Signs of congenital hypothyroidism are minimal at birth. Congenital hypothyroidism has an incidence of 1:3600–1:5000 in the United States.
This measurement is used as a confirmatory test or in conjunction with neonatal T4, for infants with positive T4 screens or low blood serum T4 levels, and for screening in all U.S. states. See newborn screening in Chapter 11 for more information.
Newborn screen: <20 mIU/mL by third day of life
TSH surges at birth, rising within 30 minutes of life and peaking at a level of 70 mIU/mL within the first 24 hours. It declines within the first 3 days of life and reaches adult levels by the first week to 10 days of life.
Cleanse the infant’s heel with an antiseptic and puncture with a sterile disposable lancet. Collect this whole blood specimen 3–7 days after birth.
If bleeding is slow, it helps to hold the leg dependent for a short time before blotting the blood on the filter paper. Do not use pipettes or capillary tubes to collect blood.
Completely fill in the circles on the filter paper. This can best be done by placing one side of the filter paper against the infant’s heel and watching for the blood to appear on the front side of the paper and to fill the circle completely. The filter paper is a special filter paper card obtained from the laboratory.
Air-dry the filter paper for 1 hour, fill in all information, and send to the laboratory immediately. Do not expose samples to extreme heat or light.
Pretest Patient Care
Inform the parents about the test purpose and method of specimen collection.
See Patient Care for Thyroid Testing.
See Chapter 1 guidelines for safe, effective, informed pretest care.
Posttest Patient Care
Be prepared to counsel parents regarding steps to take if the TSH test is abnormal and type of treatment required. See newborn screening in Chapter 11. Review test results; report and record findings. Modify the nursing care plan as needed.
See Chapter 1 guidelines for safe, effective, informed posttest care.