why use dried blood tests vs. wet blood tests?

Blood sampling is an invaluable part of clinical research, but blood collection methods and blood storage chains are resource-intensive and sometimes wasteful. Most traditional blood collection methods require clinic visits for venous blood draws, with a healthcare professional collecting vials of wet blood that are sent to the lab for analysis.

The entire blood draw and blood sample transport process is not only tedious, but labor-intensive. Remember, wet blood requires special storage and transportation procedures to keep the samples stable until they are analyzed in a lab. This can be challenging and costly, especially when a person must undergo frequent blood collection and testing for long term therapeutic drug monitoring. 

In an effort to simplify blood collection and testing, scientists have developed dried blood sampling methods that simplify the process and reduce the resources required for blood collection, shipping and analysis.

What is dried blood sampling and testing?

Dried blood spot (DBS) or dried blood sampling is an innovative blood collection technique where small blood samples are collected from a lanced fingertip or heel and the blood drops are blotted onto an absorbent paper and allowed to dry for analysis.

The DBS concept was introduced in 1963 by Dr. Robert Guthrie. Dr. Guthrie discovered that a few drops of capillary blood obtained from pricking the finger or heel and blotted onto DBS filter paper could be used to screen for metabolic diseases in newborns. The dried blood samples were stable at room temperature and didn't require cold shipping or handling while in transit to the laboratory for bioanalysis.

What is the efficacy of dried blood testing?

Research conducted at Uppsala University, Sweden, showed that dried blood testing in a lab doesn’t require chemical modifiers to stabilize specific analytes. The researchers evaluated recently collected dried blood spots and those preserved for 30 years in biobanks to determine 92 protein levels. Wet samples stored at -70°C were also evaluated.

The researchers found that the drying process had a negligible effect on the protein level in the blood samples and that dried samples had numerous advantages over wet samples.

4 Benefits of Using DBS vs. Wet Blood Sampling

Based on research studies, here is an overview of dried blood sampling and testing benefits:

1. Greater Comfort for Patients and Study Subjects

Dried blood sampling with remote collection devices can be used as a flexible and convenient way to provide patient-centric care in different settings. With dried blood sampling, only a small volume of blood needs to be collected, typically using a finger-prick method to collect a drop or two of capillary blood from the fingertip.

The DBS approach doesn't require a needle poked into a vein of the arm, so it is less painful or scary for kids and needle-phobic adults. Because the finger-prick method of blood collection is minimally invasive, the patient is less anxious, and the collection procedure is executed faster and more easily.

Blood collection using finger-stick sampling approach can be self-administered at home without professional help. Typically, the patient or study subject receives a sample collection kit that contains the sampling device and supplies. They use the enclosed lancet to prick their fingertip and self-collect the blood samples. After sample collection, they mail their samples to the lab where the samples will be processes and analyzed.

2. High-Quality Blood Samples

There is now a newer method of dried blood sampling that is an advance on the DBS method that was standardized by Dr. Guthrie. The newer method is called volumetric microsampling. One method is called volumetric absorptive microsampling, which is based on small sampling devices that are designed with VAMS^® technology.

VAMS technology makes it easy to collect a fixed-volume blood sample. The VAMS approach facilitates the collection of a very precise volume and high-quality blood sample, thanks to a small absorptive VAMS tip at the end of each microsampler in the device. Mitra^® devices with VAMS technology can be used by lay people to collect small blood samples, typically from a finger-prick, with relative ease.

These smaller blood samples will dry on the VAMS tip of the Mitra devices. Once the sampled devices arrive in the lab, the VAMS tips are processed following a DBS workflow. The samples are analyzed as dried blood microsamples, typically providing results that correlate to those of wet blood samples.

The ease and convenience of this approach is quite a change from traditional venipuncture blood draws, which involve a phlebotomist puncturing a vein in the patient's arm to draw several tubes of blood in one session, with each tube containing a blood volume of 5-10 mL.

With the VAMS approach, a much smaller volume of blood is collected — typically no more than 120 µL with each finger-stick sampling session.  

Another device that utilizes volumetric microsampling is the hemaPEN, which simultaneously collects four volumetrically identical capillary samples from a single finger-stick.

The hemaPEN contains four glass capillary tubes that draw the blood drops from one finger-stick into the device, and transfers four dried blood spot (DBS) samples onto four pre-punched DBA filter papers housed inside the device.

Each of the four blood spots is a precise 2.74 μL ± 5 % in volume.

Click the hemaPEN shut after sample collection, and the four DBS samples are locked inside it until lab processing.

An advantage of using dried blood testing is that it doesn't require large volumes of blood for accurate analysis. In most cases, there isn't a need to take large blood samples from patients for testing. This means that less blood is wasted, since a large portion of the wet blood collected in phlebotomy tubes goes unused in the lab. Further, repeated and large volume sampling is undesirable, especially for smaller patients or those who must submit to frequent blood draws for drug monitoring or other medical interventions.

With dried blood samples that were collected using newer volumetric microsampling technologies, the quality of samples has been shown to be relatively high. For example, studies show that blood microsamples collected remotely by study participants using Mitra with VAMS at home can be analyzed for detection of SARS-CoV-2 antibodies in those previously exposed to the virus. In another example, studies show that blood microsamples collected using the hemaPEN can be analyzed to accurately detect people's exposure to environmental toxins, such as per- and polyfluoroalkyl (PFAS) chemical substances. 

3. Easier Shipping

Wet blood must be transported refrigerated or frozen and must remain in cold storage to prevent bacterial growth. Strict regulations govern the transportation of liquid blood products from the collection point to the lab. Dried blood sample collection doesn't require cold shipping or cold storage. 

Since the blood in or on a volumetric microsampling device will dry after collection and remain stable at ambient temperatures, there is no need for cold shipping or cold storage. 

4. Facilitates Remote Testing

With traditional approaches to blood collection, phlebotomists or other health workers perform venous blood draws to collect wet blood samples, which requires in-person visits. With mobile phlebotomy, the phlebotomist needs to visit a patient at home to collect the blood. The procedure exposes both the patient and the phlebotomist to potential infection. Additionally, the tubes of wet blood must be transported from the patient's home to the lab using cold shipping.

Dried blood eliminates these challenges and restrictions, since blood collection can be performed at home by the patient or study subject themselves. The sample can then be easily sent through the mail directly to the lab for testing. Dried blood microsamples dry in transit and arrive at the lab as dried blood samples, ready for processing and analysis. After testing, the treating physician or clinical researcher can access the lab results and follow-up with the patient or research subject remotely via telecommunications.

Learn more about dried blood microsampling: