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Analytical validation of Procise Dx POC analyser for therapeutic drug monitoring of infliximab

BACKGROUND-AIM Within the past 20 years the use of biologic drug infliximab (IFX) in inflammatory bowel disease (IBD) treatment has been an important step forward in improving disease course and keeping the inflammation at remission for a prolonged period of time. Therapeutic drug monitoring (TDM) of IFX using the point-of-care (POC) methods showed to be able to produce results fast enough to allow IFX dose adjustments prior to drug infusion. This study aimed to compare two POC tests, Procise IFX (Procise Dx) and Quantum Blue infliximab assay (Bühlmann Laboratories AG) used in University Hospital Osijek. METHODS Serum samples from 22 IBD patients on IFX maintenance therapy were collected immediately before drug infusion. Capillary blood was also collected from 6 IBD patients by finger prick using whole blood pipettes (Procise Dx). Analytical imprecision was assessed using the human serum sample obtained from a patient on IFX therapy with IFX concentration 5, 4 mg/L. For method comparison a Passing Bablok regression was used and for qualitative comparison weighted kappa statistics was obtained after stratification of results by therapeutic range (<3 mg/l, ≥3 to 7 mg/L, and ≥7 mg/L). RESULTS Within- and between-laboratory precision of Procise IFX assay was 3, 9% and 1, 4%, respectively. Passing Bablok regression analysis of IFX concentration in serum sample has showed proportional deviation between POC methods (y=0.416 (-0.654 to 1.279) + 0.753 (0.648 to 0.923)x). Good comparison has been observed for capillary blood measured using Procise IFX test and serum samples measured using Quantum Blue Infliximab assay (y=-2.732 (-4.315 to 1, 867) + 1.263 (0.278 to 1.566)x), although IFX concentration was lower in capillary blood. Classification of results according to therapeutic interval showed good agreement for serum samples as well as for serum and whole capillary blood measurements (κ=0.79 (0.59-0.999) and κ=0.80 (0.45-1.00), respectively). CONCLUSIONS Procise IFX assay showed good analytical performances. Because of proportional differences, two POC tests can’t be used interchangeably for longitudinal TDM of infliximab in IBD patients. The use of whole capillary blood for TDM of IFX should be evaluated in a larger number of subjects.

Validation, Point-of-care, biologic therapy, infliximab

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