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P188 Validation of the modified Van Assche index for assessing response to anti-TNF therapy with MRI in perianal fistulising Crohn’s disease

K. van Rijn*1, C. Lansdorp2, J. Tielbeek1, C. Nio1, C. Buskens3, G. D'Haens4, M. Löwenberg4, J. Stoker1

1Amsterdam UMC – Location AMC, Radiology and Nuclear Medicine, Amsterdam, The Netherlands, 2Amsterdam UMC – Location AMC, Anaesthesiology, Amsterdam, The Netherlands, 3Amsterdam UMC – Location AMC, Surgery, Amsterdam, The Netherlands, 4Amsterdam UMC – Location AMC, Gastroenterology, Amsterdam, The Netherlands

Background

Magnetic resonance imaging (MRI) is used to assess perianal fistulising Crohn’s disease (CD). Evaluation of treatment responses is crucial to guide clinical decisions. The original Van Assche index was modified to improve sensitivity to change, leading to the modified Van Assche index.1 We aimed to validate the modified Van Assche index in patients with perianal CD receiving anti-TNF therapy.

Methods

An electronic search of medical records (2008–2018, Amsterdam UMC location AMC) was performed. Patients with a confirmed diagnosis of fistulising perianal CD who started or underwent intensification of anti-TNF treatment with a baseline and follow-up pelvic MRI were identified. Patients were divided in clinical responders and non-responders based on the medical notes at the time of the follow-up MRI. Items of the original and modified Van Assche index were scored in random order by two blinded, independent abdominal radiologists (JAWT and CYN), discrepant reads were reassessed by a third blinded abdominal radiologist (JS). The modified and original Van Assche index were calculated and the changes between pre and post-therapy MRI were compared in clinical responders and non-responders.

Results

Thirty cases were included (12 females, median age 27 years). Clinical responders (n = 16) had a median modified Van Assche index of 9.6 (IQR 5.8–12.7) at baseline and 5.8 (IQR 3.5–8.5) at follow-up (p = 0.008). For clinical non-responders (n = 14), corresponding scores were 7.7 (IQR 5.8–13.5) vs. 8.2 (IQR 5.8–11.5) (p = 0.624).The original Van Assche index showed a significant decrease in post-treatment scores compared with pre-treatment scores in clinical responders (13.0 vs. 9.6, p = 0.011), whereas no significant differences were observed in non-responders. Looking at individual cases, 10 out of 16 responders (62%) had a decrease in the modified Van Assche index at follow-up, and 6/16 (38%) had an unchanged or increased index (Figure 1).

Figure 1. Modified van Assche index in clinical responders vs. non-responders.

Conclusion

This retrospective validation study showed a significant reduction in the modified Van Assche index in perianal CD patients who responded to anti-TNF treatment, whereas pre and post-treatment scores did not change in non-responders. This was, however, also true for the original Van Assche index and both indexes showed a comparable sensitivity to change. Further research is warranted to establish the modified Van Assche index’ clinical value.

Reference

1. Samaan MA, Puylaert CAJ, Levesque BG, et al. The development of a magnetic resonance imaging index for fistulising Crohn's disease. Aliment Pharmacol Ther 2017;46:516–28.