Capillary blood microsampling to determine serum biopharmaceutical concentration: Mitra® microsampler vs dried blood spot

Aim: For assessment of concentrations of biopharmaceuticals, for example, therapeutic drug monitoring, dried blood sampling of capillary blood is a convenient alternative to traditional venepuncture sampling. We investigated an alternative to dried blood spot collection on filter paper: sampling capillary blood using the Mitra((R)) microsampler. Materials and Methods: Therapeutic monoclonal antibodies were spiked in whole blood, sampled using filter paper and Mitra microsampler and concentrations measured using specific ELISAs. Results: Good recoveries of adalimumab, infliximab, ustekinumab, vedolizumab, tocilizumab, natalizumab and rituximab were found up to 1 month of storage at room temperature, averaging 95.2% for the Mitra microsampler and 92.9% for Whatman((R)) paper. Both hemoglobin and potassium yield satisfactory estimates for the volume of the cellular fraction of blood samples in combination with the Mitra microsampler. Conclusion: We established practical protocols for the estimation of serum/plasma concentrations of therapeutic antibodies via capillary blood microsampling.