Background: A high risk of congenital hypothyroidism (CH) has been documented in multiple pregnancies. Over the years special screening procedures for preterm and twin babies (re-screening at 24 weeks of life) have been adopted by many screening laboratories worldwide. However, no extensive studies have been performed to verify how many co-twins with negative test at first screening (35 days of life) become positive at re-screening, and the utility of a long-term follow-up also in co-twin with negative test at screening and re-screening.
Objective and hypotheses: The aims of this study were: i) to estimate the concordance rate for CH by the first month of life in twin couples/triplets discordant for CH at the first screening and ii) to verify whether a long-term follow-up of co-twins with negative test at screening and re-screening may be useful to verify the occurrence of thyroid hypofunction in these children during development.
Method: Twenty-four twin couples and two triplets discordant for CH at first screening (26 CH probands) were recruited for the study. The range of the long-term follow-up in the couples/triplets was 3 months18 years. Pairwise concordance rate (PWCR), for CH by the first month of life and for the occurrence of thyroid hypofunction during development, was calculated as the proportion of concordant pairs over the sum of concordant and discordant pairs.
Results: Among the couples/triplets discordant at first screening two co-twins resulted positive at re-screening. Therefore, the PWCR for CH was 7.1%. During the long-term follow-up a thyroid hypofunction was observed in three co-twins and a treatment with L-thyroxine was started at the age of 2 months, 9 months, and 12 years. The PWCR for thyroid hypofunction among couples discordant at screening was 11.7%.
Conclusion: These preliminary results confirm the importance of the re-screening at 24 weeks of life in twins, and the possible benefit of a long-term follow-up also in co-twin with negative test at screening and re-screening.
18 Sep 2014 - 20 Sep 2014