Higher anti-tumour necrosis factor-α levels correlate with improved radiological outcomes in Crohn's perianal fistulas.

Abstract

Higher anti-tumour necrosis factor-α drug levels are associated with improved clinical healing of Crohn's perianal fistulas. It is unclear whether this leads to improved healing on radiological assessment. We aimed to evaluate the association between anti-tumour necrosis factor-α drug levels and radiological outcomes in perianal fistulising Crohn's disease. A cross-sectional retrospective multicentre study was undertaken. Patients with perianal fistulising Crohn's disease on maintenance infliximab or adalimumab, with drug levels within 6-months of perianal magnetic resonance imaging were included. Patients receiving dose changes or fistula surgery between drug level and imaging were excluded. Radiological disease activity was scored using the Van Assche Index, with an inflammatory sub-score calculated using indices: T2-weighted imaging hyperintensity, collections >3mm diameter, rectal wall involvement. Primary endpoint was radiological healing (inflammatory sub-score≤6). Secondary endpoint was radiological remission (inflammatory sub-score=0). Of 193 patients (infliximab, n=117; adalimumab, n=76), patients with radiological healing had higher median drug levels compared to those with active disease (infliximab 6.0 versus 3.9μg/mL; adalimumab 9.1 versus 6.2μg/mL; both, P<0.05). Patients with radiological remission also had higher median drug levels compared to those with active disease (infliximab 7.4 versus 3.9μg/mL, P<0.05; adalimumab 9.8 versus 6.2μg/mL, P=0.07). There was a significant incremental reduction in median inflammatory sub-scores with higher anti-tumour necrosis factor-α drug level tertiles. Higher anti-tumour necrosis factor-α drug levels were associated with improved radiological outcomes on magnetic resonance imaging in perianal fistulising Crohn's disease, with an incremental improvement at higher drug level tertiles for both infliximab and adalimumab.