Identifying the DNA methylation differences in cell-free fetal DNA: an approach towards non-invasive prenatal diagnosis of trisomy 21 in Malaysia

• Main Authors: Zainuddin, Norafiza, Roslani, Annaliza, Ismail, Rozihan, Muhammad, Siti Aeshah @ Naznin, Kaderi, Mohd Arifin, Abdul Ghafar, Nurul Fatehah
• Format: Monograph
• Language: English
• Published: 2019
• Subjects: QH426 Genetics; RG Gynecology and obstetrics
• Online Access: http://irep.iium.edu.my/75738/1/NZ_Full%20Report_FRGS15-187-0428.pdf; http://irep.iium.edu.my/75738/

The incidence of Down syndrome increases with maternal age, and its occurrence varies in different population (1 in 319 to 1 in 1000 live births). Currently, the use of cell-free fetal DNA (cffDNA) from maternal plasma was wide implemented as one of alternatives for non-invasive prenatal screening test at certain healthcare facilities. This study aims to identify the DNA methylation differences in cffDNA for trisomy 21 detection using a previously developed prediction model based on differentially methylated regions. cffDNA was isolated from 16 pregnant women, including 10 from normal pregnancies, five possible high-risk pregnancies and a confirmed trisomy 21 pregnancy. Each cffDNA extracts were fragmented, immunoprecipitated and quantified by real-time qPCR using three pairs of specific primers for chromosome 21. The calculation of D-value with the cut-off point of zero will determine the status of samples by applying the formula D = -6.331 + 0.959XEP4 +1.188XEP5 +0.424XEP6 +0.621XEP7 +0.028XEP8 + 0.387XEP10– 0.683XEP11 +0.897XEP12, where XEPi = fraction value for each marker. Cases that give a D-value above the cutting point are classified as “trisomy 21” while those with values below the cutting point are classified as “normal”. Interestingly, all our cases were classified as normal, including the confirmed trisomy case. However, this could be due to small number of cases which prevents a better discrimination between the two groups. Hence, a larger number of cases were necessary to obtain statistically validated results. Apart from intervention research, this study aims to assess the knowledge and attitudes of pregnant women on cffDNA-based prenatal diagnosis of trisomy 21 in Kuantan, Pahang. A total of 189 respondents aged 18-45 years old (30.34 ± 0.38) participated. The mean pregnancy weeks was 29.61 ± 9.11. Approximately 53% of the respondents were able to answer correctly more than half of the questions (> 5 of 9) regarding the knowledge of Down Syndrome (mean score 5.6 ± 1.8). As for the knowledge on the prenatal screening, about 48% could answer correctly more than half of the questions (≥6 of 12) with a mean score of 5.5± 3.2. The level of knowledge of Down syndrome was found to be significantly associated with maternal education level (p<0.001) while maternal age was significantly associated with the level of knowledge of Down syndrome prenatal screening (p=0.004). Our results showed our respondents did not have adequate level of knowledge on Down syndrome and its prenatal screening tests. Hence, it is suggested that intervention