Liquid chromatography-mass spectrometry measurement of tacrolimus in finger-prick samples compared with venous whole blood samples

Abstract

Background Finger-prick sampling is an alternative strategy for monitoring immunosuppressive drug concentrations that could be useful in reducing outpatient visits. We investigated the correlation between venous and finger-prick samples in a group of adult thoracic transplant patients. Methods Blood samples ( n = 65) for the measurement of whole blood tacrolimus were collected from adult heart ( n = 18) and lung transplant ( n = 20) recipients receiving tacrolimus-based immunosuppressive therapy and a finger-prick sample was taken at the same time. Results Between-batch assay imprecision (coefficient of variation [CV], %) for the last 12 months ( n = 270) at concentrations of 3.5, 6.9 and 13.9 μg/L was 8.0%, 5.4% and 5.2%, respectively. Passing and Bablok regression analysis between finger-prick and venous blood showed finger-prick tacrolimus = 1.02 (venous blood tacrolimus) −0.06. Bland–Altman analysis showed good agreement with a bias of 0.114 μg/L and 95% limits of agreement from −1.0 to 1.2 μg/L. Conclusions The liquid chromatography mass spectrometry methodology that we have developed has the potential to allow patients or their carers to collect finger-prick blood samples at home and send them to the laboratory using the routine mail service. We believe that finger-prick blood sampling has an important role to play in the care of transplant patients receiving immunosuppressive drugs, including tacrolimus.