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Poster presentations: Clinical: Therapy and Observation 2020

P465 Therapeutic drug monitoring in Crohn’s disease patients, a comparison between homogeneous mobility shift assay and point of care method

G. Bodini1, M.G. Demarzo1, A. Djahandideh1, I. Baldissarro1, E. Savarino2, V. Savarino3, A. Jain4, P.M. Risso3, E.G. Giannini3

1Gastroenterology Unit- Department of Internal Medicine, University of Genoa, Genoa, Italy, 2Department of Surgery- Oncology and Gastroenterology, University of Padua, Padua, Italy, 3Department of Internal Medicine, University of Genoa, Genoa, Italy, 4Department of Research and Development, Prometheus Laboratories Inc., San Diego, USA

Background

Therapeutic Drug Monitoring (TDM) is a useful tool to help physicians managing patients with Inflammatory Bowel Disease treated with anti-tumour necrosis factor (TNF) drugs. Different techniques are available to evaluate serum drug concentration (TL), However, these techniques are time-consuming. A point-of-care (POC) method has been proposed to evaluate drug TL and overcome the limitations inherent to other methodologies. Our aim was to evaluate the capability of POC to discriminate between IBD relapse and remission and to evaluate the concordance of drug TL measured with POC and HMSA

Methods

We analysed with Quantum BlueÒ (Buhlmann Laboratories AG, Schonenbuch, Switzerland) (POC) 200 Adalimumab (ADA) and 200 Infliximab serum samples of 46 Crohn’s disease (CD) patients previously assessed with HMSA. Blood samples were drawn at standardised time points during anti-TNF treatment (2, 6, and every 8 weeks), before anti-TNF administration. Disease activity was assessed by the Harvey–Bradshaw Index (HBI, remission defined by HBI<5).

Results

We evaluated 46 CD patients responders to anti-TNF induction with ADA (n = 25, 54.3%) and IFX (n = 21, 45.6%) with a median follow-up of 83 weeks (range 16–144 weeks). At week 16, median ADA TL of patients in remission were significantly higher as compared with patients in disease relapse using both HMSA [12.7 μg/ml (range, 8.9–23.6 μg/ml) vs. 6.6 μg/ml (range, 0.7–9.6 μg/ml), p = 0.0001] and POC [17.8 μg/ml (range 7.6–35.0 μg/ml) vs. 9.8 μg/ml (range 5.8–11.4 μg/ml), p = 0.0003]. The concordance between the two different techniques has been assessed as 0.76 by Choen Kappa. Considering IFX TL, patients in remission had higher serum drug concentration using both HMSA [7.0 μg/ml (range, 0.0–21.8 μg/ml)] and POC [6.2 μg/ml (range 0.4–14.3 μg/ml)] as compared with patients who experienced disease relapse [HMSA, 0.1 μg/ml (range, 0.0–4.1 μg/ml), p = 0.019; POC, 0.45 μg/ml (range 0.4–3.3 μg/ml), p = 0.0072]. The concordance between the two different test for IFX TL was 0.81. We obtained similar results at the end of follow-up: median ADA TL was higher in remission than in disease relapse patients using both HMSA and POC [p = 0.001 and p = 0.0012] with a concordance of 0.75. Median IFX TL was higher in remission than in disease relapse patients using both HMSA and POC (p = 0.13 and p = 0.25) with a concordance of 0.70.

Conclusion

Both POC and HMSA are TL tests able to differentiate relapse and remission in IBD patients. The association between anti-TNF TL and disease status (remission/relapse) was better in ADA-treated patients rather than patients treated with IFX. Finally, we demonstrated a good concordance between HMSA and POC. Anti-drug antibody concentrations while available on HMSA were not available on POC