ELISA Measures Infliximab Drug Levels

There is strong evidence that one enzyme-linked immunosorbent assay (ELISA) yields more consistent quantitative and qualitative results when measuring adalimumab and infliximab levels, according to a new study.

Currently, rheumatologists use different ELISA assays to measure infliximab levels and infliximab anti-drug antibodies. Some tests are academically developed and others are commercial. Because infliximab and adalimumab drug levels and anti-drug antibodies are assessed using a variety of techniques, results cannot accurately be compared for clinical purposes, state the authors, led by Lara Valor MD, PhD, of the Department of Rheumatology at Gregorio Marañón University General Hospital in Madrid, Spain.

“To date unfortunately, there are neither gold standards nor guidelines available to monitor these drugs,” state the authors.

There are discrepancies between assays in part due to the fact that anti-tumor necrosis factor (TNF) agents such as infliximab and adalimumab are complex protein molecules.

They suggest that sample manipulation, assay control, reagent stability, processing, storage and the use of different calibration standards “could compromise the specificity, sensitivity and reproducibility of the assays which in turn may cloud associations between drug therapy and clinical response.”[[{"type":"media","view_mode":"media_crop","fid":"42614","attributes":{"alt":"©Maltsev Semion/Shutterstock.com","class":"media-image media-image-right","id":"media_crop_913819796405","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"4630","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"font-size: 13.008px; line-height: 1.538em; float: right;","title":"","typeof":"foaf:Image"}}]]

Recent studies show that the presence of antibodies against infliximab and adalimumab seems to correlate with low drug levels, which leads to less efficacy and subsequent adverse effects.  However, the presence of anti-drug antibodies does not fully explain the lack or loss of response to treatment, they noted.

The authors set out to test two infliximab and adalimumab ELISA versions for drug levels and anti-drug antibodies in three highly qualified rheumatology and immunology laboratories. Blood samples were collected from 48 rheumatoid arthritis patients, 24 patients taking infliximab and 24 patients taking adalimumab.

They found an interlaboratory agreement with Promonitor IFX R1 and R2 was poor for drug levels of both drugs, but there was a high agreement for Promonitor IFX and Anti-IFX for both drugs. A comparison between the two ELISA tests in each laboratory resulted in systematically higher values in Promonitor IFX and Anti-IFX than in Promonitor IFX R1 and R2.

The Promonitor IFX and Anti-IFX ELISA test has a substantially reduced number of error-prone steps, they noted, which cut the test procedure time by more than half (2.5 hours vs. 6 hours).

Qualitative measurements in Promonitor IFX and Anti-IFX produced better agreement, the authors stated, which “may be important when developing international standards to achieve uniform measurement in terms of developing guidelines in personalized patient management.”

References:

Valor L., Hernández-Flórez D., et al.

"Agreement in assessment of infliximab and adalimumab levels in rheumatoid arthritis: interlaboratory and interassay comparison."

Clin Exp Rheumatol. 2015 Sep-Oct;33(5):617-23. Epub 2015 Aug 27.