Invalid Specimens
Certain types of specimens are known to give erroneous laboratory results. In accordance with laboratory regulations, these cannot be tested and are termed invalid. This delays the screening of the newborn, and requires that the submitter repeat the collection procedure.
Simple Spot Check provides examples of unacceptable specimens. You will need Adobe Acrobat Reader to view Simple Spot Check. To download a free copy of Acrobat Reader, click here.
Causes of Invalid Specimens
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The New York State testing laboratory classifies unsuitable specimens into eight categories based on the following criteria:
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Invalid Specimens |
Possible Causes |
| Quantity of blood insufficient |
1) Filter paper circle incompletely filled or not saturated.
2) Blood applied with needle or capillary tube.
3) Contamination of surface of filter paper circle.
4) Failure to obtain any blood. |
| Blood spots appear scratched or abraded |
Blood applied improperly with capillary tube or by other means. |
| Blood spots wet or discolored |
Specimen not properly dried before mailing. |
| Blood spots appear supersaturated |
Excess blood applied (usually with capillary tube or needle). Blood applied to both sides of filter. |
| Blood spots appear diluted |
1) Puncture site squeezed or "milked" to expel blood.
2) Exposure of blood spots to direct heat.
3) Contamination of filter paper before or after blood collection by gloved or ungloved hands or by substances such as alcohol, feeding or antiseptic solutions, hand lotion or powder. |
| Blood spots exhibit "serum rings" |
1) Alcohol not wiped off puncture site before skin puncture is made.
2) Allowing filter paper to come in contact with alcohol, water, hand lotion, etc.
3) Squeezing the area around the puncture site excessively.
4) Drying the specimen improperly.
5) Applying blood to filter paper with a capillary tube. |
| Blood spots appear clotted or layered |
Touching the same filter paper circle to a blood drop several times. Filling the circle from both sides of the filter paper. |
| Specimen delivered to the laboratory more than 14 days after collection |
1) Specimen held at the hospital before mailing.
2) Delivery delayed by the post office or other delivery service. |
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