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* = Presenting author

P590 Therapeutic drug monitoring is a new tool for improving the care of patients treated by anti-tumour necrosis factor-alpha: Does this apply to children with inflammatory bowel diseases?

M. Chavannes*1, P. Jantchou1, F. Gervais1, R. Robitaille2, V. Marchand1, C. Deslandres3

1Sainte Justine University Hospital, Paediatric Gastroenterology, Montreal, Canada, 2Hôpital Maisonneuve Rosemont, Biochemistry, Montreal, Canada, 3Sainte Justine University Hospital, Montreal, Canada

Background

Infliximab (IFX) was proven effective in treatment of inflammatory bowel disease (IBD) in both children and adults. However, there is a significant number of patients who lose clinical response. Therapeutic drug monitoring (TDM) was shown to correlate with clinical response, mucosal healing, and better control of disease. Few studies demonstrate the same benefits in children. Some studies suggest that perhaps target blood level of IFX should be higher in children than in adults. Therefore, our objective was to review our experience of TDM in children with IBD treated with IFX.

Methods

This was a single-centre retrospective cohort study. The primary objective was to assess the blood level of IFX in children aged 5–18 years during the maintenance period. The secondary objectives were to correlate the levels with clinical response and to assess the proportion of patients in which a proactive dose adjustment approach has been taken. Patients were included if they had at least 1 blood level of IFX between June 2014 and November 2015. We collected trough levels and biochemical markers drawn a maximum of 2 weeks before the IFX level. Clinical assessments were based on patients self-report at the time of IFX infusion, graded on a 3-point scale (well, moderately well, and unwell). The physician global assessment was also recorded if done within 4 weeks of the IFX level.

Results

During the study period, 231 children were receiving IFX. Amongst them, 165 children had at least 1 IFX dosage. We present the preliminary analysis of the first 70 patients (61% male) who had 176 IFX levels. Further, 37% of patients were on combination therapy, the majority being with methotrexate (65.3%). IFX was started with a mean delay of 19 weeks from diagnosis (Range 0–130.6 weeks) at a dose of 5 to 10 mg/kg, depending on disease severity. There were 127 trough levels with a mean level of 4.95 ug/mL (range 0.01–14.4). The median IFX levels were comparable between males and female. Levels were sub-therapeutic in 46% of them, and supra-therapeutic in 24%. Clinical status as reported by patients did not correlate with infliximab levels.

Figure 1. Correlation between IFX level and patient reported outcome.

Conclusion

Of our IFX treated patients, 71% had at least 1 IFX dosage, mainly during maintenance. Despite adequate treatment, nearly 50% were sub-therapeutic, and the majority of these patients reported feeling well. Therefore, monitoring drug levels of IFX is mandatory in the management of IBD.