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 in-patient visits for venous blood draws, with a healthcare professional collecting vials of wet blood that are sent to the lab for analysis.

The entire process is not only tedious, but labor-intensive. Remember, wet blood requires special storage and transportation procedures to keep the samples stable. This can be challenging and costly, especially when a patient undergoes 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 reduce the resources required for collection, shipping and analysis.

What is dried blood sampling and testing?

Dried blood spot or dried blood sampling (DBS) is an innovative sampling technique where small blood samples are blotted on an absorbent paper and allowed to dry for analysis. The concept was introduced in 1963 by Dr. Robert Guthrie, who discovered that capillary blood, obtained from pricking the finger or heel and blotted on a filter paper, could be used to screen for metabolic diseases in newborns.

What is the efficacy of dried blood testing?

Research conducted at Uppsala University, Sweden, showed that dried blood testing 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 are a way to provide patient-centric care. For DBS, only a small volume of blood needs to be collected, usually using a finger-prick method to draw a drop or two of capillary blood from the fingertip.

The DBS approach doesn't require a needle in 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.

DBS can be self-administered at home without professional help. Typically, the patient orders a home health kit, self-collects the blood sample, and mails it to the lab for analysis.

2. High-Quality Blood Samples

A recent advance on DBS testing as first conceived by Dr. Guthrie is a newer method called volumetric absorptive microsampling, or VAMS^®. The VAMS approach facilitates the collection of a very precise volume and high-quality blood sample. Mitra^® devices with VAMS technology can be used by patients to collect small blood samples, typically from a finger-prick, with relative ease.

These smaller samples are analyzed in the lab as dried blood microsamples, providing results that are typically concordant with or correlated 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. 

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. 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 patients who must submit to frequent blood draws for therapeutic drug monitoring or other medical interventions.

With dried blood testing, the quality of samples has been shown to be relatively high. Studies show that blood samples collected remotely by study participants using Mitra with VAMS can detect SARS-CoV-2 antibodies in those previously exposed to the virus.

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. 

Blood collection using Mitra with VAMS utilizes absorbent tips that are enclosed in plastic cartridges and placed in sealed pouches with drying desiccant for shipping. Since the blood on a Mitra device tip will dry after collection and remain stable at ambient temperatures, there is no need for 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 remote 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 using cold shipping from the patient's home to the lab.

Dried blood eliminates these challenges and restrictions, since blood collection can be done by the patient at home and the sample can be easily sent through the mail directly to the lab for testing. Mitra microsamples dry on the device tip and arrive at the lab as dried blood samples, ready for testing. After testing, the treating physician or clinical researcher receives the lab results, and can follow-up with the patient or trial subject remotely via telecommunications.