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P422 Patient-near Infliximab trough-level testing by a novel quantitative rapid test; the Quantum Blue Infliximab assay

Roseth A.*1, Lindsjô I.2, Malmstrøm G.-H.3

1Lovisenberg Hospital, Medicine, Oslo, Norway 2Lovisenberg Diakonale Hospital, Deparment Of Gastroenterology, Oslo, Norway 3UngerVetlesen Institute, Oslo, Norway

Background

Therapeutic drug monitoring (TDM) has become standard clinical practice and overwhelming clinical evidence indicates that dose-optimization improve clinical outcome by decreasing the risk for anti-drug-antibodies (ADA) and improves the efficacy of the drug itself. There is also another aspect for advocating TDM, that is improving the health economic aspect of these very expensive drugs. However, this has been hampered by the high cost of and the absence of a near patient testing.

Aims of the study: The study had two aspects; first is to correlate a CE -marked rapid test for IFX trough level, the Quantum Blue Infliximab test (QB-IFX) (BÜHLMANN Laboratories, AG, Basel, Switzerland) to an assay very similar to the Loeven assay. Secondly, to correlate the performance of such a test done by; A) a nurse and B) a trained laboratory person

Methods

The study comprised 64 pts with IBD receiving IFX treatment; 14 Remicade and 50 Remsina. At the day of infusion, blood for IFX-trough level was collected in addition to 3 ml serum for QB-IFX rapid test.

Part A: A nurse (IL) received one hour of “laboratory” training before running the QB-IFX under supervision of AR. The serum was diluted 10uL in 190 uL assay buffer and vortexed for 5 sec. 70uL was applied to the rapid test cassette and read after 15 min using the Q B reader.

Part B: The same procedure was followed by an experienced lab technician (GHM). In addition, 5 aliquots from three sera-levels was collected (3, 7 and 10ug/ml) and tested to establish CV for the upper and lower trough level values as well as for one high level value.

Results

The was a very good correlation between the QB-IFX rapid test and the laboratory ELISA test, r=0.90, p<0.001, the slope was 1.1. Furthermore, the correlation between the results obtained by the nurse and a skilled lab person was acceptable with r=0.92, p<0.001. The CV for the upper and lower trough level was 4.7 and 7.8% respectively. CV for the high level was 14.7%

Conclusion

This is the first study that documents a close correlation between a 15 min. rapid test for IFX trough level with that of an standard lab-test. We have shown that such a test can accurately be performed by a nurse. The CV for the three different serumlevels was way lower than expected for a lateral flow rapid test. This means that TDM now can be moved from a distant laboratory to the near patient facility like the infusion centre to ensure correct dosing in IBD and other patients on IFX treatment.

References:

[1] Moore, C., Corbett, G., & Moss, A. C. (2016). Systematic Review and Meta-Analysis: Serum Infliximab Levels During Maintenance Therapy and Outcomes in Inflammatory Bowel Disease. J of Crohn's & Colitis, 10(5), 619–625.