Assure prompt delivery to the screening laboratory. Do not accumulate specimens, as they may become too old for testing. If the specimen is improperly collected, the accuracy of the screening tests can be compromised. The blotter circles are not uniformly saturated with blood. Blood fixed by heat or age will not elute from the filter paper.
Specimen appears to be contaminated by a spill or a foreign substance.
Blood has been applied to both sides of the filter paper, or blood is supersaturated. Tissue fluid or serum has separated from the blood. Blood clots are present on the specimen. Uneven or multiple applications of blood to the filter paper. Blood spots appear scratched or abraded.