Other Collection Methods

Although not the method of choice, specimens can be obtained by applying blood to the newborn screening card, which has been collected in sterile, anticoagulant-free capillary tubes. The capillary tube collection method may also apply to blood collected from other sources and transferred onto filter paper.

The use of anticoagulants should be avoided during the collection of the newborn screening sample. Ethylenediaminetetraacetic acid (EDTA) may cause interference with some laboratory tests.

Since heparin is a known inhibitor of the Polymerase Chain Reaction (PCR) it should be avoided as it may result in test failure in some circumstances.

Collection

• Using a fresh sterile, plain (additive-free) capillary tube for each circle to be filled on the blood spot collection card, collect the appropriate volume of blood (each of the five 11 mm circles requires approximately 75-100 uL) required for the newborn screen.
• Touch the tip of the capillary tube to the blood drop formed at the heel puncture site. Allow blood to flow into the tube by capillary action. Fill rates might be improved by holding the tube in a near horizontal position when touching to the blood drop. Collect enough blood to fill all the circles.

Application

• After filling the capillary tube, immediately apply a blood drop to the center of a single, preprinted circle on the filter paper, completely filling the circle. Waiting too long before application will allow cells and plasma to separate or the blood to clot.
• To avoid damaging the filter paper fibers, do not allow the capillary tube to touch the filter paper. Actions such as “colouring in” the circle, repeated dabbing around the circle, or any technique that might scratch, abrade, compress, or indent the paper should not be used.

Tips

• Do not reuse capillary tubes.
• Apply blood to only one side of the filter paper. Do not apply multiple blood drops to the same circle, since caking or heterogeneous spreading will occur and might adversely affect test results.
• After blood has been collected from the heel of the newborn, the foot should be elevated above the body, and a sterile gauze pad or cotton swab pressed against the puncture site until the bleeding stops.

Although not the method of choice, blood collected from needle puncture of the dorsal hand vein and its application directly onto the preprinted circles of the filter paper is possible. Blood should not be drawn from an extremity into which IV fluids (including blood) are being or have been infused unless appropriate measures are taken.

The routine practice of dorsal hand vein collection is discouraged for various reasons, including:

• Test results might be affected by blood from different vessel sources.
• Hand veins might be needed for IV fluids and/or medication administration.
• Venous sampling is more invasive than a heel stick.

Collection and application

• Select the appropriately sized winged blood collection set (butterfly).
• Remove or shorten catheter length so blood can flow freely onto the circle on the filter paper.
• Use standard pediatric venous collection procedures. Syringe collection of blood for application onto a blood spot collection card is not recommended as time delays may allow for clot formation and settling of cells, (since anticoagulants are not used).

Although not the method of choice, blood collected from umbilical catheters (venous or arterial) is acceptable in certain situations (e.g., sick or very low birth weight infants).

Collection and application

• As UACs or UVCs are often used to infuse medications, it is important that blood (2 to 2.5 cc [mL] depending on the specifications of the catheter) be drawn from the line in order to clean it before the blood is collected for screening purposes.
• After cleaning the line, collect blood in an anticoagulant-free syringe and immediately apply a single blood drop to each printed circle on the blood spot collection card. It is important to transfer the blood quickly to avoid blood clotting, which can invalidate the specimen for testing.