Aims: An automated method for the measurement of blood tacrolimus on volumetric absorptive microsampling (VAMS) devices was developed. Materials & methods: VAMS devices prepared by the automated method were compared with those prepared by the existing manual method (n = 284; mean concentration: 8.0 μg/l; range: 0.6-18.1). Results: The performance of both methods was comparable. Passing-Bablok regression demonstrated an acceptable correlation (y = -0.449 + 1.06x). Bland-Altman analysis demonstrated acceptable agreement (mean bias: -0.007 μg/l; standard deviation: 1.536). Automation reduced operator touch time by 40 min (48-sample batch). Conclusion: Automated preparation of VAMS devices reduced touch time and improved process consistency, facilitating high-throughput testing and transformation of existing laboratory workflows. Automation did not improve precision for VAMS devices but did so for liquid blood samples.
Keywords: automation; chromatography; mass spectrometry; method development; microsampling; therapeutic drug monitoring.
After a kidney transplant, many patients take a drug called tacrolimus to help prevent their new kidney from being rejected. Blood levels of tacrolimus are checked regularly to ensure each patient is receiving the right dose. This means regular visits to the hospital for blood tests, which can be inconvenient and time-consuming for the patient. Microsampling devices are now available that would enable patients to collect blood from a finger prick sample, at home, and post it back to the lab for testing. However, to date, access to home sampling is limited because measuring tacrolimus from blood collected on a microsampling device relies on a manual laboratory process that is difficult to do and takes a long time. Measurement of tacrolimus from blood collected on a microsampling device can be successfully automated with a Gerstel MPS robot. The robot extracts the tacrolimus from the blood on the microsampling device and injects the resulting sample into a mass spectrometer for measurement. Two sets of microsamples were prepared. One set of samples was extracted by the robot and one set of VAMS samples was extracted manually. Tacrolimus was measured by mass spectrometry for both sets of samples and the results compared well. The automated method requires less operator input than the manual method, which will make it easier to measure large numbers of microsamples quickly and safely, increasing the number of patients who can benefit from the advantages of remote sampling.