Subjective loss of response immediately prior to routine TNFi therapy can occur in axial spondyloarthritis (axSpA). We investigated clinical outcomes in patients taking the first 3 licenced TNFis and correlated this with recurrence of MRI bone marrow oedema (MRI-BMO).
Proof-of-concept study including axSpA patients established on etanercept (ETA), adalimumab (ADA) or infliximab (IFX) reporting symptom deterioration prior to next dose. MRI/clinical data were collected prior to scheduled dose (v1), 4 days post-dose (v2) and at the time of patient-reported symptom return (v3). MRI spine/sacroiliac joints utilising 3 T were scored using the semi-quantitative Leeds MRI scoring system.
113 clinical assessments and MRIs were performed in 38 participants (ADA = 16, ETA = 12, IFX = 10), mean age 42.1 years ± 24.4(2SD, n = 38), 71.1% male (n = 27/38), 69.7% HLA-B27 positive (n = 23/33). At v1 all patients had high disease activity [ASDAS-CRP = 3 (2.7-3.7)] and 57.9% had MRI-BMO (number of MRI-BMO: ETA = 26, ADA = 59, IFX = 28). Improved clinical responses were seen at v2 [ASDAS-CRP -0.41(-0.81-0.30), p= 0.018; BASDAI -0.58(-2.2-0.52), p= 0.024]. Despite just a 4-day interval between v1 and v2, a numerical reduction in MRI-BMO lesions between v1/v2 was observed (ETA=-6, ADA=-10, IFX=-3). By v3 comparatively fewer new BMO lesions were detected in the ETA and ADA groups compared with IFX (ETA=-1, ADA = +3, IFX = +8), although the numbers were too small to enable testing for statistical significance.
Short-lived fluctuations in MRI-BMO were commoner with longer-acting agents and corresponded with subjective loss of clinical response before next scheduled TNFi dose. Larger studies are need to confirm the possible pathogenic implications of this phenomenon.

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