Evaluation of point-of-care instrument for quantification of infliximab and adalimumab.

Introduction: Treatment with infliximab (IFX) and adalimumab (ADL) are used in a range of inflammatory diseases. Measurement of drug levels is warranted, but can be challenged by turn-around-times at the laboratories. Consequently, point-of-care testing (POCT) technology is becoming increasingly relevant. We evaluated the precision and comparability of results obtained with ProciseDx (Biosynex) when used in outpatient gastroenterology clinics monitoring IFX and ADL.

Materials and methods: In this prospective multi-center study, capillary and venous blood samples were collected by trained nurses from patients with inflammatory bowel disease on maintenance therapy with either IFX or ADL. Fourteen different nurses performed blood sampling and IFX measurements using ProciseDx on 64 patients, while 11 different nurses performed ADL measurements on 48 patients. Venous samples were sent to the laboratory for routine testing using Promonitor ELISA kit on a Triturus (Grifols).

Results: Across all patients and all sites, a variation of 18.9% and 11.4% was observed for IFX and ADL measurements, respectively. Peak variance was in the 5-10 mg/L IFX concentration range, while peak variance for ADL measurements was above 12 mg/L. Compared to the routine ELISA, the r-value was 0.82 for IFX with a mean total deviation of 2.10 mg/L (27.1%). For ADL, the r-value was 0.91 with a mean total deviation of 2.93 mg/L (39.7%).

Conclusion: We find the efficacy and accuracy of the ProciseDx acceptable, but when performed by non-laboratory personnel, the differences to routine measurements are considerable and could have a clinical impact. Clinical implementation would at least require reevaluation of the therapeutic intervals.