P257 Real-world evidence of TNF inhibition in axial spondyloarthritis: can we generalise the results from clinical trials?
Authors: Jones Gareth T , Dean Linda E , Pathan Ejaz , Macfarlane Gary J 
Published: April 2020

Abstract

Background
The development and utility of management guidelines assumes that clinical trial findings are generalisable. Seldom is data available to test this. We aimed to determine, in the British Society for Rheumatology Biologics Register for Ankylosing Spondylitis (BSRBR-AS), the proportion of patients commencing TNF inhibition (TNFi) that would/would not have been eligible for clinical trials that led to TNFi treatment guidelines, and whether treatment response differed between the trials and this real-world population.

Methods
Biologic-naïve spondyloarthritis patients were recruited from across Great Britain. Data was obtained from clinical records, and participants completed postal questionnaires. Participant characteristics were extracted from the placebo-controlled randomised trials in the NICE Health Technology Assessment: TNF-alpha inhibitors for ankylosing spondylitis and non-radiographic axial spondyloarthritis (TA383). Descriptive statistics were used to examine differences, including treatment response (ASAS-20), between BSRBR-AS participants who would/would not have been eligible for the clinical trials, and the trial participants.

Results
816/2420 (34%) BSRBR-AS participants were commencing TNFi. They were younger (mean age 44 versus 50yrs) with shorter disease duration (15 versus 22yrs), more active disease (BASDAI 6.4 versus 4.0), and poorer function (BASFI 6.2 versus 3.8). Fourteen clinical trials were identified. Compared to trial populations, fewer BSRBR-AS participants were male (67% versus 71%; difference: -4.1% (95%CI: -7.8%, -0.4%)) and fewer were HLA-B27 positive (76% versus 82%; difference: -6.6% (-10.6%, -2.6%)). BSRBR-AS participants were 6yrs older than trial participants, with longer symptom duration. They reported similar disease activity (BASDAI: 6.4 versus 6.2; difference 0.2 (-0.3, 0.7)), although significantly poorer function (BASFI: 6.2 versus 5.1; difference 1.1 (0.5, 1.8)) and spinal mobility (BASMI: 4.2 versus 3.3; difference 1.0 (0.8, 1.1)). Only 333 (41%) of BSRBR-AS participants commencing TNFi would have been eligible for any of the relevant trials. Ten trials reported ASAS20 response criteria, and 864/1401 participants reported a positive treatment response (61.7%). Follow-up data was available for 318 (39%) BSRBR-AS participants, of whom 163 (51.3%) achieved an ASAS20 treatment response (difference: 10.4% (4.4%, 16.5%)). There was no difference in ASAS20 response between those who would/would not have been eligible for clinical trials (50% versus 52%; difference 2.0% (-9.4%, 13.4%)).

Conclusion
In this real-world population, although the likelihood of meeting response criteria was unrelated to factors determining trial eligibility, the proportion of patients responding to TNFi was lower than in the clinical trial literature. Could this be explained by selection bias? Although fewer BSRBR-AS participants provided follow-up data than in the clinical trials, to account for the observed difference participants lost to follow-up would have to be one-third more likely to achieve ASAS20 response than those who provided follow-up data. We believe this is unlikely. These findings have important implications for the generalisability of trial results, and also for the cost-effectiveness of TNFi agents.

Disclosures
G.T. Jones: Grants/research support; GTJ is/was a grant holder for research funded by Pfizer, AbbVie, UCB and Celgene., GTJ is/was involved in research that received financial support from Novartis. L.E. Dean: Grants/research support; LED is/was involved in research that received financial support from Pfizer, AbbVie, UCB and Novartis. E. Pathan: None. G.J. Macfarlane: Grants/research support; GJM is/was a grant holder for research funded by Pfizer, AbbVie, UCB and Celgene., GJM is/was involved in research that received financial support from Novartis.