Dried blood spot testing procedure

Dried Blood Spot (DBS) testing is a simple and minimally invasive method. It collects, stores, and transports small quantities of blood on filter paper for laboratory analysis. It is widely used for newborn screening, monitoring chronic diseases, infectious disease testing.

Here’s the procedure of Dried Blood Spot (DBS) testing.

Preparation before testing

• Sterile lancet (single-use).
• Alcohol swabs.
• Gauze or cotton pads.
• Filter paper (specialized DBS cards, e.g., Whatman 903 or equivalent).
• Gloves (to prevent contamination).
• Bandages (optional for after the collection).

Sample Collection

1. Clean the puncture site with an alcohol swab and allow it to air dry.
2. Use a sterile lancet to puncture the skin.
3. Wipe away the first drop of blood with gauze to avoid contamination.
4. Allow next drops of blood to form naturally. Do not squeeze the puncture site, as this can dilute the blood with interstitial fluid.

• Application to Filter Paper:
  1. Gently touch the blood drop to the filter paper, ensuring the blood completely saturates the circle or target area.
  2. Avoid overlapping blood spots or spreading the blood beyond the marked areas.
  3. Fill each circle completely, typically requiring 3–5 spots depending on the test requirements.

Drying

• Place the Dried blood spot card flat , ensuring the blood spots are exposed to air.
• Allow the blood spots to air dry for at least 3–4 hours at room temperature.
• Avoid direct sunlight, high humidity, or contamination during drying.

Storage and Transport

• Place the dried card in a breathable bag with a desiccant and humidity indicator.
• Store at room temperature, away from extreme heat, moisture, or light.
• Pack the DBS cards securely and transfer to the laboratory after the specified guidelines for biohazard materials.

Analysis

• The laboratory punches out a small section of the blood spot for testing.
• Techniques like ELISA, PCR, HPLC, mass spectrometry, or immunoassays are used depending on the test type (e.g., metabolic screening, infectious diseases).

Dried blood spot testing

• Newborn screening for metabolic disorders (e.g., PKU, hypothyroidism).
• Monitoring infectious diseases (e.g., HIV, hepatitis).
• Drug level monitoring (e.g., antiretroviral therapy, antibiotics).
• Genetic testing or biomarkers.

Key Considerations

Ensure proper collection to avoid common issues like:

• Insufficient blood volume.
• Hemolysis due to excessive squeezing.
• Contamination or improper drying.