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Age-dependent cutoff values in screening newborns for hypothyroidism.
John A Lott1, Marlinda Sardovia-Iyer, Karen S Speakman
1The Ohio Department of Health Newborn Screening Laboratory, Columbus, OH 43201, USA. lott.1@osu.edu
Clinical Biochemistry
|August 27, 2004
Summary
Newborn screening for hypothyroidism should be performed after 48 hours of age. Age-specific cutoff values for thyroid-stimulating hormone (TSH) improve the accuracy of identifying at-risk infants.
Area of Science:
- Biochemistry
- Pediatrics
- Endocrinology
Background:
- Congenital hypothyroidism screening is crucial for infant neurodevelopment.
- Thyroid-stimulating hormone (TSH) is a primary screening marker, with thyroxine (T4) used for confirmation.
- Establishing age-specific reference values is essential for accurate newborn screening.
Purpose of the Study:
- To develop age-related cutoff values for TSH and T4.
- To create an algorithm for classifying infants into low, moderate, and high risk for hypothyroidism.
- To optimize newborn screening protocols based on infant age.
Main Methods:
- Utilized time-resolved fluoroimmunoassay for TSH and T4 analysis.
- Developed a conservative screening algorithm with a TSH cutoff of >=20 microIU/ml for initial identification.
- Collected data from 161,244 newborns screened in 2002.
Main Results:
- Identified 8,035 infants with TSH values >=20 microIU/ml.
- Observed that TSH cutoff values decrease as infant age increases.
- Demonstrated the need for multiple cutoff values based on postnatal age.
Conclusions:
- Testing infants younger than 24 hours is not recommended due to unreliable TSH levels.
- Routine TSH and T4 testing should be performed at or after 48 hours of age.
- Risk stratification (low, moderate, high) requires follow-up testing and clinical evaluation for moderate and high-risk infants.