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P726 Trough levels of infliximab better correlate with combined mucosal and transmural healing than clinical remission in Korean patients with Crohn’s disease on infliximab maintenance therapy

E. H. Oh*1, A-R. Yoon2, S. H. Park3, J. Kim1, N. Ham1, E. M. Song1, S. W. Hwang1,2, S. H. Park1,2, D-H. Yang1, J-S. Byeon1, S-J. Myung1, S-K. Yang1,2, B. D. Ye1,2

1Asan Medical Center, Gastroenterology, Seoul, South Korea, 2Asan Medical Center, Inflammatory Bowel Disease Center, Seoul, South Korea, 3Asan Medical Center, Radiology, Seoul, South Korea

Background

Studies on correlations between trough levels of infliximab (TLIs) and levels of antibody to infliximab (ATI levels) with combined mucosal and transmural healing as well as clinical remission in Crohn’s disease (CD) in non-Caucasians are still lacking.

Methods

TLIs and ATI levels were measured using prospectively collected serum samples drawn from CD patients on infliximab (IFX) maintenance therapy for more than 1 year at Asan Medical Center, South Korea, from August 2017 to August 2018. We analysed correlations between TLIs/ATI levels and combined mucosal and transmural healing as well as clinical remission. TLIs/ATI levels according to concomitant immunomodulator use were also evaluated.

Results

This study included 629 serum samples drawn from 348 patients. Two hundred and thirty-six patients were males (67.8%). The median age at diagnosis of CD and at starting IFX was 21.0 years (interquartile range [IQR], 17.0–29.0) and 28.0 years (IQR, 22.0–35.0),, respectively. Clinical remission (Crohn’s disease activity index [CDAI] < 150) was observed in 81.9% (515/629 samples) and combined mucosal and transmural healing was observed in 29.5% (84/285 samples). TLIs differed significantly between two groups divided by a cut-off value of ATI level as 9 µg/ml-eq (2.541 µg/ml [IQR 1.193–4.598] in ATI-negative samples [n = 590 {93.8%}] vs. 0.004 µg/ml [IQR 0.001–0.021] in ATI-positive samples [n = 39 {6.2%}], p < 0.001). TLIs showed significant differences between groups with or without combined mucosal and transmural healing (3.765 µg/ml [IQR 1.807–5.203] vs. 1.554 µg/ml [IQR 0.416–3.952], p = 0.001) but not between groups with or without clinical remission (2.454 µg/ml [IQR 1.182–4.455] vs. 1.498 µg/ml [IQR 0.152–4.223], p = 0.126). There was no difference in TLIs and ATI levels according to concomitant immunomodulator use at the time of measuring TLIs/ATI levels, during induction period and continuously from induction period to the time of measuring TLIs/ATI levels (Table 1).

TLIs (µg/ml)ATI levels (µg/ml-eq)
Non-useUseNon-useUse
At the time of measuring TLIs/ATI levels2.537 (1.315–4.805)2.213 (0.708–4.310)0.001 (0.001–0.046)0.001 (0.001–0.101)
p = 0.331p = 0.273
During induction period2.351 (0.826–4.741)2.304 (0.910–4.356)0.001 (0.001–0.012)0.001 (0.001–0.118)
p = 0.225p = 0.524
Continuously from induction period to the time of measuring TLIs/ATI levels2.293 (0.826–4.741)2.396 (0.910–4.325)0.001 (0.001–0.067)0.001 (0.001–0.118)
p = 0.373p = 0.642
*Median (interquartile range)

TLIs/ATI levels according to concomitant immunomodulator use.

TLIs above 5.49, 7.16 and 9.04 µg/ml (area under the receiver-operating characteristic curve = 0.665) identified patients on deep healing with specificities of 85%, 90% and 95%, respectively.

Conclusion

TLIs better correlated with combined mucosal and transmural healing than clinical remission in Korean CD patients on IFX maintenance therapy. There was no difference in TLIs/ATI levels according to concomitant immunomodulator use.