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Screening for congenital hypothyroidism. II. Clinical findings in infants with positive screening tests
Insights
This study on congenital hypothyroidism screening found that TSH analysis of newborn blood spots is effective. A TSH cutoff of 50 mU/L plasma could enable nationwide screening with a recall rate under 0.1%.
Area of Science:
- Endocrinology
- Neonatal Screening
- Public Health
Background:
- Congenital hypothyroidism (CH) screening is crucial for early intervention.
- Optimizing screening protocols is essential for effective nationwide programs.
Purpose of the Study:
- To evaluate TSH and T4 analysis on PKU blood samples for CH screening.
- To determine optimal conditions for a routine nationwide CH screening program.
Main Methods:
- Pilot screening of 20,000 infants in Stockholm using TSH and T4 on PKU filter paper blood samples.
- Analysis of true-positive and false-positive screening results, categorizing infants into groups based on TSH and T4 levels.
- Clinical evaluation using a hypothyroid index score.
Main Results:
- Seven infants had true-positive CH diagnoses (6 primary, 1 secondary).
- 153 infants had false-positive results, with varied isolated or combined TSH/T4 abnormalities.
- Clinical signs were unreliable for distinguishing true from false positives.
Conclusions:
- TSH analysis alone is recommended for nationwide CH screening.
- A plasma TSH cutoff of 50 mU/L is proposed.
- This approach is expected to yield a recall frequency below 0.1%.
Abstract:
In a pilot screening programme for congenital hypothyroidism, PKU filter paper blood samples from 20 000 infants born in Stockholm were analysed for TSH and T4 to identify optimal conditions for routine nationwide screening. Among 160 infants with positive screening tests, 7 infants (group I) had true-positive results, 6 had primary and one secondary hypothyroidism. The 153 infants with false-positive tests were divided into group II:74 infants with an isolated increased TSH level; group III: 71 infants with an isolated decreased T4 concentration; and group IV: 8 infants with increased TSH and decreased T4 levels. In group I the clinical signs and symptoms of hypothyroidism varied when the diagnosis was made at 3 weeks of age. The median hypothyroid index score was 8 (range 0--18). In groups II-IV most infants showed very few signs of hypothyroidism. The median hypothyroid index scores were 1, 1, and 0, respectively. Clinical findings were of little value in the individual case for distinguishing true from false positive screening tests. We suggest that nation-wide screening should be based on TSH analyses of PKU blood samples, with a cut-off level corresponding to 50 mU/l of plasma. Recall frequency will be less than 0.1%.