Therapeutic drug monitoring of immunosuppressants is indispensable for therapy following organ transplantation. Cyclosporin A, tacrolimus, sirolimus und everolimus are the most common drugs used to prevent organ rejection.

Cyclosporin A and Tacrolimus block the cellular signal transduction by inhibiting the enzyme calcineurin which is involved in the immune response. Sirolimus and its derivative Everolimus have a similar suppressive effect on the immune system by inhibiting another enzyme of the intracellular signal transduction called mTOR (mammalian target of rapamycin).

The compensation of matrix effects plays a key role in the diagnostic analysis of immunosuppressants from a complex matrix such as whole blood. Here, matrix effects manifest as ion suppression which causes the measurement of incorrect values. These errors cannot be detected easily; the consequence are incorrect diagnostic statements.

Through optimised sample preparation the Chromsystems kit significantly reduces matrix effects. Isotopically labelled internal standards ensure the effective compensation of ion suppression. The analysis produces robust, precise and reproducible results. Manual sample preparation is reduced to a simple and effective protein precipitation. Subsequently, analytes are concentrated ONLINE on the trap column and potentially interfering matrix effects are separated. A six-port-valve connects the trap column to the analytical column. The use of multilevel calibrators (6PLUS1®) adds to the precision of results.