Re-testing

Occasionally the newborn screening test will need to be repeated. This may be purely due to the routine requirement, if for some reason the first test was done before the baby was 48 hours old. However, the test may also need to be repeated if the blood sample was inadequate or was contaminated in some way. This is because the testing for metabolic disorders is very sensitive.

Caregivers are generally aware of reasons for re-testing but they may not always be avoidable and there is always room for human error. Reasons the laboratory may ask for a re-test can include:

	The baby's foot was wet, or covered with creams or oils before the test.
	The circles on the card were not completely filled in with blood or not soaked completely through to the other side of the paper.
	The blood sample was contaminated by either excessive squeezing of the baby's foot (releasing other tissue fluids that mixed with the blood sample) or by the sample coming in contact with other fluids or chemicals such as water, urine, sprays, tea, coffee etc. This can happen if the card is placed on a bench top or someone touches the blood spots after it is taken.
	The caregiver used a felt tipped pen (rather than a ballpoint pen) to fill in the details on the card and the ink has leached into the blood sample.
	The blood sample was not adequately dried before it was sent to the laboratory, or the card was dried in an area that was not well ventilated (or in plastic), causing the growth of bacteria on the sample (invalidating the test).
	The sample was placed near a freshly painted or varnished area. (The fumes from organic solvents can affect the test).

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