Dried blood spot (DBS) testing is a microsampling method that involves collecting a small amount of whole blood, typically from a finger or heel prick, and drying it on a filter paper for analysis. This method was initially developed in the 1960s for screening phenylketonuria (PKU) in newborns. Over time, its utility expanded beyond initial applications, finding broader use in various diagnostic and monitoring contexts.
The Collection Process
The procedure for collecting a dried blood spot sample is straightforward and designed to be minimally invasive. It begins with cleansing the chosen collection site, usually a fingertip for adults or a heel for infants, to ensure cleanliness. A sterile lancet is then used to puncture the skin, creating a small opening for blood flow.
Once a blood droplet forms, it is carefully applied to pre-marked circles on a specialized filter paper card. Apply sufficient blood to fill each circle completely, ensuring saturation without layering. The card is then left to air dry completely at room temperature for several hours before further handling. After drying, the card can be labeled with patient information and sent to a laboratory for analysis.
Diverse Applications
Dried blood spot testing has found diverse applications in medical and public health domains. It remains a standard method for newborn screening programs, identifying inherited metabolic disorders like phenylketonuria and congenital hypothyroidism early in life. This allows for timely interventions that can prevent severe health complications.
The method is also used extensively for screening infectious diseases, including human immunodeficiency virus (HIV), hepatitis B, and hepatitis C. Its simplicity facilitates large-scale screening efforts, particularly in regions where traditional venous blood collection might be challenging. Furthermore, DBS testing is employed for therapeutic drug monitoring, allowing healthcare providers to assess drug levels to optimize dosage and ensure treatment effectiveness.
Benefits of the Method
DBS testing offers numerous advantages over conventional venous blood draws. Being minimally invasive, it causes less discomfort and anxiety for patients, especially for children or those with needle phobia. Its simple collection process contributes to cost-effectiveness, requiring fewer specialized personnel and less equipment than venipuncture.
DBS samples are convenient for storage and transportation, as they do not require refrigeration and remain stable at room temperature for extended periods. This stability simplifies logistics, particularly for samples from remote areas or those shipped long distances. The method also improves accessibility, enabling self-sampling or at-home testing, benefiting individuals in underserved regions or with mobility limitations.
Ensuring Accurate Results
While dried blood spot testing offers many practical advantages, ensuring the accuracy of quantitative results has been a focus of ongoing advancements. Factors such as varying blood droplet sizes and the hematocrit effect, where the proportion of red blood cells influences blood diffusion on filter paper, historically presented challenges. These variables could impact sample volume consistency.
Modern innovations in sampling technology have largely addressed these concerns, enhancing the reliability of DBS testing. Specialized collection devices are now available that ensure the collection of a precise and consistent blood volume, irrespective of individual blood characteristics. These advancements mitigate the influence of factors like hematocrit, allowing for more accurate and reproducible quantitative analyses.