Clinical performance of volumetric finger-prick sampling for the monitoring of tacrolimus, creatinine and haemoglobin in kidney transplant recipients

Abstract

Aims Finger‐prick sampling has emerged as an attractive tool for therapeutic drug monitoring and associated diagnostics. We aimed to validate the clinical performance of using two volumetric devices (Capitainer® qDBS and Mitra®) for monitoring tacrolimus, creatinine and haemoglobin in kidney transplant (KTx) recipients. Secondarily, we evaluated potential differences between finger‐prick sampling performed by healthcare professionals vs . self‐sampling, and differences between the two devices. Methods We compared finger‐prick and venous sampling in three settings: microsampling performed by healthcare personnel, self‐sampling under supervision, unsupervised self‐sampling. The finger‐prick samples were analysed with adapted methods and results compared to routine method analysis of the venous blood samples. Results Twenty‐five KTx recipients completed the main study and 12 KTx recipients completed a post hoc validation study. For tacrolimus measurements and predicted area under the curve, the proportions within ±20% difference were 79%–96% for Capitainer and 77%–95% for Mitra. For creatinine and haemoglobin, the proportions within ±15% were 92%–100% and 93%–100% for Capitainer and 79%–96% and 67%–92% for Mitra, respectively. Comparing sampling situations, the success rate was consistent for Capitainer (92%–96%), whereas Mitra showed 72%–88% and 52%–72% success rates with samples collected by healthcare personnel and the patients themselves. Conclusions Capitainer and Mitra are technically feasible for measuring tacrolimus, creatinine and haemoglobin. In the context of self‐sampling, Capitainer maintained consistent sampling success and analytical quality. Implementing volumetric finger‐prick self‐sampling for the monitoring of tacrolimus, creatinine and haemoglobin may simplify and improve the follow‐up of KTx recipients.