CTF Structured Abstract: Congenital Hypothyroidism

Canadian Task Force on Preventive Health Care

Structured Abstract

Screening for Congenital Hypothyroidism

Prepared by Marie-Dominique Beaulieu, MD, MSc, FCFP, Department of Family Medicine, University of Montreal

These recommendations were finalized by the Task Force in January 1994

Objective
Burden of Suffering
Options
Outcomes

Evidence
Values
Benefits, Harms, and Costs
Recommendations

Validation
Sponsors
Selected References

Objective

To make recommendations for screening Canadian newborn infants for congenital hypothyroidism. This updates a 1990 Canadian Task Force report.

Burden of Suffering

The incidence of hypothyroidism ranges between 1 in 4,000 to 1 in 3,500 live births and can be as high as 1 in 141 live births among infants with Down Syndrome. Before screening was available, the age at diagnosis ranged from 1 week to 5 years or more. The intelligence quotient of 65% of patients with congenital hypothyroidism was below 85 (borderline mental retardation), and in 19% it was below 15 (profound mental retardation). Children whose mothers ingested iodides, propylthiouracil or radioactive iodide or had circulating antithyroid antibodies are at high risk for congenital hypothyroidism.

Options

Screening is done with dried blood samples tested at 3 to 6 days using either thyroid-stimulating hormone (TSH) tests followed by thyroxine (T4) in borderline cases or T4 testing done first. Treatment includes restoration and maintenance of normal thyroid levels.

Outcomes

Sensitivity and positive predictive values of the screening tests and recall rates.

Evidence

MEDLINE was searched for 1989 - 1993 using the keywords congenital hypothyroidism with screening and prevention and control. Only original articles were included.

Recommendations were graded as:

A Good evidence to support the recommendation that the condition be specifically considered in a PHE.

B Fair evidence to support the recommendation that the condition be specifically considered in a PHE.

C Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.

D Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

E Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

Quality of evidence was rated according to 5 levels:

I Evidence from at least 1 properly randomized controlled trial (RCT).

II-1 Evidence from well-designed controlled trials without randomization.

II-2 Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.

II-3 Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.

III Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.

Values

The 13-member Task Force of experts in family medicine, geriatric medicine, pediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.

Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993. Consensus was reached on final recommendations.

Benefits, Harms, and Costs

Dried blood collected on filter paper 3 to 6 days after birth and tested for TSH with confirmation of either normal or borderline results using T4 testing has a sensitivity of 95%. Initial testing with T4 has a recall rate of 1.1% and a positive predictive value of 2.4%.

65% of infants with untreated congenital hypothyroidism have an IQ of < 85 (borderline functioning or lower) and in 19% it is below 15. Eight cohort studies showed that affected infants who were identified and treated had mean IQs >100 and did not differ from control infants. Treated infants did not differ from controls on developmental scales. One of the studies showed that IQ was within normal values for treated infants but marginally lower than for infants in the control group (105 vs 110); these results continued to up to 12 years follow-up.

Screening and early treatment dramatically decrease the morbidity associated with congenital hypothyroidism. The fact that most hypothyroid infants identified at birth by screening have intellectual and psychomotor development in the normal range constitutes a dramatic improvement over the outcomes in children previously diagnosed later in life.

Recommendations

Recommendation grade [A, B, C, D, E] and level of evidence [I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations in support of individual recommendations are identified in the guideline text.

Good evidence exists to screen all newborn infants during the first week of life using routine TSH tests followed by T4 tests, if necessary [A, II-2]. Care must be taken to include children born at home or discharged early.

Validation

This report was externally peer reviewed. The 1989 U. S. Preventive Services Task Force also recommended universal screening of all newborn infants.

Selected References

Source Document

Beaulieu M.D. Screening for congenital hypothyroidism. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994;190-4.

Other

Canadian Task Force on the Periodic Health Examination: Periodic health examination, 1990 update: 1 Early detection of hyperthyroidism and hypothyroidism in adults and screening of newborns for congenital hypothyroidism. Can Med Assoc J. 1990;142:955-61.

Link to Full Text of this review

Link to Summary Table of Recommendations of this review

Link to Selected References list of this review

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A	Good evidence to support the recommendation that the condition be specifically considered in a PHE.
B	Fair evidence to support the recommendation that the condition be specifically considered in a PHE.
C	Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.
D	Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.
E	Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

I	Evidence from at least 1 properly randomized controlled trial (RCT).
II-1	Evidence from well-designed controlled trials without randomization.
II-2	Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.
II-3	Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.
III	Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.