Dried blood samples can support monitoring of infliximab concentrations in patients with inflammatory bowel disease: A clinical validation

AIMS: Therapeutic drug monitoring (TDM) can optimize the efficacy of infliximab (IFX) in patients with inflammatory bowel disease (IBD). Because of the delay between blood samples taken at trough and availability of results, dose adjustments can only be carried out at the next infusion, typically 8 weeks later. Dried blood samples (DBS) performed at home to measure IFX concentrations can reduce the time to adapt dose/dosing interval. Here, we aimed to validate the clinical application of DBS for IFX in IBD patients and to evaluate the feasibility of home sampling. METHODS: DBS results from 40 IBD patients on IFX treatment were compared to serum sample results at trough, peak, and 3–5 weeks after IFX infusion. Subsequently, patients performed DBS home sampling one week before the next IFX infusion. These were compared to serum concentrations as predicted by Bayesian analysis. RESULTS: IFX concentrations from finger prick and venous puncture correlate well. DBS IFX concentrations showed high correlation with serum IFX concentrations (Spearman correlation: ≥0.965), without bias. Passing‐Bablok regression for IFX concentrations in DBS from home sampling also showed no bias (intercept: 1.02 mg L(−1) (95% CI −1.77–2.04 mg L(−1)), slope: 0.82 (95% CI 0.63–1.40)), with reasonable correlation (Spearman correlation: 0.671). CONCLUSIONS: Timely adjustment of IFX dose/dosing interval can be facilitated by IFX concentration measurement in home‐sampled DBS. DBS is a reliable method to measure IFX and can be used to predict IFX trough concentrations.