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HOSPITAL AUTHORITY CONVENTION 2016  Masterclasses

                                    M12.1 Diagnosis Before Birth: For Mothers and for Babies  10:45  Theatre 2

                                    Gestational Age Specific Thyroid Function Test Reference Intervals — Controversies and Solutions
                                    Tam WH
                                    Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Hong Kong

                                    Thyroid dysfunction is the second most common endocrine condition encountered in pregnancy. Overt hyper- or hypo-
                                    thyroidism is associated with adverse pregnancy outcomes such as miscarriage, intrauterine growth restriction, preterm
                                    delivery and pre-eclampsia. Subclinical hypothyroidism during pregnancy is also associated with impairment of fetal brain
                                    development and could result in lower IQ. However, there are still questions and controversies in screening for subclinical
                                    hypothyroidism and thyroid antibodies and their management.

                                    Thyroid hormone levels change during pregnancy related to the change in hCG level, increase in the demand and binding
                                    globulin. Most international guidelines advise to use trimester specific reference range for the interpretation of thyroid function
                                    test (TFT) during pregnancy. However, TFT reference ranges vary among different platform and populations. Diagnosis of
                                    subclinical thyroid dysfunction could be difficult and challenging.

                                    This presentation will cover preliminary work on the project of gestational age specific TFT for Hong Kong population for
                                    different platforms, highlight some local experience in the management of thyroid dysfunction in pregnancy illustrated with
                                    some case examples.

                                    M12.2 Diagnosis Before Birth: For Mothers and for Babies  10:45  Theatre 2

Wednesday, 4 May                    Non-invasive Prenatal Testing as Primary Screening for Down Syndrome
                                    Lo TK 1, Law LW 2
                                    1Department of Obstetrics and Gynecology, Princess Margaret Hospital, 2Department of Obstetrics and Gynaecology, Prince of
                                    Wales Hospital, Hong Kong

                                    The performance of non-invasive prenatal testing (NIPT) is superior to the Down screening methods currently in use for both
                                    high- and low-risk pregnancies. In terms of benefits and harms, NIPT as first-tier screening test is preferred. The concern
                                    over loss of benefits from current Down screening strategy after its replacement by NIPT is not substantiated. The ethical
                                    principles of equity and reproductive autonomy also favour NIPT for universal screening. Evidence from the US demonstrated
                                    that, from a social perspective, it’s cost effective to replace current Down screening strategies with NIPT if the cost of NIPT is
                                    no higher than USD453.1 A preliminary analysis showed that when the cost of NIPT is below USD300, current Down screening
                                    strategies in the Hospital Authority could potentially be replaced by NIPT without increasing the expense per case of trisomy
                                    21 diagnosed from a social perspective. As the price of NIPT is now down to USD300 and below, universal application of
                                    NIPT can be economically justified. In fact, it was recognised that NIPT could be offered below USD250 and yet the provider
                                    is already making a good profit from it.2 The use of NIPT as a primary screening test for all pregnant women is also endorsed
                                    by the International Society of Prenatal Diagnosis (ISPD).3

                                    In Hong Kong, the universal first trimester combined screening (FTS) using fetal ultrasonographic measurement of nuchal
                                    translucency and serum biochemical markers to detect common aneuploidies has implemented since 2010. However, since
                                    2011 when non-invasive prenatal testing (NIPT) for aneuploidy using cell-free DNA (cfDNA) in maternal plasma came into
                                    clinical use, this has resulted in tremendous changes in our prenatal counselling and testing. Although NIPT has a higher
                                    detection rate and lower false positive rate in detecting Down’s syndrome, the implementation as primary screening to replace
                                    the current system will lead to missing more other fetal chromosomal abnormalities and it is not cost-effective. The apparent
                                    benefit of reduction of miscarriage from avoiding invasive prenatal diagnostic procedures may have been overestimated
                                    as well. Instead of implementing as primary screening, incorporating NIPT into current universal screening strategy as
                                    the contingent screening will gain the benefit of improving the detection rate without missing other fetal chromosomal
                                    abnormalities, and is relatively cost-effective.

                                    References:

                                    1. Fairbrother G, Burigo J, Sharon T, Song K. Prenatal screening for fetal aneuploidies with cell-free DNA in the general
                                        pregnancy population: a cost-effectiveness analysis. J Matern Fetal Nenatal Med 2015; 29(7): 1160-4.

                                    2. Minear MA, Lewis C, Pradhan S, Chandrasekharan S. Global perspectives on clinical adoption of NIPT. Prenat Diagn 2015;
                                        35: 959-67.

                                    3. Benn P, Borrell A, Chiu RWK, Cuckle H, Dugoff L, Faas B, et al. Position statement from the chromosome abnormality
                                        screening committee on behalf of the board of the International Society for Prenatal Diagnosis. Prenat Diagn 2015; 35:
                                        725-34.

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