Identification of fetal gender in maternal blood is a helpful tool in the prenatal diagnosis of haemophilia

Sudden unexpected postnatal collapse and BUB1B mutation: first forensic case report

Sudden unexpected postnatal collapse (SUPC) is a sudden collapse of the clinical conditions of a full-term or near-term newborn, within the first 7 days of life, that requires resuscitation with positive ventilation and who either dies, has hypoxic-ischemic encephalopathy, or requires intensive care. The incidence of SUPC is very low, and most often presents a negative prognosis. The BUB1B gene is a mitotic checkpoint of serine/threonine kinase B that encodes a protein crucial for maintaining the correct number of chromosomes during cell division. Mutations in the BUB1B gene are linked to mosaic variegated aneuploidy syndrome 1 (MVA1), a rare autosomal recessive disorder characterized by diffuse mosaic aneuploidies involving several chromosomes and tissues. This paper discusses a case of a newborn who had a spontaneous delivery. After 2 h and 10 min, the infant showed generalized hypotonia and cyanosis, and his doctors performed orotracheal intubation, cardiac massage, pharmacological hemodynamic therapy, mechanical ventilation, antibiotic therapy, and hypothermic treatment. The newborn was discharged after 5 months with the diagnosis of hypoxic-ischemic encephalopathy. Suspecting an SUPC, a complete genetic analysis was performed demonstrating a compound heterozygous mutations in the BUB1B gene. The newborn died at 6 months of life, 1 month after discharge. A complete autopsy was performed, determining that the cause of death was due to sepsis starting from a brocopneumonic process, with outcomes of hypoxic-ischemic encephalopathy (HIE). In this scenario, it is not possible to demonstrate the causal effect of this mutation, considering that it could play a causal or concausal role in the onset of SUPC. Further research based on multicenter studies, as well as on animal models, could be very useful to clarify the pathological effect of this mutation.

TriXY-Homogeneous genetic sexing of highly degraded forensic samples including hair shafts

Sexing of biological evidence is an important aspect in forensic investigations. A routinely used molecular-genetic approach to this endeavour is the amelogenin sex test, which is integrated in most commercially available polymerase chain reaction (PCR) kits for human identification. However, this assay is not entirely effective in respect to highly degraded DNA samples. This study presents a homogeneous PCR assay for robust sex diagnosis, especially for the analysis of severely fragmented DNA. The introduced triplex for the X and Y chromosome (TriXY) is based on real-time PCR amplification of short intergenic sequences (<50bp) on both gonosomes. Subsequent PCR product examination and molecular-genetic sex-assignment rely on high-resolution melting (HRM) curve analysis. TriXY was optimized using commercially available multi-donor human DNA preparations of either male or female origin and successfully evaluated on challenging samples, including 46 ancient DNA specimens from archaeological excavations and a total of 16 DNA samples extracted from different segments of eight hair shafts of male and female donors. Additionally, sensitivity and cross-species amplification were examined to further test the assay's utility in forensic investigations. TriXY's closed-tube format avoids post-PCR sample manipulations and, therefore, distinctly reduces the risk of PCR product carry-over contamination and sample mix-up, while reducing labour and financial expenses at the same time. The method is sensitive down to the DNA content of approximately two diploid cells and has proven highly useful on severely fragmented and low quantity ancient DNA samples. Furthermore, it even allowed for sexing of proximal hair shafts with very good results. In summary, TriXY facilitates highly sensitive, rapid, and costeffective genetic sex-determination. It outperforms existing sexing methods both in terms of sensitivity and minimum required template molecule lengths. Therefore, we feel confident that TriXY will prove to be a reliable addition to the toolbox currently used for sex-typing in forensic genetics and other fields of research.

Prenatal diagnosis of haemophilia B: the Italian experience

This article describes prenatal diagnosis (PND) of haemophilia B (HB) within the framework of Italian haemophilia centres and genetics laboratories. The study details the experience from six haemophilia genetic centres (three in the North, one in the Centre and two in the South of Italy) and summarizes the different techniques used to perform PND of HB during the last 15 years. To date, the Italian HB database includes 373 characterized unrelated patients and their genetic information has permitted the identification of 274 carriers of childbearing age. This database represents the main instrument for timely and precise PND. Sixty-six prenatal diagnoses were performed on 52 HB carriers whose average age at the time was 34 (ranging from 24 to 44 years). In 44 cases, genetic counselling for carrier status determination was performed before pregnancy, while eight were not studied prior to pregnancy. Foetal samples were obtained by chorionic villus sampling in 52 cases, by amniocentesis in 12 while two were diagnosed by analysis of free foetal DNA obtained from maternal peripheral blood. In 35 (53%) pregnancies the foetus was female. For 31 men (47%), haemophilia status was determined by analysis of previously determined informative markers or familial mutations (12 affected and 19 unaffected). There may be more than one laboratory involved in the PND diagnostic pathway (providing DNA extraction, karyotype analysis, gender determination, maternal contamination detection, molecular diagnosis and sequencing). Good communication between all the parties, coordinated by the haemophilia centre, is essential for a successful and rapid process.

Non-invasive prenatal diagnostic test accuracy for fetal sex using cell-free DNA a review and meta-analysis

Background

Cell-free fetal DNA (cffDNA) can be detected in maternal blood during pregnancy, opening the possibility of early non-invasive prenatal diagnosis for a variety of genetic conditions. Since 1997, many studies have examined the accuracy of prenatal fetal sex determination using cffDNA, particularly for pregnancies at risk of an X-linked condition. Here we report a review and meta-analysis of the published literature to evaluate the use of cffDNA for prenatal determination (diagnosis) of fetal sex. We applied a sensitive search of multiple bibliographic databases including PubMed (MEDLINE), EMBASE, the Cochrane library and Web of Science.

Results

Ninety studies, incorporating 9,965 pregnancies and 10,587 fetal sex results met our inclusion criteria. Overall mean sensitivity was 96.6% (95% credible interval 95.2% to 97.7%) and mean specificity was 98.9% (95% CI = 98.1% to 99.4%). These results vary very little with trimester or week of testing, indicating that the performance of the test is reliably high.

Conclusions

Based on this review and meta-analysis we conclude that fetal sex can be determined with a high level of accuracy by analyzing cffDNA. Using cffDNA in prenatal diagnosis to replace or complement existing invasive methods can remove or reduce the risk of miscarriage. Future work should concentrate on the economic and ethical considerations of implementing an early non-invasive test for fetal sex.

Cell-free fetal nucleic acid testing: a review of the technology and its applications

Cell-free fetal nucleic acids circulating in the blood of pregnant women afford the opportunity for early, noninvasive prenatal genetic testing. The predominance of admixed maternal genetic material in circulation demands innovative means for identification and analysis of cell-free fetal DNA and RNA. Techniques using polymerase chain reaction, mass spectrometry, and sequencing have been developed for the purposes of detecting fetal-specific sequences, such as paternally inherited or de novo mutations, or determining allelic balance or chromosome dosage. Clinical applications of these methods include fetal sex determination and blood group typing, which are currently available commercially although not offered routinely in the United States. Other uses of cell-free fetal DNA and RNA being explored are the detection of single-gene disorders, chromosomal abnormalities, and inheritance of parental polymorphisms across the whole fetal genome. The concentration of cell-free fetal DNA may also provide predictive capabilities for pregnancy-associated complications. The roles that cell-free fetal nucleic acid testing assume in the existing framework of prenatal screening and invasive diagnostic testing will depend on factors such as costs, clinical validity and utility, and perceived benefit-risk ratios for different applications. As cell-free fetal DNA and RNA testing continues to be developed and translated, significant ethical, legal, and social questions will arise that will need to be addressed by those with a stake in the use of this technology.

TARGET AUDIENCE

Obstetricians & Gynecologists and Family Physicians Learning Objectives: After participating in this activity, physicians should be better able to evaluate techniques and tools for analyzing cell-free fetal nucleic acids, assess clinical applications of prenatal testing, using cell-free fetal nucleic acids and barriers to implementation, and distinguish between relevant clinical features of cell-free fetal nucleic acid testing and existing prenatal genetic screening and diagnostic procedures.

Prenatal diagnosis for haemophilia: a nationwide survey among female carriers in the Netherlands

Carriers of haemophilia face difficult choices regarding prenatal diagnosis, but little is known about the determinants that influence their decisions. The aim of this study was to assess the incidence of prenatal diagnosis and potential determinants affecting the choice for prenatal diagnosis. A nationwide survey was performed among all women who underwent carriership testing for haemophilia in the Netherlands between 1992 and 2004. Prenatal diagnosis was assessed in 207 carriers of haemophilia A or B who had been pregnant. Prenatal diagnosis was categorized into early first trimester (Y-PCR testing or chorionic villus sampling) often intended to prevent the birth of a child with haemophilia, and into late prenatal diagnosis (amniocentesis or ultrasound assessment) aimed at obstetrical management. Of 207 carriers 112 (54%) underwent prenatal diagnosis. Forty-eight women underwent early prenatal diagnosis and 64 women underwent late prenatal diagnosis. In 26 pregnancies early prenatal diagnosis was positive for haemophilia, and in 18 of these pregnancies termination was opted for. The choice for early prenatal diagnosis was associated with a liberal view towards termination of pregnancy (relative risk (RR) 12.5; 95% confidence interval (CI) 3.1-51.2), severe haemophilia in the family (RR 20.2; CI 2.7-153.6), absence of a religion (RR 1.9; CI 1.1-3.1) and older age (RR 2.0; CI 1.0-3.9). The choice for late prenatal diagnosis was associated with birth year after 1970 (RR 2.3; CI 1.5-3.5) and a previous child with haemophilia (RR 2.2; CI 1.4-3.4). More than half of all Dutch haemophilia carriers underwent prenatal diagnosis. Several determinants were strongly associated with prenatal diagnosis.

Biomarkers in neonatology: the next generation of tests

Over the past two decades, neonatal clinicians have commonly used host response biomarkers to diagnose and assess the severity of systemic infection. Most of these biomarkers, such as acute-phase proteins or cytokines, are non-specific immunomodulating mediators of the inflammatory cascade. With advances in biochemical/genetic research, it is anticipated that future biomarkers will be 'organ and/or disease specific'. There is also the quest for discovery of 'novel' biomarkers to assist diagnosis and prognosis of neonatal diseases using powerful mass-screening techniques, e.g. the next-generation sequencing, proteomics and arrays. This article aims to introduce the concept of the next generation of biomarkers to practising neonatal clinicians, and, hopefully, to integrate basic science research into day-to-day clinical practice in the future.

Determination of foetal sex in pregnancies at risk of haemophilia: a qualitative study exploring the clinical practices and attitudes of health professionals in the United Kingdom

In pregnancies at risk of haemophilia, foetal sex determination is used to plan perinatal management and to guide the offer of invasive testing in pregnancies with a male foetus. Traditionally ultrasound from 12 weeks gestation has been used, but recently options for early foetal sex determination have increased following the introduction of non-invasive prenatal diagnosis (NIPD) using cell free foetal DNA in maternal plasma. This study was conducted to identify clinical practices and examine health professional attitudes regarding NIPD for foetal sex determination. A qualitative approach using one-to-one semi structured interviews was used to enable an in-depth exploration of current practice, introduction and use of NIPD and benefits and disadvantages of offering NIPD. Interviews were conducted with consultant haematologists (N = 7), specialist haemophilia nurses (N = 7), genetic counsellors (N = 6), consultants in clinical genetics (N = 5), specialist midwives (N = 2) and obstetricians (N = 5) from 24 services across the United Kingdom (UK). Key differences in how NIPD for foetal sexing is utilized throughout the UK were identified. Some services routinely offered NIPD to all carriers of haemophilia or to all carriers of severe haemophilia, others discussed the value of NIPD with all or primarily offered NIPD as a first step to invasive testing. This study informs our understanding of how NIPD is being utilized and provides unique insights into current practice. The identification of variation between services in how prenatal testing options are offered has implications for future policy and guidelines for prenatal care.

Noninvasive fetal sex determination using cell-free fetal DNA: a systematic review and meta-analysis

CONTEXT

Noninvasive prenatal determination of fetal sex using cell-free fetal DNA provides an alternative to invasive techniques for some heritable disorders. In some countries this testing has transitioned to clinical care, despite the absence of a formal assessment of performance.

OBJECTIVE

To document overall test performance of noninvasive fetal sex determination using cell-free fetal DNA and to identify variables that affect performance.

DATA SOURCES

Systematic review and meta-analysis with search of PubMed (January 1, 1997-April 17, 2011) to identify English-language human studies reporting primary data. References from review articles were also searched.

STUDY SELECTION AND DATA EXTRACTION

Abstracts were read independently to identify studies reporting primary data suitable for analysis. Covariates included publication year, sample type, DNA amplification methodology, Y chromosome sequence, and gestational age. Data were independently extracted by 2 reviewers.

RESULTS

From 57 selected studies, 80 data sets (representing 3524 male-bearing pregnancies and 3017 female-bearing pregnancies) were analyzed. Overall performance of the test to detect Y chromosome sequences had the following characteristics: sensitivity, 95.4% (95% confidence interval [CI], 94.7%-96.1%) and specificity, 98.6% (95% CI, 98.1%-99.0%); diagnostic odds ratio (OR), 885; positive predictive value, 98.8%; negative predictive value, 94.8%; area under curve (AUC), 0.993 (95% CI, 0.989-0.995), with significant interstudy heterogeneity. DNA methodology and gestational age had the largest effects on test performance. Methodology test characteristics were AUC, 0.988 (95% CI, 0.979-0.993) for polymerase chain reaction (PCR) and AUC, 0.996 (95% CI, 0.993-0.998) for real-time quantitative PCR (RTQ-PCR) (P = .02). Gestational age test characteristics were AUC, 0.989 (95% CI, 0.965-0.998) (<7 weeks); AUC, 0.994 (95% CI, 0.987-0.997) (7-12 weeks); AUC, 0.992 (95% CI, 0.983-0.996) (13-20 weeks); and AUC, 0.998 (95% CI, 0.990-0.999) (>20 weeks) (P = .02 for comparison of diagnostic ORs across age ranges). RTQ-PCR (sensitivity, 96.0%; specificity, 99.0%) outperformed conventional PCR (sensitivity, 94.0%; specificity, 97.3%). Testing after 20 weeks (sensitivity, 99.0%; specificity, 99.6%) outperformed testing prior to 7 weeks (sensitivity, 74.5%; specificity, 99.1%), testing at 7 through 12 weeks (sensitivity, 94.8%; specificity, 98.9%), and 13 through 20 weeks (sensitivity, 95.5%; specificity, 99.1%).

CONCLUSIONS

Despite interstudy variability, performance was high using maternal blood. Sensitivity and specificity for detection of Y chromosome sequences was greatest using RTQ-PCR after 20 weeks' gestation. Tests using urine and tests performed before 7 weeks' gestation were unreliable.

Factor deficiencies in pregnancy

Pregnancy, childbirth, and the puerperium are hemostatically challenging to women with bleeding disorders. This article provides general recommendations for the management of pregnant women with inherited coagulation disorders. Each factor deficiency is discussed, providing an up-to-date review of the literature and, where possible, guidance about how to manage patients throughout pregnancy, delivery, and the puerperium. The factor deficiencies covered are inherited abnormalities of fibrinogen; deficiencies of prothrombin, factor (F)V, FVII, FX, FXI, FXIII; combined deficiencies of FV and FVIII; and the inherited deficiency of vitamin K-dependent clotting factors. The management of carriers of hemophilia A and B is also discussed.

"GenderPlex" a PCR multiplex for reliable gender determination of degraded human DNA samples and complex gender constellations

The amelogenin test integrated in most commercial polymerase chain reaction (PCR) multiplex kits is routinely used in the forensic field for gender determination of DNA samples. It has been demonstrated that this test is not entirely reliable. Males with deletions in the homologous amelogenin part on the Y chromosome (AMELY) were erroneously typed as females due to lack of Y-specific amelogenin amplification. Also, primer binding site mutations that result in a failure to amplify the AMELY or the X-chromosomal part (AMELX) have been observed. For clarification of such phenomena, a new PCR multiplex (GenderPlex) is presented, co-amplifying two different regions of the amelogenin gene (55/58 and 106/112 bp for the AMELX and AMELY alleles, respectively), a 93-bp sequence stretch of the SRY gene and four mini-X-STR loci DXS7424, DXS8378, DXS6803 and GATA172D05 (maximum product size less than 140 bp). This strategy helps with the evaluation of samples for the presence of amelogenin-based primer site mutations and confirms a male genotype by the absence of heterozygote X-STR alleles and the presence of an SRY-related peak. The short amplicon sizes of all involved loci proved to be beneficial in a study on artificially degraded DNA. Furthermore, we demonstrate by means of sensitivity, human specificity and mixture studies that the multiplex is suitable for investigations in the forensic scene. Finally, the performance of the GenderPlex was evaluated on a west Eurasian population sample from Austria comprising 166 male and 104 female individuals.

Foetal sex determination in maternal blood from the seventh week of gestation and its role in diagnosing haemophilia in the foetuses of female carriers

The existence of foetal DNA in maternal blood, discovered in 1997, opened new possibilities for noninvasive prenatal diagnosis. This includes foetal sex assessment by the detection of specific Y chromosome sequences in maternal blood, particularly important when a foetus may be affected by an X-linked disorder such as haemophilia. This study aims to validate this sex assessment method and to test its clinical utility in the diagnosis of 15 potentially affected pregnancies in female carriers of haemophilia. In the validation study, 316 maternal blood samples from 196 pregnant women at gestations ranging from 5 weeks to 12 weeks were analysed. In the clinical study, 15 pregnancies at risk of having a haemophilic foetus were tested. All pregnancies in the validation study were correctly diagnosed. The accuracy and specificity of the methodology from the seventh week of gestation was 100%. The sex of all 15 pregnancies identified as being at risk of bearing a haemophilic foetus was correctly diagnosed. Foetal sex assessment by detecting specific Y chromosome sequences in maternal blood is now routinely used in our hospital because of its high accuracy from the seventh week of gestation. Reliable foetal gender determination from maternal blood of pregnant women carriers of haemophilia in the first trimester of gestation can avoid more conventional, invasive methods of prenatal diagnosis.

Circulating nucleic acids in plasma/serum

Since the discovery of circulating nucleic acids in plasma in 1948, many diagnostic applications have emerged. For example, diagnostic and prognostic potentials of circulating tumour-derived DNA have been demonstrated for many types of cancer. The parallel development of fetal-derived DNA detection in maternal plasma has opened up the possibility of non-invasive prenatal diagnosis and monitoring of many pregnancy-associated disorders. In this regard, non-invasive fetal rhesus blood group genotyping has already been translated to clinical practice. Other applications of circulating DNA in traumatology and transplant monitoring have also been reported. The more recent discoveries of circulating tumour-derived RNA and fetal-derived RNA have proven to be equally important as their DNA counterparts. Successful prenatal diagnosis of Down's syndrome by fetal RNA analysis has recently been reported. However, the definite origin and release mechanisms of circulating nucleic acids have remained incompletely understood, with cell death being suggested to be associated with such nucleic acid release. Pre-analytical standardisation will become increasingly relevant when comparing data from different laboratories. In conclusion, studies of circulating nucleic acids have promised exciting developments in molecular diagnostics in the years to come.

Haemophilia A: molecular insights

Haemophilia A is the most common inherited bleeding disorder caused by defects in the

Clin Chem Lab Med 2007;45:450–61.