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

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 fingerprick 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.