INTERNATIONAL STANDARDS ON FOOD AND ENVIRONMENTAL RADIOACTIVITY MEASUREMENT FOR RADIOLOGICAL PROTECTION: STATUS AND PERSPECTIVES.

Radiological protection is a matter of concern for members of the public and thus national authorities are more likely to trust the quality of radioactivity data provided by accredited laboratories using common standards. Normative approach based on international standards aims to ensure the accuracy or validity of the test result through calibrations and measurements traceable to the International System of Units. This approach guarantees that radioactivity test results on the same types of samples are comparable over time and space as well as between different testing laboratories. Today, testing laboratories involved in radioactivity measurement have a set of more than 150 international standards to help them perform their work. Most of them are published by the International Standardization Organization (ISO) and the International Electrotechnical Commission (IEC). This paper reviews the most essential ISO standards that give guidance to testing laboratories at different stages from sampling planning to the transmission of the test report to their customers, summarizes recent activities and achievements and present the perspectives on new standards under development by the ISO Working Groups dealing with radioactivity measurement in connection with radiological protection.

Application of risk score analysis to low-coverage whole genome sequencing data for the noninvasive detection of trisomy 21, trisomy 18, and trisomy 13.

OBJECTIVES: Clinical performance of a low coverage, low cost, massively parallel sequencing (MPS)-based assay to stratify risk of trisomy 21, 18, and 13 pregnancies was determined. METHODS: The study included 1100 samples with birth outcome or karyotype results, comprising low-risk patients (84.2%) negative for risk indications from maternal age, serum screening, ultrasound, or family history, and high-risk patients (15.8%) with at least one of the aforementioned indications. Cell free DNA (cfDNA) was extracted from maternal plasma. Library preparation incorporated 96 index barcodes to enable sequencing on a HiSeq 2000 or 2500. Risk scores were calculated using chromosomal representation, fetal fraction, and maternal age at the estimated date of delivery. A risk score greater than or equal to 1 in 100 was used to stratify samples as high risk for trisomy 21, trisomy 18, or trisomy 13. RESULTS: Sensitivity and specificity were calculated based on risk group stratification. Trisomy 21, trisomy 18, and trisomy 13 were detected with greater than 99% sensitivity and 99.9% specificity. Fetal sex classification accuracy was 99.3%. CONCLUSIONS: We conclude that simplified MPS can be used to stratify the risk of pregnancies for trisomy 21, trisomy 18, and trisomy 13 and accurately determine fetal sex. © 2015 John Wiley & Sons, Ltd.

Circulating cell free DNA testing: are some test failures informative?

OBJECTIVE: The proportion of circulating cell free DNA derived from the feto-placental unit (fetal fraction or FF) correlates with test success and interpretation reliability. Some fetal disorders are associated with systematically lower FF, sometimes resulting in noninformative results. METHODS: We analyzed results from pregnancies tested in a nested case/control study derived from a cohort of 4664 high-risk pregnancies. Low FF was defined before and after adjusting for maternal weight and gestational age. RESULTS: Compared with euploid pregnancies, the median FF was significantly higher in Down syndrome pregnancies (ratio 1.17) and significantly lower in trisomy 18 and triploid pregnancies (ratios 0.71 and 0.19, respectively). Among 2157 pregnancies tested, 13 (0.6%) had FF <3.0% (all noninformative), including three trisomy 18 and three triploidy fetuses. After adjustment, 16 pregnancies (0.7%) had FF <0.3 multiples of the median (six informative), including one trisomy 18 and three triploidy fetuses. Modeled positive predictive values for low and high-risk populations were 7% and 30%, respectively. CONCLUSION: Among women with noninformative results attributable to low FF, trisomy 18 and/or triploidy risk are sufficiently high to warrant offering additional assessments (e.g. ultrasound). If the testing indication is ultrasound abnormality, amniocentesis and karyotype/microarray should be considered. © 2014 John Wiley & Sons, Ltd.

ISO standards on test methods for water radioactivity monitoring.

Water is vital to humans and each of us needs at least 1.5L of safe water a day to drink. Beginning as long ago as 1958 the World Health Organization (WHO) has published guidelines to help ensure water is safe to drink. Focused from the start on monitoring radionuclides in water, and continually cooperating with WHO, the International Standardization Organization (ISO) has been publishing standards on radioactivity test methods since 1978. As reliable, comparable and 'fit for purpose' results are an essential requirement for any public health decision based on radioactivity measurements, international standards of tested and validated radionuclide test methods are an important tool for production of such measurements. This paper presents the ISO standards already published that could be used as normative references by testing laboratories in charge of radioactivity monitoring of drinking water as well as those currently under drafting and the prospect of standardized fast test methods in response to a nuclear accident.

Circulating cell-free fetal DNA for the detection of RHD status and sex using reflex fetal identifiers.

OBJECTIVE: To determine the sensitivity and specificity of circulating cell-free fetal DNA in determining the fetal RHD status and fetal sex. METHODS: Maternal blood was collected in each trimester of pregnancy from RhD negative nonalloimmunized women. Whole blood was centrifuged, separated into plasma and buffy coat, and frozen at -80°C. DNA analysis was conducted via allele-specific primer extensions for exons 4, 5, and 7 of the RHD gene and for a 37-base pair insertion in exon 4 (RHD pseudogene; psi) three Y-chromosome sequences (SRY, DBY, and TTY2), and an extraction control (TGIFL-like X/Y). RhD serotyping on cord blood and gender assessment of the newborns were entered into a Web-based database. RESULTS: One hundred twenty women were enrolled. The median gestational age at the first venipuncture was 12.4 (range: 10.6-13.9) weeks with 120 samples drawn; 118 samples were drawn at 17.6 (16-20.9) weeks; and 113 samples at 28.7 (27.9-33.9) weeks. Overall accuracy for RHD was 99.1%, 99.1%, and 98.1% for each trimester and was 99.1%, 99.1%, and 100% for fetal sex determination. CONCLUSIONS: Fetal RHD genotyping and sex can be very accurately determined in all three trimesters using circulating cell-free fetal DNA in the maternal circulation.

International standardisation work on the measurement of radon in air and water.

Radon is considered to be the main source of human exposure to natural radiation. As stated by the World Health Organization, the exposure due to the inhalation of indoor radon is much greater than the one via the ingestion of water as radon degasses from water during handling. In response to these concerns about the universal presence of radon, environmental assessment studies are regularly commissioned to assess the radon exposure of public and workers. The credibility of such studies relies on the quality and reliability of radon analysis as well as on the sample representativeness of the radiological situation. The standard-setting approach, based on consensus, seemed to lend itself to a settlement of technical aspects of potential comparison. At present, two Working Groups of the International Standardization Organization are focussing on drafting standards on radon and its decay products measurement in air and water. These standards, which aim for a set of rigorous metrology practices, will be useful for persons in charge of the initial characterisation of a site with respect to natural radioactivity as well as to those performing the routine surveillance of specific sites.

Screening for the aneuploid fetus.

Advances in ultrasound technology have dramatically improved the detection of fetal defects. Although only an invasive test can provide a diagnosis, the incorporation of sonography into current biochemically based screening programs should significantly improve the detection of a host of other physically based fetal abnormalities. This article provides an overview and discussion of the prenatal sonographic features that may suggest the presence of a significant chromosomal abnormality.

Informed consent for maternal serum alpha-fetoprotein screening in an inner city population: how informed is it?

OBJECTIVE: To determine if women who received information from a provider and viewed a videotape about maternal serum alpha-fetoprotein (MSAFP) screening understood enough to sign informed consent. DESIGN: A prospective qualitative design using tape recorded interviews of women who were provided information regarding MSAFP testing from a provider and from viewing a videotape. PARTICIPANTS: Fifty-three inner city pregnant women (58% Hispanic, 39% African-American, 3% white). RESULTS: Two women answered all questions correctly; no one answered all questions incorrectly. Sixty-two percent correctly answered "What is MSAFP?" Sixteen percent thought "something has to be taken from my belly" for the test. Fifty-nine percent understood that children with spina bifida could have difficulty walking or urinary problems. Seventy-two percent thought their infant would be healthy in all respects if the test was negative. Only 45% could describe the follow-up to a positive test. Eighty percent planned to have the test. Many misconceptions were apparent, and for some knowledge items, as many as 80% of the women answered incorrectly. CONCLUSIONS: Obtaining truly informed consent for a complex test is not a simple process. Participants met a few, but not all, of the criteria for informed consent. Women understood that the test was voluntary, but their comprehension of the meaning and implication of a positive test results was deficient. Despite this, they signed the informed consent document. The larger question of just how much comprehension is required to consider a woman "informed" has not been answered.

Noninvasive first-trimester screening for fetal aneuploidy.

We reviewed all studies concerning noninvasive first trimester screening for fetal aneuploidy obtained from a MEDLINE search through June 1996 with additional sources identified through cross-referencing. Three screening and diagnostic modalities are of potential application in noninvasive first trimester testing for fetal aneuploidy: ultrasound, maternal biochemical markers, and analysis of fetal cells retrieved from maternal sources. Sensitivities of the sonographic finding of nuchal translucency thickness in combination with maternal age for trisomy 21, performed between 10 and 14 weeks of gestation in experienced hands, and maternal biochemical markers independently may be as high as 86 percent and 60 percent, respectively. Sensitivity, specificity, and predictive values of these diagnostic modalities alone, in combination with each other, or in conjunction with other predisposing factors such as maternal age, in large low risk populations have not currently been established. Analysis of fetal cells retrieved from maternal sources, although more complex, may offer definitive noninvasive prenatal diagnosis yet is not currently available in clinical practice. We conclude that noninvasive first trimester screening for fetal aneuploidy modalities including sonographic examination for nuchal translucency thickness and maternal biochemical markers, is feasible. Clinical feasibility; and all-encompassing clinical management paradigms of these and other early noninvasive first trimester screening methods for fetal aneuploidy, are not yet available.

Levels of urinary beta-core fragment, total oestriol, and the ratio of the two in second-trimester screening for Down syndrome.

Levels of beta-core fragment and total oestriol in second-trimester maternal urine samples were measured in 32 Down syndrome pregnancies and 206 control pregnancies. Beta-core fragment and total oestriol values were corrected for the urinary creatinine level and expressed as multiples of the control medians (MOM). In addition, the ratio of the beta-core fragment level to the total oestriol level, without creatinine correction, was calculated, and expressed as MOM values. The median beta-core fragment, total oestriol, and ratio levels in Down syndrome cases were 5.42, 0.64, and 9.32 MOM, respectively. In the Down syndrome pregnancies, 66 per cent of the beta-core fragment levels were above the 95th centile of control levels, while 22 per cent of the total oestriol levels were below the fifth centile of control levels. In combination with maternal age, measurement of beta-core fragment and total oestriol levels in Down syndrome pregnancy resulted in an 80 per cent detection rate at a 5 per cent false-positive rate. Use of the ratio resulted in a univariate detection rate of 72 per cent. In combination with maternal age, the ratio resulted in a detection rate of 81 per cent at a 5 per cent false-positive rate. Based on this unmatched study, the measurement of a ratio of beta-core fragment to total oestriol levels, without the need for creatinine correction, may be useful in screening for fetal Down syndrome in second-trimester urine.

The genetics of ovarian cancer: an assessment of current screening protocols and recommendations for counseling families at risk.

Although the need for effective ovarian cancer screening is apparent, a highly sensitive and specific screening methodology has yet to be elucidated. 42-44 Given that there are more than 43 million women in the United States older than 45 years of age and that the average cost of a pelvic sonogram is $ 275 (and $ 45 for CA125 screening), the screening of this population is estimated to increase health care costs by $ 14 billion per year. 45 The additional cost of BRCA1 screening varies according to the level of diagnostic effort required to establish BRCA1 gene mutations in a particular family and ranges from $ 295 to $ 1,200 per sample. Assuming an average cost of $ 600 per sample, initial screening of these same women would likely increased costs in excess of $ 25 billion. Current knowledge and technology in ovarian cancer screening has not yet proved beneficial for the general population or for women with fewer than two affected family members. For women with two or more affected family members, there is a 3% chance of that patient being a proband in a hereditary cancer syndrome family. 11,46 In this group, who may be at increased risk for developing a malignancy, heightened surveillance is warranted, although there are still no data to confirm that screening even these high-risk women will reduce mortality. Nevertheless, annual bimanual examination, serum CA125, and transvaginal sonography are recommended among this particular subgroup of women at risk, and are likely to be recommended for young, asymptomatic, at-risk women who screen positive for the 185delAG BRCA1 deletion commonly found in persons of Ashkenazi Jewish ancestry. It is only through prospective, randomized trials that reliable data regarding the risk/benefit ratio of ovarian cancer screening among various populations at risk will be determined. The results of the prospective/randomized PLCO trial and the mature data from ongoing prospective, nonrandomized screening trials for women with a family history of cancer may provide this information and are eagerly awaited.

Prenatal diagnosis of type 2 Pfeiffer syndrome.

Pfeiffer syndrome is an autosomal dominantly inherited disorder consisting of craniosynostosis, a flattened midface with a beaked nose and ocular proptosis, and broad and medially deviated thumbs and great toes. Recently, based on clinical findings, the disorder has been divided into three subtypes: type 1, characterized by mild expression; type 2, in which clover leaf skull deformity and multiple congenital anomalies are present at birth; and type 3, which is similar to type 2, but lacks the presence of the clover leaf skull at birth. We describe a fetus in whom sonographic findings of clover leaf skull deformity, ocular hypertelorism, and varus deformity of the great toe led to the prenatal diagnosis of Pfeiffer syndrome type 2. We believe this is the second prenatal diagnosis of Pfeiffer syndrome, and the first time type 2 has been definitely identified in the second trimester of pregnancy.

Placental echolucencies: does their presence influence outcome following genetic amniocentesis?

Women undergoing genetic amniocentesis procedures were evaluated for the presence of ultrasonographic echolucencies within the placenta. Non-calcified sonolucencies < 4 to 5 cm were classified as subchorionic hematomas (SH). Of the 1,000 pregnancies evaluated, 153 (15%) pregnancies manifested SH prior to amniocentesis (study group). The indications for referral were similar in the study and control groups. There were 13 (1.3%) losses: 3 and 10 in the study and control groups, respectively, with no statistical difference in fetal losses between the groups: RR 1.52 (95% confidence interval 0.56-4.14; p = 0.32). Placental sonolucencies < 4 to 5 cm in diameter appear to be incidental ultrasound findings not associated with increased fetal loss following genetic amniocentesis. Complications following invasive prenatal diagnosis cannot be attributed to the presence of these common ultrasound findings.

Management of immune thrombocytopenia purpura at a military medical center.

OBJECTIVE: To investigate whether fetal platelets in immune thrombocytopenia purpura (ITP) may be predicted by antepartum assessment. METHODS: A prospective analysis was conducted of 28 pregnant women with ITP out of 8,056 deliveries. Of the 28 patients, 13 were evaluted by fetal scalp sampling and 11 were evaluated by percutaneous umbilical blood sampling (PUBS). RESULTS: The mean fetal and maternal platelet counts prior to delivery were 146,000 and 176,000, respectively. The mean fetal and maternal platelet counts after delivery were 245,000 and 149,000, respectively. Fetal cord platelet counts could not be predicted by maternal platelet count, the presence/absence of maternal direct/indirect anti-platelet antibodies, steroid therapy, or history of splenectomy. PUBS for fetal platelet assessment correlated well with fetal postdelivery counts. CONCLUSIONS: Patients with ITP rarely exhibit complications. No antepartum characteristic enhances reliable prediction of neonatal outcome. Method of delivery should be based on obstetric guidelines.

Triple marker (alpha-fetoprotein, unconjugated estriol, human chorionic gonadotropin) versus alpha-fetoprotein plus free-beta subunit in second-trimester maternal serum screening for fetal Down syndrome: a prospective comparison study.

OBJECTIVE: Our purpose was to compare the efficacy of triple-marker screening (alpha-fetoprotein, unconjugated estriol, human chorionic gonadotropin) with alpha-fetoprotein plus free beta-human chorionic gonadotropin. STUDY DESIGN: Free beta-human chorionic gonadotropin was concurrently assayed in 2349 maternal serum samples. Trivariate and bivariate algorithms were used to calculate the risk for fetal Down syndrome by the two protocols. Free beta-human chorionic gonadotropin from 12 cases of fetal Down syndrome previously screened with the triple marker was retrospectively assayed. RESULTS: Mean maternal age of our study was 29.8 years (range 14 to 51 years). The initial screen-positive rate with the triple marker was 8.0% compared with 12.8% for alpha-fetoprotein plus free beta-human chorionic gonadotropin. All three cases of fetal Down syndrome ascertained in our prospective study were detected by the triple marker; in contrast, one of three was detected by alpha-fetoprotein plus free beta-human chorionic gonadotropin. By adding 12 additional cases of fetal Down syndrome, 12 of 15 (80%) were screen positive with triple marker and nine of 15 (60%) were screen positive with alpha-fetoprotein plus free beta-human chorionic gonadotropin. CONCLUSION: The detection rate of fetal Down syndrome was greater by use of a triple marker screen than when using alpha-fetoprotein plus free beta-human chorionic gonadotropin. Our data do not support the claims of other studies that suggest that alpha-fetoprotein plus free beta-human chorionic gonadotropin is superior to triple markers.

Current maternal age recommendations for prenatal diagnosis: a reappraisal using the expected utility theory.

The expected utility theory suggests eliminating an age-specific criterion for recommending prenatal diagnosis to patients. We isolate the factors which patients and physicians need to consider intelligently in prenatal diagnosis, and show that the sole use of a threshold age as a screening device is inadequate. Such a threshold fails to consider adequately patients' attitudes regarding many of the possible outcomes of prenatal diagnosis; in particular, the birth of a chromosomally abnormal child and procedural-related miscarriages. It also precludes testing younger women and encourages testing in patients who do not necessarily require or desire it. All pregnant women should be informed about their prenatal diagnosis options, screening techniques, and diagnostic procedures, including their respective limitations, risks, and benefits.

Procedure-related fetal losses in transplacental versus nontransplacental genetic amniocentesis.

OBJECTIVE: We hypothesize that loss rates after amniocentesis do not differ in transplacental and nontransplacental taps performed by experienced operators. STUDY DESIGN: Subjects were 1000 women undergoing second-trimester amniocentesis: 745 were referred for maternal age; 132 for positive maternal serum alpha-fetoprotein screens, 41 indicating a risk for fetal neural tube defect, 91 indicating a risk for fetal chromosome abnormality; and 123 were referred for other reasons. All procedures were videotaped. The placenta was anterior in 518 cases; in 306 of these the needle went through the placenta. All pregnancies were prospectively evaluated through delivery. RESULTS: There were 13 losses among the 1000 procedures (1.3%). The transplacental losses occurred from 4 to 71 days after procedure, median 26.5 days; the nontransplacental losses from 12 days after procedure to term, median 25 days. The loss rate was essentially similar in the two categories: six transplacental (1.96%) and seven nontransplacental (1%) (relative risk 1.52 [95% confidence limits 0.84 to 2.75], p = 0.23). If the three patients with elevated maternal serum alpha-fetoprotein values were excluded from data analysis, the loss rates in the two groups were virtually identical (relative risk 0.98 [95% confidence limits 0.38 to 2.54], p = 1.0000). CONCLUSION: Transplacental amniocentesis does not appear to increase the fetal loss rate in the hands of experienced surgeons. Moreover, in view of the time span between amniocentesis and loss in both groups, a procedural cause seems questionable.

Molecular analysis of genetic diseases: an overview for clinicians.

The identification of fetal genetic disease has, for the most part, relied on examination of an end product, such as analysis of factor VIII levels obtained from cord blood in fetuses at risk for hemophilia. Advances in molecular genetics have shifted our focus in prenatal diagnosis away from protein product analysis toward etiology, making new discoveries gleaned from the Human Genome Project relevant to clinicians. This review discusses the basic principles involved in gene-based diagnosis, highlighting the complexities of current approaches to molecular diagnosis of fetal genetic disease. Given an understanding of both the theory and practice of genetic analysis, the review covers the fundamental principles of molecular biology (structure, function, packaging, and regulation) and discusses recombinant DNA techniques presently used for the analysis of mutations. Clinical examples are presented to introduce the techniques most commonly employed in service laboratories: direct detection assays, where the specific mutation is recognized, and indirect detection assays, useful for the deduction of an inheritance pattern where the actual mutation or its gene is not known but may be closely linked to known DNA polymorphisms.