Anita Sik Yau Kan

Whole-genome array CGH evaluation for replacing prenatal karyotyping in Hong Kong.

Objective To evaluate the effectiveness of whole-genome array comparative genomic hybridization (aCGH) in prenatal diagnosis in Hong Kong. Methods Array CGH was performed on 220 samples recruited prospectively as the first-tier test study. In addition 150 prenatal samples with abnormal fetal ultrasound findings found to have normal karyotypes were analyzed as a ‘further-test’ study using NimbleGen CGX-135K oligonucleotide arrays. Results Array CGH findings were concordant with conventional cytogenetic results with the exception of one case of triploidy. It was found in the first-tier test study that aCGH detected 20% (44/220) clinically significant copy number variants (CNV), of which 21 were common aneuploidies and 23 had other chromosomal imbalances. There were 3.2% (7/220) samples with CNVs detected by aCGH but not by conventional cytogenetics. In the ‘further-test’ study, the additional diagnostic yield of detecting chromosome imbalance was 6% (9/150). The overall detection for CNVs of unclear clinical significance was 2.7% (10/370) with 0.9% found to be de novo. Eleven loci of common CNVs were found in the local population. Conclusion Whole-genome aCGH offered a higher resolution diagnostic capacity than conventional karyotyping for prenatal diagnosis either as a first-tier test or as a ‘further-test’ for pregnancies with fetal ultrasound anomalies. We propose replacing conventional cytogenetics with aCGH for all pregnancies undergoing invasive diagnostic procedures after excluding common aneuploidies and triploidies by quantitative fluorescent PCR. Conventional cytogenetics can be reserved for visualization of clinically significant CNVs.

Under-recognition of 22q11.2 deletion in adult Chinese patients with conotruncal anomalies: implications in transitional care.

22q11.2 deletion syndrome (22q11.2DS) is a multi-systemic disorder with high phenotypic variability. Under-diagnosis in adults is common and recognition of facial dysmorphic features can be affected by age and ethnicity. This study aims to determine the prevalence of undiagnosed 22q11.2DS in adult Chinese patients with conotruncal anomalies and to delineate their facial dysmorphisms and extra-cardiac manifestations. We recruited consecutively 156 patients with conotruncal anomalies in an adult congenital heart disease (CHD) clinic in Hong Kong and screened for 22q11.2DS using fluorescence-PCR and fluorescence in-situ hybridization. Assessment for dysmorphic features was performed by a cardiologist at initial screening and then by a clinical geneticist upon result disclosure. Clinical photographs were taken and childhood photographs collected. Eighteen patients (11.5%) were diagnosed with 22q11.2DS, translating into 1 previously unrecognized diagnosis of 22q11.2DS in every 10 adult patients with conotruncal anomalies. While dysmorphic features were detected by our clinical geneticist in all patients, only two-thirds were considered dysmorphic by our cardiologist upon first assessment. Evolution of facial dysmorphic features was noted with age. Extra-cardiac manifestations included velopharyngeal incompetence or cleft palate (44%), hypocalcemia (39%), neurodevelopmental anomalies (33%), thrombocytopenia (28%), psychiatric disorders (17%), epilepsy (17%) and hearing loss (17%). We conclude that under-diagnosis of 22q11.2DS in Chinese adults with conotruncal defects is common and facial dysmorphic features may not be reliably recognized in the setting of adult CHD clinic, referral for genetic evaluation and molecular testing for 22q11.2DS should be offered to patients with conotruncal defects.

The Clinical Impact of Chromosomal Microarray on Paediatric Care in Hong Kong

Objective To evaluate the clinical impact of chromosomal microarray (CMA) on the management of paediatric patients in Hong Kong. Methods We performed NimbleGen 135k oligonucleotide array on 327 children with intellectual disability (ID)/developmental delay (DD), autism spectrum disorders (ASD), and/or multiple congenital anomalies (MCAs) in a university-affiliated paediatric unit from January 2011 to May 2013. The medical records of patients were reviewed in September 2013, focusing on the pathogenic/likely pathogenic CMA findings and their “clinical actionability” based on established criteria. Results Thirty-seven patients were reported to have pathogenic/likely pathogenic results, while 40 had findings of unknown significance. This gives a detection rate of 11% for clinically significant (pathogenic/likely pathogenic) findings. The significant findings have prompted clinical actions in 28 out of 37 patients (75.7%), while the findings with unknown significance have led to further management recommendation in only 1 patient (p<0.001). Nineteen out of the 28 management recommendations are “evidence-based” on either practice guidelines endorsed by a professional society (n = 9, Level 1) or peer-reviewed publications making medical management recommendation (n = 10, Level 2). CMA results impact medical management by precipitating referral to a specialist (n = 24); diagnostic testing (n = 25), surveillance of complications (n = 19), interventional procedure (n = 7), medication (n = 15) or lifestyle modification (n = 12). Conclusion The application of CMA in children with ID/DD, ASD, and/or MCAs in Hong Kong results in a diagnostic yield of ∼11% for pathogenic/likely pathogenic results. Importantly the yield for clinically actionable results is 8.6%. We advocate using diagnostic yield of clinically actionable results to evaluate CMA as it provides information of both clinical validity and clinical utility. Furthermore, it incorporates evidence-based medicine into the practice of genomic medicine. The same framework can be applied to other genomic testing strategies enabled by next-generation sequencing.

Genetic Counseling/Consultation in South-East Asia: A Report from the Workshop at the 10th Asia Pacific Conference on Human Genetics

This paper reports on the workshop ‘Genetic Counseling/Consultations in South-East Asia’ at the 10th Asia Pacific Conference on Human Genetics in Kuala Lumpur, Malaysia, in December 2012. The workshop brought together professionals and language/communication scholars from South-East Asia, and the UK. The workshop aimed at addressing culture- and context-specific genetic counseling/consultation practices in South-East Asia. As a way of contextualizing genetic counseling/consultation in South-East Asia, we first offer an overview of communication-oriented research generally, drawing attention to consultation and counseling as part of a communicative continuum with distinctive interactional features. We then provide examples of genetic counseling/consultation research in Hong Kong. As other countries in South-East Asia have not yet embarked on communication-oriented empirical research, we report on the current practices of genetic counseling/consultation in these countries in order to identify similarities and differences as well as key obstacles that could be addressed through future research. Three issues emerged as ‘problematic’: language, religion and culture. We suggest that communication-oriented research can provide a starting point for evidence-based reflections on how to incorporate a counseling mentality in genetic consultation. To conclude, we discuss the need for creating a platform for targeted training of genetic counselors based on communication-oriented research findings.

A prenatal case of split-hand malformation associated with 17p13.3 triplication - a dilemma in genetic counseling.

Copy number gain of 17p13.3 has been shown to be associated with developmental delay/autism and Split-Hand-Foot malformation. We report a case of fetus with bilateral split-hand malformation detected on prenatal ultrasound. Array comparative genomic hybridization detected 2 maternally inherited copy number gains in the 17p13.3 region with one of them involving the BHLHA9 gene and part of the YWHAE gene. The mother is normal in intelligence with mild right foot anomaly only. Although the BHLHA9 copy gain is known to be associated with split-hand-foot malformation, the penetrance and expressivity is highly variable. More challenging is the effect of partial YWHAE copy number gain on neurodevelopment is inconclusive based on current literature. This case highlights the difficulties of prenatal genetic counseling in array comparative genomic hybridization findings in clinical situation with incomplete understanding of genotype-phenotype correlation.

Pregnancy-associated plasma protein A (PAPP-A) to predict adverse fetal outcomes in Chinese: What is the optimal cutoff value?

abstract A low level of PAPP-A predicts adverse fetal outcomes. As Chinese pregnant women have a higher level of PAPP-A, the predictive performance of PAPP-A and its optimal cutoff value might be different. This study aims to establish a PAPP-A cutoff value in the Chinese population that identifies adverse fetal outcomes. We retrospectively analysed 4936 spontaneous singleton pregnancies of Chinese women who underwent first-trimester combined Down’s screening in our unit from March 2010 to January 2014 and had delivery information available. A composite adverse fetal outcome encompassed intrauterine fetal loss (including miscarriages and stillbirths), and live births either before 32 weeks or weighing less than −2 standard deviation (SD) for gestation. The area under the curve of the receiver-operator characteristic curve for prediction of the composite adverse outcome using PAPP-A was 0.626 (95% CI =0.612–0.640, p < 0.0001). PAPP-A ≤ 0.23 multiples of median (MoM) identified 0.6% of Chinese pregnant women to be at significant risk of adverse fetal outcome (positive likelihood ratio 11.2, positive predictive value 21.4%) despite a low sensitivity (5.1%, 95% CI =1.9–10.8). The negative predictive value was high (97.7%). The commonly used cutoff of 0.4 MoM was associated with a positive likelihood ratio of 3.7 only. A prospective study is warranted.

A Fetus with Hb Bart’s Disease Due to Maternal Uniparental Disomy for Chromosome 16

Abstract We here report an unusual case of Hb Bart’s (γ4) disease. Thalassemia screening of a couple showed that the wife was an α0-thalassemia (α0-thal) carrier and her husband’s mean corpuscular volume (MCV) was normal. Chorionic villus sampling (CVS) was performed at 13 weeks’ gestation for positive Down syndrome screening and chromosomal study of the cultured CVS showed a normal karyotype. Ultrasound examination at 22 weeks’ gestation showed fetal cardiomegaly and raised middle cerebral artery peak systolic velocity. Cordocentesis confirmed fetal anemia and showed Hb Bart’s disease. Multiplex gap-polymerase chain reaction (gap-PCR) for α-thal deletions on DNA extracted from the CVS showed the presence of a homozygous α0-thal − −SEA (Southeast Asian) deletion. The husband was found to be a carrier of the α+-thal −α3.7 (rightward) deletion. Non paternity was excluded by fluorescent PCR using short tandem repeat (STR) markers on chromosomes 13, 18 and 21. A de novo terminal deletion of chromosome 16 was excluded by array comparative genomic hybridization (aCGH). Detection of uniparental disomy (UPD), using STR markers on chromosome 16 showed maternal uniparental isodisomy from 16pter to 16p13.2, and uniparental heterodisomy from 16p13.13 to 16qter.

Pregnancy-associated plasma protein A for prediction of fetal growth restriction.

Low levels of pregnancy-associated plasma protein A (PAPP-A) are correlatedwith birthweights of below the 10th percentile [1]. However, it is unknown whether levels of PAPP-A can be used to predict severe fetal growth restriction, which would be more clinically relevant. To address this issue, a retrospective analysis of singleton live births amongChinesewomen after natural conceptionwas performed. Included patients had undergone combined Down syndrome screening in Queen Mary Hospital or Tsan Yuk Hospital, Hong Kong, between March 1, 2010, and January 31, 2014. The test was performed between the start of the 11thweek of pregnancy and the end of the 13thweek. Pregnancies affected by chromosomal or structural abnormalities were excluded. Because the analysis was a review of information extracted from existing clinical database without involvement of patients or any intervention, institutional review board approval and informed consent was not needed. The screening consisted of ultrasonography and a blood test. Ultrasonography was used to measure the fetal crown–rump length and nuchal translucency according to the guidelines of the Fetal Medicine Foundation [2]. The maternal serum levels of PAPP-A and free β-human chorionic gonadotropin were measured by Delfia Xpress (PerkinElmer, Waltham, MA, USA) and converted to a multiple of the median adjusted for maternal weight for the local Chinese population. Birth weight was adjusted for fetal sex using a gestation-specific normogram for the study population [3]. Receiver operating characteristic curves were derived with MedCalc version 13.1.2 (MedCalc Software, Ostend, Belgium) to determine the performance of PAPP-A in the prediction of different degrees of growth restriction (birth weight b10th percentile and b2 standard deviations [SDs] below the mean value for gestational age). P b 0.05 was considered statistically significant. Among 4918 singleton live births included, 378 (7.7%) newborns weighed below the 10th percentile and 77 (1.6%) weighed less than two SDs below the mean value for their gestational age. The area under the receiver operating characteristic curve for prediction of birth weight less than two SDs below the mean value using PAPP-A was 0.653 (95% confidence interval [CI] 0.639–0.666) and that for birth weight below the 10th percentile was 0.595 (95% CI 0.581–0.608). Both areas were significantly above 0.5 (Pb 0.001). The performance of PAPP-Awasbetter for prediction of birthweight less than two SDs below themean than for prediction of birth weight below the 10th percentile because the area under the curve was larger and the 95% CIs do not overlap. Among the 4918 mothers, 37 (0.8%) smoked during pregnancy. Smoking status and free β-human chorionic gonadotropin level were not correlated with low birth weight by either definition used in the present analysis (data not shown). Overall, the present analysis has shown that measurements of maternal serum PAPP-A concentration in the first trimester predict severe fetal growth restriction (birthweight less than two SDs below themean value for gestational age) more effectively than they predict a birth weight below the 10th percentile among a Chinese population.

Expanded Prader–Willi syndrome due to chromosome 15q11.2–14 deletion: Report and a review of literature†

We report on a male infant with de novo unbalanced t(5;15) translocation resulting in a 17.23 Mb deletion within 15q11.2–q14 and a 25.12 kb deletion in 5pter. The 15q11.2–q14 deletion encompassed the 15q11.2–q13 Prader–Willi syndrome (PWS) critical region and the recently described 15q13.3 microdeletion syndrome region while the 5pter deletion contained no RefSeq genes. From our literature review, patients with similar deletions in chromosome 15q exhibit expanded phenotype of severe developmental delay, protracted feeding problem, absent speech, central visual impairment, congenital malformations and epilepsy in addition to those typical of PWS. The patient reported herein had previously unreported anomalies of mega cisterna magna, horseshoe kidney and the rare neonatal interstitial lung disease known as pulmonary interstitial glycogenosis. Precise breakpoint delineation by microarray is useful in patients with atypical PWS deletions to guide investigation and prognostication.

Informed choice and decision making in women offered cell-free DNA prenatal genetic screening.

Department of Obstetrics and Gynecology, Princess Margaret Hospital, Hong Kong Prenatal Diagnostic Laboratory, Tsan Yuk Hospital and Department of Obstetrics and Gynecology, Queen Mary Hospital, Hong Kong Department of Obstetrics and Gynecology, Tuen Mun Hospital, Hong Kong Department of Obstetrics and Gynecology, United Christian Hospital, Hong Kong Department of Obstetrics and Gynecology, Queen Elizabeth Hospital, Hong Kong Department of Obstetrics and Gynecology, Pamela Youde Nethersole Easten Hospital, Hong Kong *Correspondence to: Tsz-Kin Lo. E-mail: lo_tsz_kin@yahoo.com.hk