Abstract 1824: Clinical Evaluation of Self Obtained Capillary Blood and Dried Blood Spots for Cyclosporine C0 and C2 Monitoring in Transplant Recipients
Therapeutic drug monitoring of Cyclosporine (CsA) is an established procedure to maintain the blood drug levels within their respective narrow therapeutic ranges reducing the risk of toxicity and rejection in transplant recipients. CsA peak levels measured 2 h post-dose (C2) are more predictive for transplant rejection than basal levels (C0). However, the clinical application of C2-levels is hampered by the precise time of blood sampling. The aim of our study was to evaluate a new C0 and C2 self-obtained blood sampling procedure in transplant recipients using capillary blood or dried blood spots and the regularly taken venous blood samples to compare the CsA levels, CsA stability, and clinical practicability of the different procedures. 55 solid organ transplant recipients were instructed to single-handed sampling of capillary blood and dried blood spots by finger prick. EDTA-coated capillary blood collection systems and standardized filter paper were used. CsA was determined by turbulent flow chromatography coupled with LC-tandem mass spectrometry. The C0 and C2 levels from capillary blood collection systems (C0: 114.5 ±44.5; C2: 578.2 ±222.2) and capillary dried blood (C0: 175.4±137.7; C2: 743.1 ±368.1) significantly (p< 0.01) correlated with the drug levels of the venous blood samples (C0: 97.8 ±37.4; C2: 511.2 ±201.5). The correlation at C0 was: ρcap.-ven. = 0.749 and ρdried blood-ven = 0.432; at C2: ρcap.-ven = 0.861 and ρdried blood-ven = 0.711. The lower correlation between dried blood spots and venous blood was caused by CsA degradation in the dried blood spots from anticoagulated whole blood. However, we could completely avoid the degradation of CsA in dried blood spots by the use of EDTA- blood. The patients preferred the dried blood sampling because of the more simple procedure. In conclusion, we could demonstrate that C0 and C2 self-obtained blood sampling using EDTA-stabilized capillary and dried blood spots can be easily performed by transplant recipients resulting in clinically valid cyclosporine measurements. The self-obtained blood taking facilitates the accurate C2 monitoring and supports the early prevention of transplant rejection and of toxic effects of the immunosuppressant.
This work was supported by a grant from Novartis.