Page 42 - HA Convention 2016 [Abstracts (Day 2)]

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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