versus 22/114 (19.3%) non responders, p=0.038], a sacroiliitis on MRI [19/33 (57.6%) responders versus 18/97 (18.6%) non responders, p < 0.0001], an elevated CRP [16/48 (33.3%) in responders versus 20/114 (17.5%) in non responders, p = 0.025] and a lower mean BASDAI at TNFi initiation [5.4 (1.5) in responders versus 6 (1.5) in non responders, p = 0.017]. Overweight or obesity and sacroiliitis on MRI were respectively a negative and positive predictive factors of TNFi efficacy in multivariate analysis in the all population [OR = 0.32, 95%CI (0.11, 0.96), p = 0.041 and OR = 6.92, 95%CI (2.41, 19.82), p < 0.0001, respectively].

Conclusion: Our study confirms the existence of patients diagnosed with nr-axSpA, according to clinical arm of the ASAS criteria, in whom TNFi have a very low efficacy and should not be used if no objective sign is present at treatment initiation. We also stated high BMI (≥ 25 kg/m²) as a negative predictive factor of TNFi efficacy.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/efficacy-of-tnf-inhibitors-in-axial-spondyloarthritis-according-to-the-presence-of-objective-signs-of-inflammation-a-multicentric-retrospective-study/