Background: 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) 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: 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; 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; iii) to characterize probands and co-twins by NGS analysis of a panel of candidate genes.
Method: 39 twin couples and four triplets discordant for CH at first screening (43 CH probands) were recruited for the study. The range of the long-term follow-up in the couples/triplets was 221 years. Pairwise concordance rate (PWCR) for CH by the first month of life and for 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 six co-twins resulted positive at re-screening and the PWCR for CH confirmed at birth was 14.3%. During the long-term follow-up a thyroid hypofunction was observed in four co-twins and L-thyroxine treatment was started at the age of 2 mo, 9 mo, 12 years. The PWCR for thyroid hypofunction among couples discordant at screening was 21.3%. The systematic NGS analysis revealed variations consistent with the observed phenotype in 50% of concordant and 44% of discordant couples. Most of the discordant MZ cases remain unexplained by NGS analyses.
Conclusion: These results confirm the importance of the re-screening at 24 weeks of life in twins, the possible benefit of a long-term follow-up also in co-twin with negative test at screening and re-screening, and the need of further studies in order to uncover the largely unexplained pathogenesis of CH.
Funding: This work was supported by Ministry of Health Grant n. RF2010-2309484.
01 Oct 2015 - 03 Oct 2015