Dried Blood Assessment Equivalent to Drawn Blood Samples

A self-sampling method for therapeutic drug monitoring (TDM) of biologicals was developed that should enhance TDM implementation by patients with various autoimmune conditions.

Investigators at the Sanquin Blood Supply Foundation (Amsterdam, the Netherlands) used the rheumatoid arthritis treatment drug adalimumab to establish the feasibility of replacing drawn blood samples with dried blood spots obtained by finger prick.

Adalimumab is a TNF-inhibiting, anti-inflammatory medication. It binds to tumor necrosis factor-alpha (TNFalpha), which normally binds to TNFalpha receptors, leading to the inflammatory response of autoimmune diseases. By binding to TNFalpha, adalimumab reduces this inflammatory response. Because TNFalpha is also part of the immune system, which protects the body from infection, treatment with adalimumab may increase the risk of infections. For this reason the U.S. Food and Drug Administration issued a black box warning to doctors, which appears in the product labeling of adalimumab and other TNF-inhibiting drugs, instructing them to screen and monitor potential patients more carefully.

The investigators compared adalimumab and anti-adalimumab antibody (ADA) concentration measurements in dried blood spots (DBS) obtained from finger pricks with measurements in serum obtained via venipuncture, from 161 patients with rheumatic inflammatory diseases. Adalimumab and ADA concentration were assessed by ELISA and antigen binding test (ABT), respectively.

Results revealed that adalimumab and ADA concentrations obtained by the finger prick/DBS method correlated well with serum results from the same patient (correlation coefficient greater than 0.87). Interestingly, antibody concentrations (adalimumab, ADA, or total immunoglobulin G) in DBS from finger prick, but not albumin, were systematically lower compared to serum. Experiments on spiked blood samples demonstrated a quantitative recovery for all tested proteins in DBS, suggesting a slightly different protein composition of blood collected via finger prick versus venipuncture. Therefore, the investigators established a correction factor of approximately 1.2 to relate finger prick/DBS values to serum values.

"Easy home sampling at different time points will benefit patients and could help to prescribe biologics optimally," said senior author Dr. Karien Bloem, post-doctoral researcher in immunopathology at Sanquin Blood Supply Foundation.

The study was published in the August 9, 2017, online edition of the British Journal of Clinical Pharmacology.

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Sanquin Blood Supply Foundation