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Genetic testing in the workplace: a view from the USA.

Progress in human genetics, accelerated by the Human Genome Project, is leading to a rapid proliferation in the number of genetic tests. Although they have their benefits, genetic tests have in the past been used by various societal institutions, including employers, to discriminate against and stigmatize individuals. In the light of the increase in the number of tests and some current reports of discrimination in employment, a variety of legal and regulatory measures have been proposed to prevent genetic discrimination in the workplace.

Genetic Diseases, Inborn↗

Isolation of YAC clones from the pericentromeric region of chromosome 10 and development of new genetic markers linked to the multiple endocrine neoplasia type 2A gene.

Genetic linkage mapping and contig assembly using yeast artificial chromosome (YAC) technology form the basis of our strategy to clone and define the genomic structure of the pericentromeric region of chromosome 10 containing the multiple endocrine neoplasia type 2A gene. Thus far YAC walks have been initiated from five chromosome 10 pericentromeric loci including RBP3, D10S94, RET, D10Z1, and FNRB. Long range pulsed-field gel electrophoresis maps are constructed from the YACs isolated to define clone overlaps and to identify putative CpG islands. Bidirectional YAC walks are continued by rescreening the YAC library with sequence-tagged site assays developed from end-clones. Several new restriction fragment length polymorphisms and simple sequence repeat polymorphism markers have been identified from the YAC clones. In particular, two highly informative (CA)n dinucleotide repeat markers, sTCL-1 from proximal chromosome 10p (16 alleles, PIC = 0.68) and sJRH-1 from the RBP3 locus (18 alleles, PIC = 0.88), provide useful reagents for a polymerase chain reaction-based predictive genetic test that can be performed rapidly from small amounts of DNA.

Chromosomes, Fungal↗

Genetic predisposition to breast cancer: a surgical perspective.

BACKGROUND: Molecular alterations in proto-oncogenes, tumour suppressor genes, and genes that function in DNA damage recognition and repair are considered to be hallmarks of a carcinogenic process, including breast carcinogenesis. METHODS: A computer-assisted search of the English literature (Medline database, 1990-1999) was performed, followed by a manual search of the reference list of pertinent articles retrieved. RESULTS: Hereditary breast cancer accounts for 5-10 per cent of all breast cancer cases. About 90 per cent of hereditary breast cancers involve mutation of the BRCA1 and/or BRCA2 genes. Other cancer-related genes (including myc, c-erbB2, Tsg101 and Mdgi) are involved in breast carcinogenesis, but they do not give rise to familial breast cancer syndromes. Risk estimation is the most important clinical implication. Management options for the high-risk mutation carriers include cancer surveillance and preventive strategies (prophylactic surgery or chemoprevention). CONCLUSION: Despite inadequate knowledge about the genetic predisposition to breast cancer and its clinical implications, the demand for genetic testing is likely to expand rapidly. In addition to risk estimation, cancer surveillance and preventive strategies, gene therapy offers a new and theoretically attractive approach to breast cancer management.

BRCA2 Protein↗

Recent advances in the molecular diagnosis of tuberculosis.

To date, the diagnosis of tuberculosis has not improved significantly and still relies heavily on staining and culture of sputum or other clinical specimens which were developed more than 100 years ago. Staining does not differentiate tuberculosis from other mycobacterial infections, and culture requires at least 4 to 8 weeks. These are the major problems faced by tuberculosis control programs. In response to this demand, new rapid diagnostic methods are urgently sought. In recent years, much hope has been laid on the development of molecular techniques in the routine tuberculosis laboratory. This review concentrates on 4 techniques that are increasingly used in clinical laboratories: polymerase chain reaction to detect mycobacterial DNA in clinical specimens, nucleic acid probes to identify culture, restriction fragment length polymorphism analysis to compare strains for epidemiologic purposes, and genetic-base susceptibility testing methods for rapid detection of drug resistance. Finally, the increase in the use of clinically-useful molecular biological techniques that affect turnaround time, length of stay, and patient outcome, and reduce overall hospitalization costs will continue until universal standardization for molecular diagnostic procedures are provided. At present, conventional methods should not be replaced by novel methods until the latter are shown to be of equal or greater sensitivity, specificity, reliability, and user-friendliness. However, it is expected that the newly developed molecular techniques will complement our armamentarium of diagnostic tools in the detection of tuberculosis. It is also expected that clinical protocols based on molecular methods will increase the chances for cure by selecting the most appropriate treatment and improving the quality of life of tuberculosis patients.

Drug Resistance, Microbial↗

Molecular genetic predictive testing for Alzheimer's disease: deliberations and preliminary recommendations.

Forty-one participants representing diverse professional back-grounds attended a workshop on genetic predictive testing for familial Alzheimer's disease (FAD) on January 23, 1993 at Surrey Place Centre in Toronto, Canada. Rapidly emerging molecular genetic findings in AD indicate that predictive testing is now technologically feasible for selected individuals, although defining eligibility criteria remains problematic. Legal, ethical, biomedical, and psychosocial issues related to establishing predictive testing programs for AD were discussed at the workshop. This article reflects these discussions, provides the current biomedical background for them and examines the Huntington's disease (HD) predictive testing experience. Observations concerning molecular genetic predictive testing for AD in light of its genetic heterogeneity and clinical characteristics, such as usual later age of onset than HD, are presented. It is proposed that predictive testing for AD can now be cautiously offered in a research setting primarily according to the recommendations contained within the Ethical Issues Policy Statement on Huntington's Disease Molecular Genetics Predictive Test. However, in their application to AD, some points in the statement are considered to require emphasis, modification, or currently to be of uncertain applicability. This represents an initial step in an on-going process of debate concerning AD that will be required as new advances occur in genetic and clinical research and in bioethics.

Aged↗

Attitudes of African American premedical students toward genetic testing and screening.

PURPOSE: Genetic research is progressing at a rapid rate. While most view genetic advances favorably, concerns regarding eugenics and discrimination based on genetic test results have been raised. These concerns have been found among all groups studied; however, they have particular relevance for members of the African American community. Studies have shown that because of a long history of negative experiences, African Americans have a general mistrust of the medical establishment. It is unclear whether these negative attitudes encompass genetic advances. Because there is little empiric data in the literature, it is not known whether African Americans have a positive view of genetic advances or whether they have the same level of mistrust as is seen in their attitudes toward other forms of biomedical research. METHODS: This study was conducted as an initial effort to examine the attitudes of African Americans toward recent genetic advances and, specifically, genetic testing. A cohort of 97 college-age minority students, including 78 African Americans, participating in the Health Career Enhancement for Minorities Program (HCEM) at Case Western Reserve University were surveyed. Surveys were made available before and after the summer long course, which included five lectures on basic genetic principles and medical genetics. RESULTS: Both African American students and other minority students initially (questionnaire prior to HCEM course) had an overall positive view of genetic testing. The vast majority supported genetic testing for preventive care (95%) and presymptomatic detection of disease (88%) and agreed that it should be easily available (83%). However, several concerns were expressed as well, including fears about discrimination (68%), privacy (68%), that abortions will become more common (51%), and eugenics (37%). It is interesting that in the postcourse questionnaire, the percentages of positive views remained similar to those of the precourse survey, but the number of respondents expressing concerns increased. DISCUSSION: These results suggest that the minority students surveyed view many aspects of genetic testing and other advances favorably. However, these students expressed concerns about discrimination, privacy, and eugenics. These concerns were increased, not lessened, by exposure to genetics education. One possible explanation for this observation is that the students had a greater understanding of the issues regarding genetic testing after the HCEM lectures and discussion. Of note, there was a greater negative response toward genetic screening programs among the African American students compared with the non-African American minority students. This suggests that the negative attitudes of African Americans toward biomedical research do extend to some aspects of genetics and that educational programs must be designed and implemented if this community is going to receive the maximum benefits of this advancing technology.

Adult↗

Genetic markers for retinitis pigmentosa.

OBJECTIVE: To review recent advances in the molecular genetics of retinitis pigmentosa with emphasis on the development of genetic markers that aids diagnosis and prognosis. DATA SOURCES AND EXTRACTION: Literature search of MEDLINE from 1988 to 2005 using the following key words: 'retinitis pigmentosa', 'rhodopsin', 'RP1', 'RPGR', and 'genetic counseling'. References of two genes--RHO and RP1--causing retinitis pigmentosa in the Chinese population were reviewed. STUDY SELECTION: Literature and data related to genetic markers for retinitis pigmentosa. DATA SYNTHESIS: The genetics of retinitis pigmentosa is complex. It can be sporadic or familial, with heterogeneous transmission modes. Retinitis pigmentosa is associated with nearly 40 chromosomal loci, where 32 candidate genes have been identified. A large number of mutations are known to cause retinitis pigmentosa. But no single mutation alone accounts for more than 10% of unrelated retinitis pigmentosa patients. Genetic tests for retinitis pigmentosa require screening for a consort of mutations in a large number of genes. High throughput screening technology such as denaturing high performance liquid chromatography and automated DNA sequencing should make such tests feasible. CONCLUSIONS: Rapid developments in the understanding of the genetics of retinitis pigmentosa have helped to establish genetic tests of clinical value. The complex mode of inheritance nonetheless makes genetic counselling difficult, even in the presence of positive genetic screening results.

Chromosome Mapping↗

Development of an improved species specific PCR test for detection of Haemophilus parasuis.

A PCR test for identification of Haemophilus parasuis was optimized using the 16S rDNA sequences of the 15 serotype reference strains of H. parasuis. The test was evaluated on a collection of 218 Danish field isolates as well as on 81 representatives of 27 other species, including genetically affiliated species within Pasteurellaceae. In addition, DNA preparations from 56 H. parasuis isolates from North America were included. To obtain a test that was specific for H. parasuis, a multiplex PCR using 3 different primers was developed. The PCR test produced an amplicon of approximately 1090 bp only with representatives of H. parasuis. The test was further evaluated on 55 clinical samples from 16 Danish pigs suspected for being infected with H. parasuis, showing polyserositis or septicemia at autopsy as well as on 492 nasal swabs. The test was compared with the performance of a PCR test earlier published by Oliveira et al. [Oliveira, S., Galina, L., Pijoan, C., 2001. Development of a PCR test to diagnose Haemophilus parasuis infections. J. Vet. Diagn. Invest. 13, 495-501]. The sensitivity of the present PCR test was found to be slightly lower when applied on clinical samples from diseased pigs and 10-fold lower when tested on pure cultures of H. parasuis (5CFU and 0.5CFU/PCR reaction, respectively). Addition of 1.4 x 10(5) Escherichia coli to each PCR tube did not alter the sensitivity of the tests. No difference in sensitivity of the tests was observed when tested on purified DNA. On the other hand, the present PCR test was found to be 100% species specific for H. parasuis, in contrast to the PCR test of Oliveira et al., which also tested positive for strains belonging to A. indolicus, A. porcinus, and A. minor, species commonly occurring in the upper respiratory tract. However, when the PCR test of Oliveira et al. is used on samples from systemic locations the chances for false positive results are apparently low. The present PCR test represents a rapid and reliable method for genetically based identification of H. parasuis. The high species specificity of the test makes it suitable for detection of H. parasuis in clinical samples, regardless of the presence of affiliated species and contaminating flora. As the two PCR tests differ in sensitivity and specificity, the use of both PCR tests for different purposes is a possibility.

Animals↗

Genetic testing of glycogen storage disease type Ib in Japan: five novel G6PT1 mutations and a rapid detection method for a prevalent mutation W118R.

We devised a simple method using a TaqMan fluorogenic probe for detection of a prevalent G6PT1 mutation W118R among Japanese patients with glycogen storage disease type Ib. The W118R mutation was detected in three of six newly diagnosed Japanese patients. The W118R-negative alleles were screened for causative mutations by sequencing analysis, revealing five novel mutations. The genetic tests using the simple TaqMan method coupled with sequencing analysis would facilitate the early diagnosis of this disorder.

Adult↗

Analysis of 31 CFTR mutations by polymerase chain reaction/oligonucleotide ligation assay in a pilot screening of 4476 newborns for cystic fibrosis.

OBJECTIVES: Molecular biological testing for genetic diseases has grown rapidly, but speed, accuracy, specificity, sensitivity, throughput, and cost become more important as large scale screening is considered. This is a pilot study of an assay for the simultaneous detection of up to 31 cystic fibrosis mutations in a multicentre population based screening of 4476 Italian newborns. METHODS: The assay is a polymerase chain reaction, followed by an oligonucleotide ligation assay (PCR/OLA) and finally a sequence coded separation. It allows the detection of up to 31 mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Guthrie spots were used as a source of template DNA. RESULTS: 144 carriers were detected during the analysis of 4476 samples, which translates into a carrier frequency of 1/31.1. Forty two carriers were detected from 1341 samples in Pavia (1/31.9), 53 from 1574 in Turin (1/29.7), and 49 from 1561 in San Giovanni Rotondo (1/31.8). Fifteen different mutations were detected, the most common being delta F508 (0.625). Other common mutations included G542X (16 of 144), which was particularly common in southern Italy (14 of 49), N1303K (8 of 144), and R117H (8 of 144), detected only in the northern centres. CONCLUSIONS: PCR/OLA is a robust, accurate, user friendly method for cystic fibrosis screening of newborns using blood spots in a semiautomated way at a low cost per mutation (0.8 Euro).

Blood Specimen Collection↗

Should children and adolescents undergo genetic testing?

Genetic testing comes in many shapes and sizes. The decision to undergo genetic testing must involve consideration of the medical, psychosocial, and reproductive benefits and risks of testing. The evaluation of risks and benefits varies significantly both between and within families. Pediatricians should keep up with the rapid advances in genetic medicine and the myriad of tests that are being developed and marketed. They also need to be familiar with the psychosocial risks and benefits that these new tests generate for individuals, families and communities. In some situations, genetic testing is merely another diagnostic tool; in other situations, genetic testing offers information about the risks for future diseases. Pediatricians need to be knowledgeable about tests that are indicated clinically and their potential psychosocial implications to best serve children, adolescents, and their families.

Adolescent↗

An update of the mutation spectrum of the survival motor neuron gene (SMN1) in autosomal recessive spinal muscular atrophy (SMA).

Spinal muscular atrophy (SMA) is characterized by degeneration of motor neurons in the spinal cord, causing progressive weakness of the limbs and trunk, followed by muscle atrophy. SMA is one of the most frequent autosomal recessive diseases, with a carrier frequency of 1 in 50 and the most common genetic cause of childhood mortality. The phenotype is extremely variable, and patients have been classified in type I-III SMA based on age at onset and clinical course. All three types of SMA are caused by mutations in the survival motor neuron gene (SMN1). There are two almost identical copies, SMN1 and SMN2, present on chromosome 5q13. Only homozygous absence of SMN1 is responsible for SMA, while homozygous absence of SMN2, found in about 5% of controls, has no clinical phenotype. Ninety-six percent of SMA patients display mutations in SMN1, while 4% are unlinked to 5q13. Of the 5q13-linked SMA patients, 96.4% show homozygous absence of SMN1 exons 7 and 8 or exon 7 only, whereas 3. 6% present a compound heterozygosity with a subtle mutation on one chromosome and a deletion/gene conversion on the other chromosome. Among the 23 different subtle mutations described so far, the Y272C missense mutation is the most frequent one, at 20%. Given this uniform mutation spectrum, direct molecular genetic testing is an easy and rapid analysis for most of the SMA patients. Direct testing of heterozygotes, while not trivial, is compromised by the presence of two SMN1 copies per chromosome in about 4% of individuals. The number of SMN2 copies modulates the SMA phenotype. Nevertheless, it should not be used for prediction of severity of the SMA.

Amino Acid Sequence↗

Microbiology of nontuberculosis mycobacteria.

Recognition of differences, particularly in color and other growth characteristics, between Mycobacterium tuberculosis and other related organisms has led to the identification of the nontuberculosis mycobacteria (NTM). The Runyon Classification, based largely on the presence (or absence) of pigment and rate of growth, was a convenient system for classifying these organisms. Subsequent biochemical analysis has facilitated more precise speciation. However, many of these tests are complex and time consuming and beyond the capacity of most laboratories other than reference centers. The need for accurate identification has become clear because of differences in pathogenicity and treatment between various species and even subspecies of NTM. The recent appearance of rapid diagnostic tests and highly specific genetic identification systems have created new opportunities and challenges with respect to the identification of NTM. This article provides a historic context for the microbiologic study of the organisms, describes key features of the most commonly encountered NTM, notes several important new technical innovations in this field, and considers common clinical issues in relation to the microbiology of NTM.

Bacterial Typing Techniques↗

Categorizing genetic tests to identify their ethical, legal, and social implications.

Practice standards in medical genetics provide an implicit guide to the ethical, legal, and social implications (ELSI) of genetic tests. The common use of nondirective counseling reflects the principle that many testing decisions should be determined by personal values. Yet geneticists make test recommendations in some circumstances, e.g., RET mutation testing for MEN2 and newborn screening for phenylketonuria (PKU). Conversely, many geneticists recommend against testing for Apolipoprotein E (ApoE) alleles to predict Alzheimer disease (AD) risk. Taken together, these examples suggest that genetic tests can be categorized by a joint consideration of clinical validity and availability of effective treatment for persons who test positive. For genetic tests with high clinical validity/no treatment (e.g., presymptomatic testing for Huntington disease), the predominant concern is adequate nondirective counseling to ensure an informed, autonomous decision. By contrast, the predominant concern for tests with high clinical validity/effective treatment (e.g., PKU) is assuring access to care for eligible persons. For tests with limited clinical validity/no treatment (e.g., ApoE), recommending against test use can be justified on the principle of avoiding harm. For a fourth category, tests with limited clinical validity/effective treatment (e.g., HFE mutation testing for hereditary hemochromatosis), net benefit is the issue: the balance between potential benefits of treatment and potential harms of genetic labeling must be weighed. Where uncertainty exists concerning both clinical validity and effectiveness of treatment, as in the case of BRCA 1/2 mutation testing, the value of testing may vary according to different testing contexts. This approach to test categorization allows a rapid determination of the predominant ELSI concerns for different kinds of genetic tests and identifies the data most urgently needed for test evaluation.

Bioethics↗

Psychological support needs for women at high genetic risk of breast cancer: some preliminary indicators.

The number of women in the UK seeking genetic counselling, testing and preventative treatment is rapidly increasing. In Manchester 600-800 women are now referred annually to the Family History Clinic. As yet there is no formal provision for this service within the NHS, but research is underway to evaluate such clinics and to identify the psychosocial sequelae of genetic risk counselling. To date, findings have been based on questionnaire data from which it is difficult to ascertain support needs accurately. We interviewed 158 women 3 months after genetic risk counselling because of a family history of breast cancer. Using standard assessment and diagnostic criteria, 21 (13%) women were diagnosed with an affective disorder. This compared with a prevalence of 26% using the 28 item General Health Questionnaire (GHQ). We did not find a relationship between GHQ distress levels and women's understanding of their risk before genetic counselling, but women with accurate risk knowledge post-counsel had significantly lower GHQ scores than those who continued to over or under-estimate and this finding warrants further investigation. Of women referred for psychological help, few reported risk of breast cancer as their main concern, but themes of loss, unresolved grief and relationship problems were common. The value of the GHQ as a screening instrument is discussed and we suggest a new threshold value based on our analysis. We conclude that risk counselling does not adversely affect the general mental health of attenders but a minority of women may need help with the impact of breast cancer in the family.

Adolescent↗

Genome-wide SNP arrays as a diagnostic tool: clinical description, genetic mapping, and molecular characterization of Salla disease in an Old Order Mennonite population.

An Old Order Mennonite child was evaluated for gross motor delay, truncal ataxia, and slow linear growth. The diagnostic evaluation, which included sub-specialty consultations, neuroimaging, and metabolic testing, was long, costly, and did not yield a diagnosis. Recognition of a similarly affected second cousin prompted a genome-wide homozygosity mapping study using high-density single nucleotide polymorphism (SNP) arrays. SNP genotypes from two affected individuals and their parents were used to localize the disease locus to a 14.9 Mb region on chromosome 6. This region contained 55 genes, including SLC17A5, the gene encoding the lysosomal N-acetylneuraminic acid transport protein. Direct sequencing of SLC17A5 in the proband revealed homozygosity for the 115C --> T (R39C) sequence variant, the common cause of Salla disease in Finland. Three additional affected Mennonite individuals, ages 8 months to 50 years, were subsequently identified by directed molecular genetic testing. This small-scale mapping study was rapid, inexpensive, and analytically simple. In families with shared genetic heritage, genome-wide SNP arrays with relatively high marker density allow disease gene mapping studies to be incorporated into routine diagnostic evaluations.

Agenesis of Corpus Callosum↗

A de novo PABPN1 germline mutation in a patient with oculopharyngeal muscular dystrophy.

BACKGROUND: Oculopharyngeal muscular dystrophy (OPMD) is a late-onset autosomal dominantly inherited disorder characterized by dysphagia, ptosis, and proximal limb weakness and is caused by germline mutations (triplet repeat expansions) in the polyadenylate binding protein nuclear 1 (PABPN1) gene. OBJECTIVE: To describe a 70-year-old female patient with OPMD on the clinical and molecular genetic level and to develop a rapid and efficient molecular genetic screening method to study large patient groups. METHODS: Detailed family history and clinical assessment of the OPMD patient were followed by mutation analysis of the PABPN1 gene by direct DNA sequencing and by our newly developed method, fluorescent PABPN1 polymerase chain reaction (PCR) product (flPPP) method. A cohort of 50 healthy Swiss probands was screened using the flPPP to assess the frequency of the (GCG)7 allele in the Swiss population. Cricopharyngeal myotomy was performed as treatment for dysphagia. RESULTS: A heterozygous (GCG)9 triplet repeat expansion in PABPN1 was identified. Since the family history proved to be negative, the mutation is likely to have occurred de novo. The frequency of the (GCG)7 allele among healthy Swiss controls amounted to 1%. The flPPP method showed a sensitivity and specificity of 100%. Two years after cricopharyngeal myotomy, the patient is still relieved of dysphagia. CONCLUSIONS: An otolaryngologist should include OPMD in the differential diagnosis of a patient presenting with dysphagia, as this symptom can be the first sign of the disease and family history can be negative. Molecular genetic testing represents a highly accurate and rapid way to confirm the clinical diagnosis of OPMD. Cricopharyngeal myotomy relieves the patient of dysphagia in the majority of cases.

Aged↗