Dried blood spot (DBS) technology, a very simple technique for collecting, shipping, and storing blood samples, is widely used in applications such as screening for metabolic and sickle cell disorders, and HIV and malarial infections. The method involves spotting 15 μL of blood from a finger or heel prick onto absorbent filter paper that is then shipped and stored at room temperature (Figure 1). For analysis, the blood spot is punched out of the filter paper and the blood is extracted using a solvent (typically methanol) containing an internal standard.
Although DBS has been in existence for almost 50 years, the technology could only be used to screen for the presence or absence of a particular marker—a simple yes or no answer. It could not be used to determine to what extent a marker is present because the analytical technologies were not sensitive enough to obtain reliable, quantitative data from such tiny blood samples.
It is for this reason that DBS has not been widely utilized within drug discovery and development process. However, recent advancements that have been made in the sensitivity of analytical technologies—mainly mass spectrometry and ultra-high-performance liquid chromatography—have overcome this limitation. As a result, there is heightened interest within the pharmaceutical industry to replace liquid blood sampling with DBS.
DBS sampling can offer enormous advantages over liquid blood or plasma in both preclinical and clinical studies. These advantages include, but are not limited to, a significant reduction in the volume of blood collected, a simplified process that does not require the need to centrifuge, sub-aliquot, freeze, and defrost samples (all of which can introduce errors in the analysis), improved safety with handling, shipping, and storage at room temperature, improved data quality, improved compound stability for drugs and their metabolites, and considerable cost savings.
The use of DBS in preclinical studies results in a fivefold reduction in the volume of blood collected, which has a significant impact on animal studies and data quality (Figure 2). The number of rodents needed for each study can be reduced by up to 75%, and because fewer animals are needed, the quantity of compound needed for testing is also greatly reduced. The quantity of compound required for animal studies is very important in the early stages of drug development when the synthesis of the compound has not yet been optimized and is costly, time-consuming, and difficult to achieve.
DBS sampling also contributes to the generation of higher quality data in pre-clinical studies because more time points can be added without the need for additional rodents and the technology allows for serial pharmacokinetic (PK) profiling. Serial PK profiling eliminates the variability between animals observed when using composite profiling and greatly improves the quality of the data. In addition, DBS allows for pre-clinical juvenile toxicology studies to be conducted in small animals where the availability of blood has always been a problem. These studies are always necessary and required by regulatory agencies in support of clinical pediatric studies.