Dried blood spot methods in therapeutic drug monitoring: methods, assays, and pitfalls.

This article reviews dried blood spot (DBS) sampling in therapeutic drug monitoring. The DBS method involves applying whole blood obtained via a fingerprick to a sampling paper. After drying and transportation, the blood spot is extracted and analyzed in the laboratory. Assays of many medicines in DBS have already been reported in the literature and are reviewed here. The technique involved in and factors that may influence the accuracy and reproducibility of DBS methods are also discussed. DBS sampling ultimately seems to be a useful technique for therapeutic drug monitoring that could have many advantages in comparison with conventional venous sampling. However, its benefits must be weighed against the degree of potential errors introduced via the sampling method; there is evidently a need for more standardization, quality assurance, basic research, and assay development.

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.