Dried Blood Spot (DBS) testing is a biosampling method that involves collecting a small volume of blood, typically from a finger or heel prick, onto specialized absorbent filter paper. This technique offers a less invasive and more logistically simple alternative to traditional venous blood draws. The filter paper acts as a stable matrix, allowing the blood sample to dry and preserve the analytes within it. This stability simplifies handling and transportation, expanding the reach of diagnostic testing to settings with limited resources.
Sample Collection and Processing
The process begins with a simple capillary blood draw using a sterile lancet, usually performed on the fingertip for adults or the heel for infants. Before the puncture, the collection site is often warmed to increase blood flow, and the area is cleaned with an alcohol swab and allowed to air dry. The first drop of blood is typically wiped away with a clean gauze to minimize contamination from tissue fluid.
A large, free-flowing drop of blood is allowed to form, and the specialized filter paper card is gently touched to the drop. Capillary action draws the blood into the paper matrix, which must completely saturate the designated circle to ensure a standardized sample volume. The finger must not touch the card, and multiple drops should not be layered, as this affects the test’s accuracy.
Once the required spots are filled, the card is air-dried face-up for a minimum of three to four hours, preferably overnight, at ambient temperature away from direct sunlight or heat. The drying process inactivates many pathogens, reducing the biohazard risk during handling and shipment. The dried card is then packaged with a desiccant packet in a low gas-permeability plastic bag to protect it from moisture during transit to the testing laboratory.
In the laboratory, technicians use a specialized hole punch to remove a small, uniform disk from the center of the dried blood spot. This disk represents a known, standardized volume of the original blood sample, which is essential for accurate quantitative analysis. The analytes are then extracted from the paper matrix using a solvent. The resulting liquid is analyzed using advanced techniques, such as tandem mass spectrometry or high-performance liquid chromatography, to precisely measure compound concentrations.
Primary Applications in Healthcare
The most widely recognized application of DBS testing is in worldwide newborn screening programs. Samples collected via a heel prick allow for the early detection of dozens of congenital and inherited metabolic disorders, such as phenylketonuria (PKU) and congenital hypothyroidism. Early identification of these conditions is paramount because prompt intervention can prevent severe neurological damage and long-term complications in infants.
DBS testing is also used for therapeutic drug monitoring (TDM) and pharmacokinetic studies. This involves measuring drug concentrations in a patient’s bloodstream to ensure the dosage is within the therapeutic window. The ability to collect samples remotely makes DBS practical for patients requiring frequent monitoring or participating in clinical trials.
The method is valuable for infectious disease surveillance, especially in remote or resource-limited regions. DBS samples are utilized to test for various infections, including HIV, Hepatitis C, and SARS-CoV-2 antibodies. The stability of the dried sample is beneficial for large-scale epidemiological studies, as it allows for simple collection and shipping from diverse geographic locations.
Operational Benefits Compared to Venous Blood Draws
DBS collection is significantly less invasive than traditional venipuncture, requiring only a small finger or heel prick. This minimal invasiveness makes the procedure far less painful and stressful, which is advantageous for pediatric patients, the elderly, and individuals with a strong fear of needles. It also eliminates the need for a trained phlebotomist to locate a suitable vein, simplifying the collection process.
A major logistical advantage of DBS is the inherent stability of the dried sample. Once dried, the blood spot can be stored and shipped at ambient room temperature, unlike liquid blood samples that require immediate processing and expensive cold-chain refrigeration. This stability reduces transportation costs and the risk of sample degradation, expanding testing access to areas far from central laboratories.
The simple collection process allows for decentralization outside of clinical settings, such as in patients’ homes or community health outreach programs. This flexibility improves patient convenience and compliance by circumventing the need to travel to a clinic or blood collection center. A limitation of DBS is that results can sometimes be affected by the patient’s hematocrit level (the volume percentage of red blood cells). Despite this, the convenience and accessibility of the method continue to drive its adoption as a reliable diagnostic alternative.