2020 · Journal of pharmaceutical and biomedical analysis · paywalled
Volumetric Absorptive Microsampling (VAMS) for assaying immunosuppressants from venous whole blood by LC-MS/MS using a novel atmospheric pressure ionization probe (UniSpray™)
Paniagua-González et al.
The finding, in our words
The authors developed and validated a VAMS method for quantifying immunosuppressants from venous whole blood using LC-MS/MS with a novel UniSpray ionisation probe. This supports patient-centric microsampling for transplant recipients requiring therapeutic drug monitoring.
A paraphrase to the Library’s standard, never the abstract. The source is one link away and is always the authority.
In lung and renal transplant recipients, VAMS sampling with LC-MS/MS quantification of mycophenolic acid and tacrolimus showed good linearity and accuracy, and with a haematocrit-adjusted conversion formula achieved clinical agreement in most samples; tacrolimus did not require haematocrit correction. The approach is virtually painless and enables richer sampling for more accurate drug exposure estimates, supporting decentralised therapeutic drug monitoring.
In matched clinical samples from rheumatoid arthritis, VAMS and DBS showed strong agreement for methotrexate polyglutamates (slopes 0.95-1.07; bias within -4.21% to 0.36%; SRCC ≥ 0.969), with up to 100% of total MTXPG results within ±20% limits; capillary microsampling agreed closely with whole blood but differed from red blood cells, indicating matrix-specific differences that must be accounted for when interpreting against RBC-based reference values.
A systematic review found mixed economic evidence for microsampling in therapeutic drug monitoring; one study reported no cost reduction with DBS home-sampling, €688 versus €676, whilst another predicted savings up to 61%. The authors caution that more work is required to assess costs alongside clinical outcomes and optimise logistics for decentralised implementation.
Dried saliva collected with the Mitra device correlated strongly with wet saliva but poorly with plasma unbound and total concentrations, indicating it is not a reliable substitute for plasma in routine therapeutic drug monitoring of mycophenolic acid and its glucuronide metabolite. Capillary blood collected via VAMS remains a promising alternative for long term monitoring in paediatric patients.
The paper summarises that volumetric finger-prick self-sampling is suitable for monitoring immunosuppressants and biomarkers after kidney transplantation, but successful implementation requires careful design of the entire workflow, including patient training and method validation. This matters because it provides a real-world framework for moving critical monitoring from the clinic to the patient's home.