Infants who are premature (i.e., less than 37 weeks gestation) or who are sick should have their first specimen collected for Newborn Screening when they are five to seven days old. Premature infants will often have a low thyroid-stimulating hormone (TSH) level and may screen positive for congenital hypothyroidism. However, on repeat specimens, results can be differentiated into false and true positives. Prematurity or illness in an infant being screened should be clearly indicated on the newborn screening specimen card.

The Ontario Newborn Screening Program (ONSP) can analyze heel-prick blood spots from infants who have had TPN (hyperalimentation) or antibiotics. However, levels of certain amino acids and organic acids can be elevated in these infants. In order to ensure the most accurate analysis, the administration of these therapies should be clearly indicated on the newborn screening specimen card.

Infants who are affected with one of the disorders screened for by the ONSP may be missed if they have had a recent blood transfusion. Normal levels of newborn screening analytes may be found in these cases because of the donor blood. Ideally, a specimen card should be completed before transfusion. If a baby has been transfused, this should be indicated on the screening requisition to allow appropriate screening test interpretation and follow-up.

Call the ministry INFOline at 1-866-532-3161
TTY: 1-800-387-5559

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