Therapeutic drug monitoring of tacrolimus with the dried blood spot method

In a preliminary investigation an assay for tacrolimus based on fingerprick sampling and consecutive application as a blood spot on sampling paper has been developed. The dried blood spot was analysed by HPLC-tandem mass spectrometry. The validated range was 1-30 microg/l. Intra- and inter-assay variability for precision and accuracy was <7.5% and 15%, respectively. Tacrolimus concentrations of 24 stable out patients were compared after both blood spot sampling and conventional venous sampling. Method agreement was investigated with the methods of Passing and Bablok and Bland Altman and proved suitable for clinical use. The dried blood spot method for tacrolimus seems promising for patient monitoring

Therapeutic drug monitoring of everolimus using the dried blood spot method in combination with liquid chromatography–mass spectrometry

An assay of everolimus based on finger prick sampling and consecutive application as a blood spot on sampling paper has been developed. We explored several methods [K. Hoogtanders, J. van der Heijden, M. Christiaans, P. Edelbroek, J. van Hooff, L. Stolk, J. Pharm. Biomed. Anal. 44 (2006) 658–664; A. Allanson, M. Cotton, J. Tettey, et al., J. Pharm. Biomed. Anal. 44 (2007) 963–969] and developed a new method, namely the impregnation of sampling paper with a solution of plasma–protein, formic acid and ammonium acetate, in combination with the extraction of the blood spot by filter filtration. This kind of sample preparation provides new possibilities for blood spot sampling especially if analytes are adsorbed to the paper. The dried blood spot was analysed using the HPLC–electrospray-tandem mass spectrometry method, with 32-desmethoxyrapamycin as the internal standard. The working range of our study was 2–30 μg/l. Within this range, intra-and inter-assay variability for precision and accuracy was <15%. Everolimus blood spot samples proved stable for 3 days at 60 °C and for 32 days at 4 °C. Everolimus concentrations of one stable out-patient were compared after both blood spot sampling and conventional venous sampling on various occasions. Results indicate that this new method is promising for therapeutic drug monitoring in stable renal transplant patients

Therapeutic drug monitoring of everolimus using the dried blood spot method in combination with liquid chromatography–mass spectrometry

An assay of everolimus based on finger prick sampling and consecutive application as a blood spot on sampling paper has been developed. We explored several methods [K. Hoogtanders, J. van der Heijden, M. Christiaans, P. Edelbroek, J. van Hooff, L. Stolk, J. Pharm. Biomed. Anal. 44 (2006) 658–664; A. Allanson, M. Cotton, J. Tettey, et al., J. Pharm. Biomed. Anal. 44 (2007) 963–969] and developed a new method, namely the impregnation of sampling paper with a solution of plasma–protein, formic acid and ammonium acetate, in combination with the extraction of the blood spot by filter filtration. This kind of sample preparation provides new possibilities for blood spot sampling especially if analytes are adsorbed to the paper. The dried blood spot was analysed using the HPLC–electrospray-tandem mass spectrometry method, with 32-desmethoxyrapamycin as the internal standard. The working range of our study was 2–30 μg/l. Within this range, intra-and inter-assay variability for precision and accuracy was <15%. Everolimus blood spot samples proved stable for 3 days at 60 °C and for 32 days at 4 °C. Everolimus concentrations of one stable out-patient were compared after both blood spot sampling and conventional venous sampling on various occasions. Results indicate that this new method is promising for therapeutic drug monitoring in stable renal transplant patients

Genotyping with a dried blood spot method: a useful technique for application in pharmacogenetics

Several commercial DNA isolation kits are available for extracting the genomic DNA from the ethylene diamine tetra-acetic acid (EDTA) whole blood samples. To obtain DNA from whole blood these DNA isolation procedures require quite some hands on time and are rather expensive. An alternative technique could be dried blood spot (DBS) sampling, with which DNA isolation is faster, cheaper and logistics are easier. We have developed a non-commercial DBS method and examined its performance in practice. DNA isolation from EDTA blood samples and made blood spots on filter paper from 106 renal transplant recipients were compared. Additionally, DNA isolation with a column method and two different DBS method was performed for 10 healthy volunteers and compared. Also DNA isolation with only capillary blood using both DBS methods from another 100 healthy volunteers has been investigated. Real-time PCR FRET assays for the CYP3A4 A-392G, CYP3A5 A6986G, ABCB1 C1236T, G2677T/A and C3435T polymorphisms were used and the melting curves of both DNA isolation methods were compared. In all cases DNA extracted with the column method corresponded completely with the results of the DNA isolated with the DBS procedure. Hence, DNA isolation from filter paper appears to be a useful alternative for the commercially available DNA isolation kits