Oral (15W154)

C – reactive protein predicts Low Trough Infliximab Concentrations in Patients who Lose Response to Infliximab

Author(s)

Marie P. Boyle, Alan C Moss, Aoibhlinn M. O’Toole, Adam S. Cheifetz

Department(s)/Institutions

Division of Gastroenterology, Beth Israel Deaconess Medical Center & Harvard Medical School, Boston, MA, USA

Introduction

Low serum infliximab (IFX) concentrations are associated with an increased risk of loss of response in IBD. Whether C-reactive protein (CRP) could be used to identify patients with low drug concentrations is unknown.

Aims/Background

The objective of this study was to evaluate the test characteristics of CRP in identifying low serum IFX concentrations.

Method

We measured serum IFX concentrations and CRP levels in patients who experienced symptom deterioration while on IFX (reactive cohort). Receiver operating characteristic (ROC) curves were used to determine the CRP concentration threshold that identified an IFX concentration <3 μg/mL at the time of loss of response. These CRP thresholds for IFX concentration <3 μg/mL were then tested in a separate validation cohort.

Results

We measured serum IFX concentrations and CRP levels in patients who experienced symptom deterioration while on IFX (reactive cohort). Receiver operating characteristic (ROC) curves were used to determine the CRP concentration threshold that identified an IFX concentration <3 μg/mL at the time of loss of response. These CRP thresholds for IFX concentration <3 μg/mL were then tested in a separate validation cohort.

Conclusions

CRP levels > 12mg/L exhibit a high specificity for identifying patients with IFX concentration < 3ug/mL. CRP may be a cost-effective alternative to identify patients with low concentrations of IFX at the time of, or at risk of, loss of response.