High BMI is associated with lower TNF-α inhibitor serum trough levels and higher disease activity in patients with axial spondyloarthritis.

"Declarations Ethics approval and consent to participateAll data were obtained within the GLAS cohort, which was approved by the local ethics committees of the MCL and UMCG. All patients provided written informed consent according to the Declaration of Helsinki. Consent for publicationNot applicable. Competing interestsL. de Wolff: no financial disclosures.S. Arends: research grant from Pfizer.E. Brouwer: no financial disclosures.H. Bootsma: no financial disclosures.A. Spoorenberg: grant/research support from Abbvie, Pfizer, UCB, Novartis, consultant for Abbvie, Pfizer, MSD, UCB and Novartis. Competing interests L. de Wolff: no financial disclosures. S. Arends: research grant from Pfizer. E. Brouwer: no financial disclosures. H. Bootsma: no financial disclosures. A. Spoorenberg: grant/research support from Abbvie, Pfizer, UCB, Novartis, consultant for Abbvie, Pfizer, MSD, UCB and Novartis."

"Funding The GLAS cohort was supported by an unrestricted grant from Pfizer pharmaceuticals. Pfizer had no role in the design, conduct, interpretation, or publication of this study."