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Correspondence

Indian Pediatr 2015;52: 902-903

Effective Strategy for Newborn Screening for Congenital Hypothyroidism

 

Prakash Gambhir

Institute Birthright Genetic Clinic, Pune, Maharashtra, India.
Email: [email protected]

 


With reference to the recent publication [1] on screening of hypothyroidism, we wish to submit following observations:

Authors have reported that total number of patients under study was 1950 while the total as per the table is 1952. In text, authors state that there were 397 premature and 1551 full term neonates. This makes the total 1948! It is also remarkable that the male to female ratio is 0.53:1 (682 males to 1268 females).

Authors state that they could pick up one extra case with cord blood cut-off of 10 mg/mL but they had false positive rate of 20% in the bargain. Authors report that they repeated thyrotropin stimulating hormone (TSH) at 72 hours for screen positives, and those with rising trends were evaluated at day 5 and day 12. With this protocol a baby with congenital hypothyroidism with raised cord blood TSH with steady or little less TSH at 72 hours is likely to be missed. Guidelines by American Academy of Pediatrics [2] do not mention a rising trend but values above cut-off for repeat sample to be considered screen positive if first sample is an early sample [2].

With the study methodology, every 5th baby had to be called for repeat evaluation resulting into higher costs as well as unnecessary parental anxiety. This could have been easily avoided with first screen sample after 72 hours followed by recall of screen positives for confirmation. In case of premature babies, repeat sampling could have been done later (may be at 2 weeks) in view of delayed maturation of hypothalamus-pituitary-thyroid axis [2,3]. Authors also have not mentioned whether the hypothyroid newborn with cord blood thyroxine of 18 mU/L was preterm or the mother had thyrotoxicosis. Authors also should have stated whether the two hypothyroid babies picked up at 2 weeks had prematurity or any accompanying maternal condition.

The findings of this study once again stress the importance of sampling after the TSH surge is over and having a proper cut-off to minimize false positive rate. Sampling at 4 or 5 days followed by recall of screen positives for confirmatory test will involve sampling only twice as against 3 or 4 times as in this study. As cord blood TSH is known to have higher false positive rate, this strategy may increase the cost and parental anxiety [4,5].

References

1. Anand MR, Ramesh P, Nath D.  Congenital hypothyroidism screening with umbilical cord blood: Retrospective analysis. Indian Pediatr. 2015;52:435-6.

2. American Academy of Pediatrics, Susan R. Rose SR, MD, and the Section on Endocrinology and Committee on Genetics, American Thyroid Association, Brown RS, and the Public Health Committee, Lawson Wilkins Pediatric Endocrine Society. Update of newborn screening and therapy for congenital hypothyroidism. Available from: www.pediatrics.org/cgi/doi/10.1542/peds.2006-0915. Accessed June 14, 2015.

3. Bhatia V. Congenital hypothyroidism is not always permanent: Caveats to newborn thyroid screen interpretation. Indian Pediatr. 2010;47:753-4.

4. Gupta A, Srivastava S, Bhatnagar A. Cord blood thyroid stimulating hormone level – Interpretation in light of perinatal factors. Indian Pediatr. 2014;51:32-7.

5. Gambhir PS. Cord blood TSH for screening of hypothyroidism: Is it justified? Indian Pediatr. 2014;51:503.

 

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