In a recent article, Gupta, et al. [1] reported an important
aspect of thyroid metabolism which has great impact on neonatal
screening strategy for congenital hypothy-roidism. Prime consideration
for a newborn screening program is the cost effectiveness of the
exercise; the main determinants of which are the incidence of the
disorder, cost of the test as well as the false positive rate.
Authors quote that incidence of congenital
hypothyroidism in India detected by neonatal screening is 1:2500 to
1:2800 [2]. However, it is much more common according to recent reports.
Authors have not quoted a more recent study [3] which has reported the
incidence of congenital hypothyroidism as 1:1700. The ICMR multricentric
study [4] covering about 100,000 neonates found the disorder to be
occurring with even greater frequency of 1:900 in Tamilnadu and 1:1131
overall. Other published reports (quoted in the paper) - as well as the
authors, own data also shows the incidence to be nearer to 1:1000 than
1:2500 [1,5] .
Authors rightly say that perinatal factors affect the
cord blood thyroid stimulating hormone (TSH) level. They feel that
corrections should be designed to give due consideration to perinatal
factors in order to interpret TSH levels. It will be very difficult to
design and validate such corrections. Instead, it is advisable to adopt
the time- tested approach of screening by heel prick sampling once the
TSH surge is over. Blood sampling on day 3 or later is also performed
when multianalyte screening is undertaken.
We opine that congenital hypothyroidism – a
preventable cause of mental retardation – occurs with significant
frequency in India, and a neonatal screening program at national level
is the need of the hour. Dry blood sample collected by heel prick after
day 3 or day 4 of life is better strategy for neonatal screening as it
may avoid false positives because of perinatal factors. This may reduce
unnecessary parental anxiety and costs.
References
1. Gupta A, Srivastava S, Bhatnagar A. Cord blood
thyroid stimulating hormone level – interpretation in light of perinatal
factors. Indian Pediatr. 2014;51:32-7.
2. Desai MP, Colaco MP, Ajgaonkar AR, Mahadik CV, Vas
FE, Rege VV, et al. Neonatal screening for congenital
hypothyroidism in a developing country: problems and strategies. Indian
J Pediatr. 1987;54:571-81.
3. Devi ARR, Naushad SM. Newborn Screening in India.
Indian J Pediatr. 2004;71:157-60.
4. ICMR releases results of study on Congenital
Hypothyroidism. March 15, 2013. Chennaionline News. Mht. Available from:
http://news.chennaionline.com/chennai/ICMR-releasesresults-of-study-on-Congenital-Hypothyroidism
/58cca920 -765d-492b - 8fd3 - 9b34a8ac 2351.col. Accessed February
16, 2014.
5. Manglik AK, Chatterjee N, Ghosh G. Umbilical cord blood TSH levels
in term neonates: A screening tool for congenital hypothyroidism. Indian
Pediatr. 2005;42:1029-32.