Master's in Genetic Counseling (MGC)
Collection and Handling of Specimens
The method for collecting specimens is relatively simple, but care must be taken to ensure that the sample is collected properly in order to avoid inaccurate test results.
Obtaining the Specimen
Warm the infant's foot for about 3 minutes with a moist towel (temperature no higher than 42°C). This helps to increase the blood flow through the heel area. Also, holding the infant's leg in a position lower than the heart will increase venous pressure.
Clean the infant's heel with 70% isopropyl alcohol. Wipe the excess alcohol off of the heel with a dry, sterile gauze. Alcohol residue remaining on the skin may dilute the specimen and adversely affect the test results.
Allow the heel to air dry.
Puncture the infant's heel with a sterile lancet having a tip no longer than 2.5mm. Perform the puncture on the most medial or lateral portion of the plantar surface of the heel. Cord blood is not a satisfactory specimen.
Wipe away the first drop of blood with a sterile gauze. This initial drop may contain tissue fluids which may dilute the specimen.
Allow the second drop to form by spontaneous free flow of blood.
Touch the drop of blood to the center of the filter paper circle. Completely fill each printed circle with a single application of blood. The blood should soak all the way through the paper so that the spots look similar on both sides. Apply the blood only to one side of the filter paper.
Elevate the infant's foot above the body. Wipe the puncture area with a sterile gauze and apply a bandage as needed.
Allow the specimen to air dry completely at room temperature. Place the filter paper on a level, non-absorbent surface for 3-4 hours. Do not stack the specimens or apply heat to them.
The dried filter paper should be sent to the laboratory within 24 hours after specimen collection. Do not batch specimens collected on separate days. All specimens should be submitted on the day of collection.
Areas for Caution
Avoid handling the blood collection card at the filter paper end before, during, or after collection. Oils from the skin may alter absorption of blood and contaminate the specimen.
Failure to dry any alcohol residue may dilute the specimen and have adverse effects on the test results.
Puncturing the heel on the posterior curvature will permit blood to flow away from the puncture. Proper spotting will then be difficult.
Do not lance on a previous puncture.
Milking or squeezing the puncture may cause hemolysis of the specimen and admixture of tissue fluids with the specimen.
Do not superimpose blood drops on top of each other. Layering can be a cause of unsatisfactory results.
Do no allow water, feeding formulas, antiseptic solutions, etc. to come in contact with the specimen.
Thoroughly air dry the specimen. Insufficient drying can adversely affect the test results. Hair dryers or other sources of heat should not be used to dry the specimens.
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