Published on March 25, 2019
Did you know that your blood spot sample could be denied for testing if not done properly? It is especially important to provide a quality sample with multiple tests being performed from each blood spot sample.
What Does a Proper Blood Spot Look Like?
An acceptable blood spot should:
- Be at least the size of the circle (1/4 inches in diameter, the same size as a regular pencil eraser) on the front of the filter paper
- Soak completely through to the back of the filter paper, so that the sample is at least the size of the circle on both the front and the back
- Not overlap with any other blood spots on the filter paper
Each test needs at least 2 good blood spots on the filter paper for the test to be run accurately; 4 good spots are needed in case a rerun is deemed necessary by the lab. Four spots are especially needed for the Magnesium Plus Elements blood spot panel.
What does an Unacceptable Blood Spot Look Like?
Some examples of blood spot samples that would be rejected are shown below.
Spots are too small
(do not completely fill the circle)
The blood spots did not completely penetrate filter paper- spots are large on the front, but do not soak through to the back
Spots are re-spotted on the same location (multiple blood spots stacked on top of each other) showing different drying rings and improper absorption
Spots soak through the back but are “marbled” in appearance because of repeated applications
A blood sample can also be rejected if the participant shut the card too soon and blood was leached from the filter paper to the card’s protective cover, leaving a diluted blood spot.
For Omega blood spot samples, there are two additional requirements.
- They must be processed within 28 days of the date the sample was collected (it is very important to send them in immediately after doing the test).
- The samples must be placed on the treated filter card provided for the Omega testing.
These cards may also have a slightly pinkish tinge on the filter paper (this stain is normal!), and may say “OMEGA” on the back of the card.
Tips to Get a Better Blood Spot Sample
Before collection, it may help to:
- Drink a large glass of water.
- Warm hands by running them under hot water, using a heating pad, or taking a shower.
- Raise your heart rate by going up a flight of stairs or doing jumping jacks. If you have limited mobility, try pumping your opposite arm up and down (like a bird) during collection.
At the time of collection, it may help to:
- Place the collection card below waist level. If you are able, collect standing up and place the collection card on a low table.
- Wipe the puncture point with gauze between samples to help prevent the wound from closing.
- Don’t squeeze too close to the puncture site, but right below, just above the knuckle. You can also massage your entire forearm, starting from your elbow.
- Allow the blood to well up on your finger tip, so that you have a single large drop, before touching it to the card.
- When in doubt, an extra blood spot can be applied to the filter paper outside of the circles provided, as long as the samples do not overlap.
What Happens if a Blood Spot Sample is Rejected?
If a participant sends in a blood spot sample that is determined to be insufficient, the participant will be sent an email notice based on the reason for rejection. A replacement blood spot test kit will be sent free of charge to the participant. As long as the new blood spot sample is collected within two months of the questionnaire answers, no other action is needed from the participant.
Good luck and happy bleeding!
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