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P569. Clinical correlations of infliximab trough levels (IFX-TL) and antibodies to infliximab (ATI) in inflammatory bowel disease

M. Daperno1, A. Lavagna1, M. Fracchia1, C. Guiotto2, L. Germano2, C. Rigazio1, E. Ercole1, M. Migliardi2, R. Pellerito3, R. Rocca1, 1AO Ordine Mauriziano, Gastroenterology Unit, Torino, Italy, 2AO Ordine Mauriziano, Laboratory Unit, Torino, Italy, 3AO Ordine Mauriziano, Rheumatology Unit, Torino, Italy


Anti-TNF blockers (infliximab and adalimumab) are approved and used in the treatment of Crohn's disease (CD) and ulcerative colitis (UC).

Since higher drug trough levels were shown to be associated to better disease outcomes and anti-drug antibodies were associated to higher chances of adverse drug reactions, therapeutic algorithms based on drug monitoring combined with anti-drug antibodies detection were proposed.

Stability in time of drug trough levels and clinical implications of IFX-TL and ATI in routine practice are still matter of debate.


A consecutive series of inflammatory bowel disease (IBD) outpatients, undergoing regular infliximab i.v. dosing, was prospectively enrolled. Clinical strata considered were:

  • disease activity (remission under infliximab vs active disease despite treatment)
  • disease subtype (Crohn's disease vs ulcerative colitis)
  • concomitant medications (steroids/immunosuppressors vs none)
  • variations in time

All cases underwent blood sampling before planned infliximab infusions. Detailed disease and drug history was collected. Sera were stocked until analyses were carried out. A single ELISA test was selected for clinical-IFX-TL/ATI correlations analysis: Promonitor ® IFX Determination of Drug and Anti-drug Antibodies Concentration (Menarini, Italy) kit.


66 IBD patients (39 CD and 27 UC, and 46 with quiescent disease and 20 with active disease, respectively) were recruited.

Median IFX-TL were 3.17 µg/ml (range 0.00–32.0) and 1.55 µg/ml (range 0.00–26.8) in quiescent and active disease respectively (p = 0.315).

When considering Crohn's and ulcerative colitis patients, median IFX-TL were 1.87 and 3.33 µg/ml, respectively (p = 0.227).

When patients under concomitant steroid/immunosuppressive treatment or not were considered, median IFX-TL were 3.62 and 1.56 µg/ml, respectively (p = 0.021).

ATI were negative in all but 6 cases, no significant association to disease type, activity or co-treatment was found.

No significant association was found between IFX-TL and: body mass index, age, disease duration, IFX treatment duration, CRP levels.


Clinical implications of IFX-TL and ATI dosing are still matter of debate before they can be proposed for routine clinical practice. In this population only association between combination immunosuppressive and anti-TNF treatments resulted significantly associated to higher IFX-TL. Larger dataset are needed for appreciating potential clinical impact of IFX-TL and ATI dosing.