DNA methylation-based sex classifier to predict sex and identify sex chromosome aneuploidy

Background Sex is an important covariate of epigenome-wide association studies due to its strong influence on DNA methylation patterns across numerous genomic positions. Nevertheless, many samples on the Gene Expression Omnibus (GEO) frequently lack a sex annotation or are incorrectly labelled. Considering the influence that sex imposes on DNA methylation patterns, it is necessary to ensure that methods for filtering poor samples and checking of sex assignment are accurate and widely applicable. Results Here we presented a novel method to predict sex using only DNA methylation beta values, which can be readily applied to almost all DNA methylation datasets of different formats (raw IDATs or text files with only signal intensities) uploaded to GEO. We identified 4345 significantly (p<0.01) sex-associated CpG sites present on both 450K and EPIC arrays, and constructed a sex classifier based on the two first principal components of the DNA methylation data of sex-associated probes mapped on sex chromosomes. The proposed method is constructed using whole blood samples and exhibits good performance across a wide range of tissues. We further demonstrated that our method can be used to identify samples with sex chromosome aneuploidy, this function is validated by five Turner syndrome cases and one Klinefelter syndrome case. Conclusions This proposed sex classifier not only can be used for sex predictions but also applied to identify samples with sex chromosome aneuploidy, and it is freely and easily accessible by calling the ‘estimateSex’ function from the newest wateRmelon Bioconductor package (https://github.com/schalkwyk/wateRmelon).

Noninvasive prenatal testing for assessing foetal sex chromosome aneuploidy: a retrospective study of 45,773 cases

Objective To assess the positive predictive value (PPV) of noninvasive prenatal testing (NIPT) as a screening test for sex chromosome aneuploidy (SCA) with different maternal characteristics and prenatal decisions in positive cases. Materials and methods We retrospectively analysed 45,773 singleton pregnancies with different characteristics that were subjected to NIPT in the Maternity and Child Health Hospital of Anhui Province. The results were validated by karyotyping. Clinical data, diagnostic results, and data on pregnancy outcomes were collected. Results In total, 314 cases were SCA positive by NIPT; among those, 143 underwent invasive prenatal diagnostic testing, and 58 were true-positive. Overall, the PPVs for 45,X, 47,XXX, 47,XXY and 47,XYY were 12.5%, 51.72%, 66.67% and 83.33%, respectively. Interestingly, when only pregnant women of advanced maternal age (AMA) were screened, the PPVs for 45,X, 47,XXX, 47,XXY and 47,XYY were 23.81%, 53.33%, 78.95%, and 66.67%, respectively. The frequency of SCA was significantly higher in the AMA group than in the non-AMA group. The frequencies of 47,XXX and 47,XXY were significantly correlated with maternal age. Conclusion NIPT performed better in predicting sex chromosome trisomies than monosomy X, and patients with 45,X positive foetuses were more eager to terminate pregnancy than those with 47,XXX and 47,XYY. AMA may be a risk factor of having a foetus with SCA. Our findings may assist in genetic counselling of AMA pregnant women. Our pre- and posttest counselling are essential for familiarizing pregnant women with the benefits and limitations of NIPT, which may ease their anxiety and enable them to make informed choices for further diagnosis and pregnancy decisions.

DNA methylation-based sex classifier to predict sex and identify sex chromosome aneuploidy

Sex is an important covariate of epigenome-wide association studies due to its strong influence on DNA methylation patterns across numerous genomic positions. Nevertheless, many samples on the Gene Expression Omnibus (GEO) frequently lack a sex annotation or are incorrectly labelled. Considering the influence that sex imposes on DNA methylation patterns, it is necessary to ensure that methods for filtering poor samples and checking of sex assignment are accurate and widely applicable. In this paper, we presented a novel method to predict sex using only DNA methylation density signals, which can be readily applied to almost all DNA methylation datasets of different formats (raw IDATs or text files with only density signals) uploaded to GEO. We identified 4345 significantly (p < 0.01) sex-associated CpG sites present on both 450K and EPIC arrays, and constructed a sex classifier based on the two first components of PCAs from the two sex chromosomes. The proposed method is constructed using whole blood samples and exhibits good performance across a wide range of tissues. We further demonstrated that our method can be used to identify samples with sex chromosome aneuploidy, this function is validated by five Turner syndrome cases and one Klinefelter syndrome case. The proposed method has been integrated into the wateRmelon Bioconductor package.

Non-invasive Prenatal Testing for Assessing Fetal Sex Chromosome Aneuploidy: A Retrospective Study of 45773 Cases

Objective: To assess the positive predictive value (PPV) of non-invasive prenatal testing (NIPT) as a screening test for sex chromosome aneuploidy (SCA) with different maternal characteristics and prenatal decision in positive cases. Materials and Methods: We retrospectively analyzed 45773 singleton pregnancies with different characteristics that were subjected to NIPT in Maternity and Child Health Hospital of Anhui Province. The results were validated by karyotyping. Clinical data, diagnostic results, and pregnancy outcomes were collected.Results: A total of 314 cases were SCA positive by NIPT; among those, 143 underwent invasive prenatal diagnostic testing, and 58 resulted as true-positive. Overall, the PPV for 45,X, 47,XXX, 47,XXY and 47,XYY was 12.5%, 51.72%, 66.67% and 83.33%, respectively. Interestingly, when screening only pregnant women in advanced maternal age (AMA), the PPV for 45,X, 47,XXX, 47,XXY and 47,XYY was 23.81%, 53.33%, 78.95%, and 66.67%, respectively. AMA was a high-risk predictor of having a fetus with SCA. The frequencies of 47, XXX, and 47,XXY were significantly correlated with maternal age.Conclusion: NIPT performed better in predicting sex chromosome trisomies than monosomy X, and patients with 45,X positive fetus were more eager to terminate pregnancy compared to those with 47,XXX and 47, XYY. Our findings may assist in genetic counseling of AMA pregnant women. Our Pre- and post-test counseling are essential for familiarizing pregnant women with the benefits and limitations of the NIPT, which may ease their anxiety and provide them with the informed choice for further diagnosis and pregnancy decision.

Clinical Experience with Fetal Sex Chromosome Aneuploidy Identified by Non-Invasive Prenatal Testing in 45773 Cases

Objective: To investigate the positive predictive value (PPV) and clinical features of non-invasive prenatal testing (NIPT) as a screening method in detecting sex chromosome aneuploidy (SCA) within a high-risk population at the Maternity and Child Health Hospital of Anhui Province.Methods: From June 2015 to June 2019, 45773 women with singleton pregnancies volunteered to take an NIPT. Cell-free fetal DNA was extracted for high-throughput sequencing and amniocentesis karyotype analysis was performed in pregnant women. Results: 314 high-risk pregnant women underwent NIPT and 143 chose invasive prenatal diagnosis. Karyotype analysis was performed in amniotic fluid cells, wherein 7 cases of 45,X (PPV: 12.50%), 16 cases of 47,XXX (PPV: 55.17%), 25 cases of 47,XXY (PPV: 71.43%), and 10 cases of 47,XYY(PPV: 76.92%) were confirmed. The PPV of NIPT for SCA was 40.56%. The rate of SCA detected in women aged 40 years and older was 0.39%, which was significantly different from that detected in women aged <30, 30–34, and 35–39 years (P < 0.05). The detection rates of 47,XXX and 47,XXY were significantly correlated with maternal age (P < 0.05), but those of 45,X and 47,XYY showed no significant correlation with maternal age.Conclusion: NIPT can be applied for the detection of SCA, but the detection accuracy is low. Genetic counseling and further prenatal diagnosis should be provided.