Utilising Volumetric Absorptive Microsampling (VAMS) Technology to Monitor Tacrolimus and Creatinine

Tacrolimus is a medicine given to try and stop rejection of a new kidney after transplant surgery. If too much taken the kidney may be damaged. If not enough taken, the risk of rejection is increased. Creatinine is a waste product made by the muscles and is normally removed from the body by the kidneys. If kidney function gets worse, the creatinine level in the blood goes up and means the new new kidney is not working properly. It is important to monitor levels of tacrolimus and creatinine regularly, to keep the kidney as healthy as possible. Regular monitoring also aids with balancing the amount of tacrolimus that patients need to take.

The COVID-19 pandemic led to changes in the delivery of transplant services. One such changes was a move to the use of point-of-care, and at home devices.

The study involves the set-up a new method in an NHS laboratory to test tacrolimus and creatinine levels in blood collected in the normal blood tubes and to compare the results with this new collection device, to see if the results are the same.

If the results match, patients will continue to collect a blood sample using the new devices and send it to the laboratory. This will save both patients and the NHS time and money as they will not have to travel to a hospital to have their bloods taken.

A minimum of 50 adult renal transplant patients (\>18 years old) taking tacrolimus as an immunosuppressant will be recruited when attending their routine outpatient follow up appointment, or if selected as eligible by the Renal Consultants and transplant nurses. Written consent will be obtained from all participants.

Patients attending blood clinic to have their routine blood samples taken will also have a finger prick and a small amount of blood (10µl) will be collected by volumetric absorptive micro sampling (VAMS) using the Mitra® device (Neoteryx), according to manufacturer's instructions. Two venous blood samples will be collected from the patients by venepuncture by trained phlebotomists/nurses. A 4ml EDTA and a 4ml serum gel sample (to measure tacrolimus and renal function as part of routine care). Tacrolimus and creatinine are measured in venous blood samples as part of routine patient care therefore these will be processed as normal, and results reported. The paired capillary samples collected using the Mitra® device will be batched and run when appropriate by liquid chromatography-mass spectrometry (LC-MS/MS). Mitra® devices will be stored at -20 degree Celsius, prior to analysis.

Venous EDTA whole blood samples (collected by venepuncture) and capillary whole blood samples (collected by VAMS®) will be analysed for tacrolimus using a validated LC-MS/MS assay in routine clinical use in the lab using the Waters ACQUITY UPLC system and Xevo TQD MS. Capillary whole blood samples (collected by VAMS®) and serum samples will be analysed for creatinine using an LC-MS/MS method which will be developed in house. For the method comparison, serum samples (collected by venepuncture) will be analysed for creatinine using an enzymatic method on the Roche platform. All sample analysis will be performed in an ISO 15189 accredited laboratory.

Eligibility Criteria:
Inclusion Criteria:

* Post renal transplant patients taking tacrolimus
* having regular bloods taken for tacrolimus and renal function testing.
* Patients must be taking tacrolimus as part of their immunosuppressive regimen.
* They must be over 18 years of age

Exclusion Criteria:

* Patients under the age of 18 (the study is for adults only).
* Vulnerable adults who are deemed unable to give consent themselves - If applicable, this can be assessed using the Trust clinical tool 'Assessment of Mental Capacity'.