capillary blood sampling in serology and remote testing: benefits, guidelines and considerations

by Neoteryx Microsampling on Sep 20, 2021 9:00:00 AM

The human body contains an astonishing 60,000 miles of blood vessels. This intricate network includes three key types of vessels that play crucial roles in blood circulation: arteries, veins, and capillaries.

Among these, capillaries are particularly significant in modern microsampling techniques and are increasingly utilized in clinical, diagnostic, and research settings.

Capillary Blood: A Central Player in Modern Sampling

Capillaries are tiny blood vessels where oxygen and nutrients are exchanged for waste products between the blood and tissues. Because of this unique function, capillary blood contains a mixture of arterial and venous blood, making it particularly suitable for various types of blood analysis.

Although laboratory standards have traditionally relied on venous blood, capillary sampling is becoming more popular due to its practicality and versatility in different contexts, including serological studies and remote diagnostics.

Understanding How Capillary Sampling Is Used in Serology and Remote Testing

Capillary blood sampling started as a method for collecting blood from newborns whose veins are too small for traditional venous blood draws. The "heel stick" technique remains a standard practice in hospitals today.

Over time, the use of capillary sampling has expanded, allowing for remote testing related to chronic disease monitoring, viral serology, and more.

In particular, serology studies— which assess antibodies and immune responses—have increasingly adopted capillary blood sampling due to its feasibility for home collection.

During the COVID-19 pandemic, this method enabled major institutions, such as the NIH and Stanford University, to conduct remote seroprevalence studies without requiring in-person visits.

With straightforward finger-stick techniques and tools like the Mitra® device, which utilizes VAMS® technology, participants can easily collect blood drops at home.

They can then seal the samples in a dry format and mail them to laboratories for analysis. These self-managed microsampling kits offer a practical solution for decentralized research and diagnostics.

Understand the Clinical and Technical Guidelines for Capillary Blood Sampling

To ensure accurate results and maintain the integrity of samples, capillary blood collection must adhere to specific protocols:

• Correct Puncture Site Selection: Choose the puncture site—fingertip, upper arm, or heel—based on the subject's age and health condition.
• Disinfection and Site Preparation: Thoroughly cleanse the puncture area and warm it to enhance blood flow.
• Discard the First Drop: Wipe away the initial blood drop to minimize the risk of contamination.
  
• Avoid Milking or Scraping: These actions can lead to hemolysis, which compromises sample quality.
  
• Proper Labeling and Packaging: Ensure that every sample is correctly labeled and stored in approved specimen bags.
• Drying and Shipping: Dried blood samples can be transported without the need for cold-chain logistics, making them more convenient for field studies.

By following these guidelines, you can help reduce the risks of hemolysis, cross-contamination, or data loss due to sample degradation.

Evaluate the Pros and Cons of Capillary Blood Collection Methods

Benefits of Capillary Blood Collection:

• Minimal Invasiveness: Only a small finger stick is needed, eliminating the need for venipuncture needles.
• Patient Convenience: Minimizes the need for travel to clinics by allowing for self-collection at home.
• Remote and Decentralized Access: Ideal for populations in remote or underserved areas.
• Point-of-Care Testing: Capillary blood enables quick, on-site blood tests. Its crucial role was evident in the rapid diagnosis and management of the Ebola outbreak.
• Special Populations:  Suitable for children, elderly individuals, and patients with disabilities.
• Cost Efficiency: Eliminates the need for cold shipping and reduces storage costs.
• Ethical Research Practices: Reduces animal usage in preclinical studies by enabling repeated, low-volume sampling.

Limitations and Considerations:

• Sample Volume Restrictions: Only small volumes can be collected per site.
• Test Suitability: Not all assays are validated for use with capillary blood.
• Potential for Hemolysis: Improper technique may rupture blood cells.
• User Error in Self-Collection: Risk of contamination or labeling errors.
• Skin Reactions: Rare complications like calcified nodules or localized irritation.

Despite these limitations, capillary blood sampling remains a practical and increasingly preferred option for appropriate applications.

Comparing Capillary and Venous Blood in Serology Studies

While venous plasma has traditionally been considered the gold standard for serological tests, capillary blood has shown to produce comparable results in many assays. Although there may be variations in hemoglobin, hematocrit, and glucose levels, these differences typically do not affect the accuracy of the tests when proper protocols are followed.

Capillary blood has been effectively used to detect antibodies for viruses such as measles, influenza, and SARS-CoV-2. The key factor is ensuring that there is equivalence between capillary and venous samples for each specific assay.

Conclusion: Microsampling Is Redefining Blood Collection

Remote blood collection using capillary sampling techniques is changing the way blood is drawn, tested, and analyzed. With its unique combination of accessibility, comfort, and analytical reliability, capillary sampling is set to play a central role in the future of diagnostics and serology research.

As more studies demonstrate that capillary samples are equivalent to traditional methods and best practices become standardized, both researchers and clinicians can confidently adopt this modern technique. This approach helps to expand access, reduce costs, and improve patient engagement—one drop at a time.

Image Credits: iStock, Trajan, Neoteryx