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Cord blood thyroxine and thyroid stimulating hormone screening for congenital hypothyroidism: how useful are they?
1Paediatric Department, Tawam Hospital, Al Ain, Abu Dhabi, United Arab Emirates. drjdhardy@yahoo.com
Insights
Cord blood screening for free thyroxine (FT4) is less effective for congenital hypothyroidism (CH) than thyroid stimulating hormone (TSH). Capillary TSH testing remains the most sensitive method for newborn screening.
Area of Science:
- Neonatal screening
- Endocrinology
- Public health
Background:
- Limited literature exists on cord blood screening for FT4 compared to heel prick tests.
- Hospitals in the UAE have utilized cord blood FT4 and TSH screening for years.
- The national screening program for congenital hypothyroidism (CH) in the UAE adopted capillary TSH testing in 1998.
Purpose of the Study:
- To assess and compare the diagnostic utility of cord blood screening for FT4 and TSH in newborns.
- To evaluate the effectiveness of different newborn screening methods for CH.
Main Methods:
- Retrospective review of infants diagnosed with CH between January 1998 and June 2004.
- Analysis of infants who underwent both cord blood screening (FT4 or TSH) and capillary TSH screening on days 4-5.
Main Results:
- Cord blood FT4 screening missed over half of CH cases in Tawam Hospital.
- Cord blood TSH screening detected 6 out of 8 CH cases in Oasis Hospital, with a recall rate of 1 in 23.
- Cord FT4 identified only the most severe CH cases, while cord TSH showed higher sensitivity but also a recall rate.
Conclusions:
- Cord blood FT4 screening is insufficient for comprehensive CH detection.
- Cord blood TSH screening is more sensitive than cord FT4 but less sensitive than capillary TSH testing.
- Capillary TSH dried blood spot testing on days 3-5 is the most sensitive and recommended method for newborn CH screening.
Aim:
To determine and compare the usefulness of cord blood screening for free thyroxine (FT4) and thyroid stimulating hormone (TSH).
Background:
There is a vast amount of literature on capillary heel prick screening tests, but relatively little on cord blood testing particularly FT4. For a decade all infants born at Tawam Hospital had cord blood FT4 and at Oasis Hospital cord TSH measured through the hospital-based screening programme. On January 1st 1998, the national screening programme (NSP) for congenital hypothyroidism (CH) in the United Arab Emirates (UAE) started using capillary TSH measurement (Delfia method). Since then newborns in both hospitals have been screened both ways, i.e. cord blood and capillary blood screening.
Methods:
We reviewed retrospectively all infants born from January 1998 until the end of June 2004 with CH who had double screening: cord FT4 or TSH and 4th-5th day TSH screening.
Results:
Thirteen infants (one in 1,778) had CH in Tawam Hospital. In six of these the cord blood FT4 was low (<9.1 pm/l) (0.73 ng/dl) and in seven the cord blood FT4 was normal, i.e., over half were missed. Eight infants (one in 1,198) had CH in the Oasis Hospital. Cord blood TSH was high in six of them (>13 IU/l) and two were normal. Cord FT4 detected the most severe cases, but missed most others. Cord TSH detected six out of eight cases, but there was a recall rate of one in 23.
Conclusions And Recommendations:
Cord FT4 identifies only infants with severe CH. Cord TSH is more sensitive than cord FT4 screening. Capillary TSH dried blood spot testing on the 3rd-5th day is the most sensitive method.
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