P0260 Scoring indices grading radiologic disease activity severity on magnetic resonance imaging strongly reflect clinical healing of Crohn’s perianal fistulas
Authors: De Gregorio M , Winata L S , Behrenbruch C C , Hartley I , Connor S J , D'Souza B , Johnston M J , Kamm M A , Keck J O , Rimola J , Sutherland T , Woods R J , Wright E K , Connell W R , Thompson A J , Ding N S 
Published: January 2025

Abstract

Background
Magnetic resonance imaging (MRI) is the gold-standard for evaluating Crohn’s perianal fistulas. Multiple scoring indices to grade radiologic disease activity severity have been established, with limited comparative data and a lack of consensus regarding which index correlates most accurately with clinical findings. In a prospective MRI series, we explored the relationship between established radiologic indices and clinical healing.

Methods
Serial MRI scans from 60 adults with Crohn’s perianal fistulas enrolled in a prospective study were acquired. The prospective study evaluated the efficacy of a protocolised treatment strategy optimising care delivery at a single tertiary centre. Patients had ≥12 months follow-up with serial MRI performed annually. Each MRI scan had a paired physical examination, with clinical healing defined as the absence of externally draining perianal fistulas and no seton. MRI scans were reviewed by a specialist radiologist blinded to clinical findings. Radiologic disease activity severity was graded using the Van Assche Index (VAI), Magnetic Resonance Index for Assessing Fistulas in Patients with Crohn’s Disease (MAGNIFI-CD) and Fibrosis Score (FS). The primary endpoint was the relationship between radiologic indices and clinical healing. Secondary endpoints included the optimal index scores for clinical healing and the relationship between individual scoring criteria and clinical healing.

Results
A total of 135 MRI scans were acquired. All patients had baseline imaging, with 88% and 37% having serial imaging at 1 and 2 years, respectively. The median interval between baseline and final MRI was 16 months. Clinical healing significantly correlated with less severe radiologic disease activity, reflected by lower VAI (OR 0.70, P&lt;0.001), lower MAGNIFI-CD (OR 0.76, P&lt;0.001) and higher FS (OR 3.14, P&lt;0.001). On ROC curve analysis, all radiologic indices exhibited a similarly high degree of correlation with clinical healing; AUROC of 0.91, 0.84 and 0.92, respectively (Figure 1). The optimal index scores for clinical healing were VAI ≤6 (sensitivity 83%, specificity 94%, AUROC 0.88), MAGNIFI-CD ≤8 (sensitivity 78%, specificity 73%, AUROC 0.75) and FS ≥5 (sensitivity 83%, specificity 94%, AUROC 0.88). On multivariable logistic regression analysis, increasing degree of fibrosis on FS (OR 2.68, P&lt;0.001) and increasing fistula tract extension on VAI (OR 0.09, P&lt;0.001) were independent positive and negative indicators of clinical healing, respectively.

Conclusion
Radiologic disease activity severity using established scoring indices have equally strong correlations with clinical healing of Crohn’s perianal fistulas. Further studies are needed to explore the predictive utility of individual radiologic parameters.