Organ transplant rejection occurs when the immune system attacks the transplanted organ. To prevent rejection, transplant-patients are given immunosuppressant drugs which can suppress the immune system from attacking the transplanted organ. Patients who have had a kidney-transplant take immunosuppressant drugs such as tacrolimus, but the dosage must be closely monitored through regular blood tests to avoid complications like organ failure and kidney damage. The current practice at Nottingham University Hospitals NHS Trust is that kidney-transplant patients being monitored for tacrolimus have regular blood samples taken by venepuncture (vein), and the samples are sent to the laboratory to be measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS), a technique used in chemistry to identify and quantify substances in a sample. Patients will also often have their blood-creatinine measured to get an idea of kidney health. Visits to the GP/hospital for this type of blood collection can be disruptive to a patient's daily life and stretches resources of the NHS. An alternative blood sample collection process involves the use of a hand-held blood collecting device called a Mitra device, designed to allow patients to collect samples at home through a finger-prick and send them by post for analysis. This method is especially beneficial for those who find hospital visits challenging or venepuncture painful.

This study aims to develop an LC-MS/MS method for measurement of tacrolimus and creatinine, using finger-prick samples collected on the Mitra device. To do this, kidney-transplant patients who are having routine venepuncture to measure tacrolimus and creatinine will simultaneously have a finger-prick sample collected using the Mitra device. Both the venepuncture sample and finger-prick samples will be analysed using existing LC-MS/MS technology to determine tacrolimus and creatinine values. The LC-MS/MS analysis method for the finger-prick samples collected using the Mitra device will be optimised and then results obtained using this method will be compared to the results obtained from venepuncture-collected samples to ensure consistency of results. Agreement of results between the two analysis methods will confirm the suitability of LC-MS/MS method for the measurement of tacrolimus and creatinine using samples collected using the Mitra device.

Inclusion Criteria:

• Patients attending renal clinic who are receiving immunosuppressant treatment (tacrolimus) and require regular monitoring.

Exclusion Criteria:

• No exclusion criteria

Patients attending renal clinic who are receiving immunosuppressant treatment (tacrolimus) and require regular monitoring.