Importance of the Genetics Counselling - Term Paper Example

Genetic counseling is a counseling process that deals with the disorders within the family. This process involves a counselor that helps the family or the person; (a) discusses the medical fact and informs about the diagnosis and the cause of disorder and the cure; (b) informs the way heredity can cause disorders and the individuals in the family that possess risk; (c) understand the cure but keeping in mid about the comeback of the disease; (d) choose the cure which they find appropriate keeping in mind the risk and the family goals and act accordingly to the decision; and (5) tries to make the best arrangement to adjust in family due to disorder and/or to the risk of reappearance of that disorder.(16) 1. Origin, Nature, and Goals of Genetic Counseling In 1947, the term genetic counseling was introduced to describe the relationship between clinical geneticists and those to whom they provide information about the etiology, natural history, and recurrence risks of hereditary disorders. The term was intended to promote a respectful attitude toward the diverse values and goals of those counseled and to avoid the connotation with eugenics that had been associated with genetic practices of the past. The contemporaneous development of Rogerian psychology contributed to the nondirective approach that was characterized in 1974 as the norm of genetic counseling. This norm was consistent with the goal of early purveyors of genetic information, basic scientists, who were accustomed to conveying information without giving advice (23). 2. Genetics Counselling Programme: Its importance 2.1 Reproductive decision-making: Some studies have defined effectiveness as impact on reproductive decision-making, leading to a potential reduction in affected births(4). Hildes at al. for example, reported a pilot neonatal screening programme for Duchenne muscular dystrophy (DMD), offering prenatal diagnosis for future pregnancies in at risk women. However, prenatal diagnosis was only actually carried out in two out of seven subsequent pregnancies. The authors conclude that such programmes ``may not be an effective way of decreasing the number of repeat cases of DMD within families'' (18). Another study (39), of clients reported reactions to genetic counselling, found that almost half (43.5%) of 628 clients completing questionnaires 6 months after their counselling session reported that their reproductive plans had been influenced. However, the change and stability of reproductive plan patterns of both groups -self-described influenced and not influenced -were similar. Such an approach is always likely to be contentious because of its thinly veiled eugenicism. This has led to a search for other possible outcome measures. 2.2 Information recall: Swerts (2), for instance, looking at the impact of both genetic counselling and prenatal diagnosis for Downs syndrome (DS) and neural tube defects (NTD), adopted a simple information-delivery model, assessing effectiveness by measuring recipients' recall rather than their subsequent reproductive decisions. Measurements of knowledge acquired or information recalled after counselling are frequent proxies for effectiveness, reflecting the common attempt to avoid the stigma of eugenics by presenting counselling as an educational intervention to enhance recipients' autonomy. A number of studies have compared `before' and `after' knowledge of genetic factors (4) amongst various client groups. 2.3 Anxiety reduction: Genetic testing has a potential to raise anxiety among those tested. Mennie et al. (24) found that, compared with controls identified as non-carriers, CF carriers and their partners showed a significant increase in generalized psychological disturbance over a 4-day period awaiting the partners' test results. This was attributed to anxiety and depression. After the results had been disclosed, both parties returned to their control levels. Watson et al. (38)also examined anxiety in those being screened to ascertain their CF carrier status. The authors report that counselling had mostly allayed this when couples were interviewed 6 months after the initial test. However, since the screening was simply to determine (asymptomatic) carrier status, which is not necessarily problematic in reproductive terms, this seems likely to have had an impact on expressed anxiety. Other researchers (20)detected no anxiety among a general population cohort screened for CF carrier status. A study (14) of the psychological impact of amniocentesis in three risk groups (older mothers, mothers who had a previous child with DS, and mothers who had a previous child with NTD) found anxiety levels in relation to the test both differed between the groups and showed considerable variation within each. Different screening or testing programmes clearly have different implications for the participants, and there are no easy comparisons to be made or conclusions drawn. Although most literature in this area relates to genetic testing, some studies do focus directly on counselling. One examined the impact of different counselling formats on mood (15).A psychological scale administered before and after counselling assessed mood change. The authors concluded that the use of different formats made no significant differences to mood, although there is no discussion of what the changes actually were. Cull et al. (10) carried out a similar assessment of differing counselling formats using the Spielberger state-trait anxiety inventory, and also found no significant differences between groups. Another study examined both clients' expectations of counselling and its psychological impact, again using the Spielberger inventory (26). There was reduced adverse psychological impact when patient expectations were met in the counselling session. All these studies, however, are concerned with comparisons of counselling methods rather than counselling itself. The only study identified which explicitly focused on anxiety levels as a result of counselling concerned familial breast cancer (21). Counsellees had higher breast cancer specific distress rates after counselling than before, despite being more informed. The potential for counselling to be a worrying or threatening experience is underlined. As Jarman (3) has pointed out, counselling may also have adverse psychological impacts on counsellors, an issue that does not yet seem to have attracted investigators. Nevertheless, anxiety reduction among those tested may be one of the less contentious outcome measures. 2.4. Client satisfaction: The importance is also been defined in terms of clients satisfaction. In one study, 36 individuals who had received counselling for cancer were asked to rate their satisfaction both with the care provided by the clinical geneticist they had seen, and with general procedures at the clinic (5). In another, clients were asked to rate counselling sessions in terms of clarity, depth of discussion and their willingness to raise issues; the ratings were examined for evidence of influence from the sex of the counsellor (41). However, both studies acknowledged the limitations of their approach, stressing the importance of relating such findings to qualitative analysis of the actual counselling sessions. Reported satisfaction is a questionable measure of process, since it does not necessarily relate to what actually occurred during the session. As Clarke et al. (9) highlight, while research has focused on outcome, effectiveness is also fundamentally related to process. In their view, while outcome measures are valid in a research context, they are useless in practice, a position echoed by other commentators who argue that outcome measures used alone are both inappropriate and methodologically inadequate(31). 3. Structural and numerical abnormalities The chromosome abnormalities that karyotyping might detect in the fetus are of two types, numerical or structural. Numerical abnormalities involve the gain or loss of one or more chromosomes. This form of abnormality is termed aneuploidy. The presence of a single extra chromosome is referred to as trisomy and the presence of two or more sets of chromosomes is referred to as polyploidy (1). The other main type of abnormality detected consists of structural chromosome rearrangements, and these result from chromosome breakage with subsequent reunion in a different configuration. These abnormalities include translocations, which involve the exchange of genetic material between chromosomes. The most common abnormalities diagnosed prenatally are aneuploidies such as trisomy 21 (Down syndrome), trisomy 18 (Edward syndrome), trisomy 13 (Patau syndrome), and X and Y sex chromosome aneuploidies(12). Together these account for up to 95% of live-born chromosomal abnormalities(40). Statistics on the occurrence of the various chromosome abnormalities are complicated by the fact that certain abnormalities have such serious consequences that the chances of survival for the fetus are seriously compromised. Available data on occurrence of different abnormalities are therefore sometimes presented in relation to the number of births (with or without stillbirths), at other times in terms of pregnancies, or sometimes in relation to numbers of amniotic samples tested. Table 1. Chromosome abnormalities commonly detected, their frequency and consequences (17). Chromosome number, size, and shape constitute the karyotype. Although every karyotype is different for each organism, every cell in every organism has the same karyotype. Chromosomal aberrations can be divided into 2 categories: numeric and structural (Figs 1C, D). (29) Numeric alterations result in the addition (trisomy or triploidy) or loss (monosomy or aneuploidy) of a chromosome. Structural changes occur between and within chromosomes. Regions between chromosomes can be traded (translocation) or donated from one to the other (insertion). Within the same chromosome, regions can be lost (deletion), duplicated (amplification), or reversed (inversion). The identification of these structural changes represents a continual technical challenge and an important component of medical diagnosis and genetic counseling.(29) Figure: 1. Diagrammatic representation of chromosomes and their structural alteration. A, Chromosomes 3 and8 stainedwith giemsa (G-banding) at a resolution of the 400 bandlevel. Each chromosome has a short (p) and long (q) arm that is separated by a centromere at 1 end and a telomere at the other. Chromosomes are described as metacentric (chromosome 3) or acrocentric (chromosome 8), depending on the position of the centromere. Bands and sub-bands are numbered from the centromere outward. B, Structural aberrations involving 2 chromosomes. Illustrated is a fragments from chromosomes 3 (yellow) and8 (blue) undergoing translocation [t (3;8)(p21-pter;p21-pter)] and insertion [ins (3;8)(q21.2-21.3;q13.3-22)]. C, Structural alterations involving a single chromosome illustrated (using chromosome 3) include amplification [dup(3)(p21-pter)], inversion [inv(3)(p21-pter)], and deletion [del(3)(p21-pter)].(29) Figure 2: The human karyotype and aberrations. A, The normal human karyotype consists of 46 chromosomes (23 pairs). Autosomes are chromosome pairs 1-22. The sex chromosomes consist of a pairing of the X andY chromosomes (XX _ female; XY _ male). B, Each chromosome is composedof 2 chromatids. At the endof each chromatidis the telomere. The centromere (“clear zone”) is foundin a centric or paracentric position. C, Numeric aberrations of the human karyotype appear in many diseases and syndromes. Most commonly, the change is an addition (trisomy) of loss (aneuploidy) of a chromosome. Down syndrome is an important example. D, Structural alterations are another important chromosomal aberration. Many types of structural alterations exist in human disease and syndromes. The Philadelphia chromosome, found in chronic myelogenous leukemia, is an important example and a major prognostic factor.(29) 4. Methods used in Genetic Counseling Program 4.1 Amniocentesis Amniocentesis is one of several diagnostic tests that are carried out for the mothers undergoing Genetic counseling. It detects the chromosome disorders that can occur in the unborn child. In this process, a sample of the fluid from the amnion is removed and than tested for disorders like Down`s syndrome, anemia etc. This test is carried out from the fifteenth week till the pregnancy. The amniotic fluid is used for different tests in the laboratory like karyotyping etc 4.2 Karyotyping. For prenatal diagnosis the methods that are used in Genetic Counseling mainly are classified into two categories; Conventional Genetics and Molecular Cytogenetics.(34) 4.2.1 Conventional Cytogenetics A karyotype may be defined as the accurate organization (matching and alignment) of the chromosomal content of any given cell type. In a karyotype, chromosomes are arranged and numbered by size, from the largest to the smallest. Karyotype is the normal nomenclature used to describe the normal or abnormal, constitutional or acquired chromosomal complement of an individual, tissue or cell line. The conventional cytogenetic techniques are used routinely for the determination of numerical chromosomal abnormalities or structural rearrangements, mainly translocations(28). Advantages: A conventional cytogenetic study is still widely regarded as being the gold standard for genetic tests, since it is the best one currently available for assessing the whole karyotype at one time. Moreover, it is inexpensive.(28) Disadvantages: Only dividing cells can be assessed, there is a need of metaphases stage cells. No frozen tissue can be used. Moreover, it is consuming method and due to the lack of automation in sample processing, the time needed to analyze each division is very long. One finds it difficult to analyze and interpret data. And there is a need of experienced cytogenetic specialist to interpret the results(28). Table 2: Molecular genetic techniques commonly used for prenatal diagnosis.(34) 4.2.2 Molecular Cytogenetics Although Karyotyping remains the gold standards of chromosome analysis and still is the most frequently used genetic method in prenatal diagnosis, the most important advance in cytogenetics during the past 20 years has been the development of fluorescence in situ hybridization (FISH) technologies (34). Further, refinements in cytogenetic techniques over the past 30 years have allowed the increasingly sensitive detection of chromosome abnormalities. In particular, the advent of fluorescence in situ hybridization techniques has provided significant advances in both diagnosis and research. The application of new multicolour karyotyping techniques has allowed the complete dissection of complex chromosome rearrangements and provides the prospect of identifying new recurrent chromosome rearrangements. Both comparative genomic hybridization and interphase fluorescence in situ hybridization avoid the use of metaphase chromosomes altogether and have allowed the genetic analysis of previously intractable targets. Recent developments in comparative genomic hybridization to DNA microarrays provide the promise of high resolution and automated screening for chromosomal imbalances. Rather than replacing conventional cytogenetics, however, these techniques have extended the range of cytogenetic analyses when applied in a complementary fashion.(19) 4.2.2.1. FISH Background: FISH is the most common practice in Molecular Cuytogenetics. FISH was first introduced in clinical cytogenetics in the USA in 1988, 45 following which there was a rapid development in the technology.46 The test was first introduced into the UK in 1991.47 The technique uses chromosome-specific probes with fluorescent labels attached; these probes are now available in commercial kit form. Detection requires microscope systems, which may range from simple fluorescence microscopes to more expensive image analysis systems such as microscope and cooled charged-coupled device cameras. FISH is a less labour-intensive test than the current karyotyping technique.(17) History of the FISH test in prenatal diagnosis: Early FISH studies on uncultured amniocytes made use of single chromosome-specific probes (e.g. for chromosome 21). However, these first probes (centromeric repetitive or alphoid) were found to show cross-hybridisation between certain chromosomes (for example, the two probes interacted for chromosomes 13 and 21). This discovery led to the development of different types of probe (chromosome cosmid contig probes and YACs). The use of the first of these to detect Down syndrome (trisomy 21) was successfully demonstrated in a prospective study of 500 uncultured amniotic fluid samples as early as 1994.48 Around 2 years later, the YAC probes started to be used in the UK to provide rapid preliminary reports on samples (Lowther G, Duncan Guthrie Institute of Medical Genetics, Glasgow: personal communication, 1996). At the same time, it was demonstrated that a combination of five FISH probes could be used to examine all five chromosomes most commonly associated with chromosomal abnormalities (21, 18, 13, X, Y) in a single* multicolour FISH hybridisation experiment.3 Subsequently, 5-probe FISH test kits were developed and marketed by commercial manufacturers (17). Figure 3. Diagram of the procedure for FISH. (7) The FISH-based karyotyping of chromosomes has resulted in several novel techniques, such as multicolour FISH (MFISH) and SKY FISH. Spectral karyotyping methods use fluorescent dyes that bind to specific regions of chromosomes. By using a series of specific probes each with varying amounts of dyes, different pairs of chromosomes have unique spectral characteristics (28). There is a broad array of FISH techniques for both diagnostic and research applications. The increasing availability of commercial probes means that most clinical laboratories now use FISH as an adjunct to cytogenetic diagnosis. Metaphase FISH with specific gene probes provides an accurate assessment of rearrangements with a defined diagnostic or prognostic value, and interphase FISH provides the possibility of analysis on samples that would otherwise fail. One of the most significant advances has been in the development of multicolour FISH technologies which has culminated in FISH-based karyotyping methods. Metaphase CGH provides a global screening approach allowing the analysis of samples previously intractable to cytogenetic analysis. More recently, the development of CGH to DNA (or cDNA) microarrays provides the prospect for automated screening (19). Advantages: FISH is a very rapid, sensitive, and cost-effective technique that offers the capability to detect both numerical and structural chromosomal abnormalities in interphase and metaphase nuclei, and also FISH permits rapid sex determination. (28). Limitations: However, FISH has some limitations like cross-hybridization of non-specific fluorescence signals, non-specific background, and suboptimal signal intensity. Small deletions, duplications and inversions cannot be detected with painting probes (28). 4.2.2.2 Multicolour Whole-chromosome Painting (M-FISH AND SKY) One of the most appealing aspects of FISH is the ability to identify several targets simultaneously using different colours (multicolour FISH). As early as 1989, three targets could be visualized simultaneously (27). By the early 1990s this had increased to the simultaneous detection of 7±12 different probes in different colours.(11, 30). However, it was not until 1996 that developments in probe labeling and digital imaging systems allowed the visualization of the entire chromosome complement in 24 different colours (32, 33). The two techniques, M-FISH and SKY, both use DOP-PCR amplification of flow-sorted chromosomes and a `combinatorial' labelling approach. The principle behind this is the generation of more colours than there are fluorochromes available, by labelling with 1:1 mixtures of fluorochromes. The theoretical number of targets which can be discriminated in this manner is 2n=1, where n is the number of fluorochromes available. Using only five fluorochromes, this allows painting of the entire chromosome complement in 24 colours (See Figure: 5). Figure 5. M-FISH colour karyotype of a bone marrow metaphase from an AML patient. G-banding identified a balanced t(1;3)(p32;p13), and this was confirmed by M-FISH (arrows). However, M-FISH also identified a cryptic der(6)t(6;22) not visible by G-banding (arrow). Two copies of the der(6) are present in this cell (19). M-FISH and SKY differ only in the imaging system used to discriminate the fluorochrome combinations. M-FISH relies on capturing the separate fluorochrome images for each of the five fluorochromes using specifically selected narrow bandpass filter sets (13, 33). SKY uses a single exposure of the image and a combination of cooled charge coupled device (CCD) imaging and Fourier transform spectrometry to analyse the spectral signature of the fluorochrome combinations.(32). Both use dedicated software to translate the unique labelling combination for each chromosome into a pseudocolour. Both of these techniques have already demonstrated hidden chromosome rearrangements in complex karyotypes in tumour cell lines and in haematological malignancies.(33, 35, 37). Disadvantages: In common with other whole-chromosome painting methods, both M-FISH and SKY are unable to detect small intrachromosomal rearrangements (inversions, deletions, duplications). In particular, the limit of resolution for telomeric rearrangements is 2±2.5 Mb.(6, 36). Additionally, complementary FISH approaches are required to overcome these limitations. In addition to that latest reports state that although M-FISH and SKY have proved to be extremely useful in prenatal, postnatal, and cancer cytogenetics. However, these technologies have inherent limitations that, in certain situations, may result in chromosomal misclassification. Most multicolor karyotyping errors have a similar mechanistic basis. Structural rearrangements, which juxtapose nonhomologous chromosome material, frequently result in overlapping fluorescence at the interface of the translocated segments, a phenomenon sometimes referred to as “flaring”(22). This flaring effect can obscure or distort the fluorescence pattern of adjacent chromatin, leading to misinterpretation by the multicolor karyotyping systems.(8) 4.2.2.3 Comparative genomic hybridization (CGH) CGH is a method that gives an overview of the whole genome and allows the detection of DNA copy number changes. Since its first description it has become a powerful alternative to chromosome banding and FISH. This technique allows a genome screening of chromosomal imbalances without prior knowledge of genomic regions of interest. CGH is an alternative method to reveal unbalanced chromosomal changes that may occur in hESCs lines during long-term cultures, especially when it is difficult to obtain good quality metaphases.(28) Figure 6. Representative CGH ideogram profile for chromosome 1. The ideogram indicates a surplus of the whole chromosomal material (n ¼ 22 chromosomes analysed), shown as a green bar along the whole q-arm.(28) Figure 7: Comparison of cytogenetic techniques for identifying chromosomal abnormalities. (25) Although the advances of the techniques utilized in Genetic counseling are major; all of them come with their own share of advantages and disadvantages. The same is summarized in the Table 4. Table 4: Advantages and disadvantages of the different cytogenetic techniques Cytogenetics techniques Advantages Disadvantages CONVENTIONAL CYTOGENETICS Karyotyping Inexpensive (< 100 USA $/sample). Only dividing cells can be assessed, need of metaphases, no frozen tissue can be used Inexpensive, easy-to-acquire equipment Time consuming method, due to the lack of automation in sample processing and the time needed to analyse each division Difficult to analyse and interpret data Need of experienced cytogenetic specialist MOLECULAR CYTOGENETICS FISH Medium cost (_100 USA $/ sample) Need to know in advance the chromosomal abnormality we are looking for Technically non-demanding methodology It is not a screening technique Rapid, sensitive and easy analysis/data interpretation Feasible to do on frozen tissue, this technique offers the capability to use in interphase and metaphase nuclei M-FISH High resolution (in the range of 1.5 Mb) Costly (>US$100/sample). Overall view of all chromosomes in a single assay This technique can be performed only on metaphase spreads Not feasible to do on frozen tissue Need experienced cytogenetic specialist Difficult to analyse and interpret data Expensive, non-affordable equipment CGH Medium cost (_US$100/sample) No need for metaphases. CGH requires only the Need of experienced cytogenetic specialist Difficult to analyse and interpret data genomic DNA Feasible to do on frozen tissue Expensive, non-affordable equipment SKY High resolution (in the range of 1.5 Mb) Costly (>US$100/sample) Overall view of all chromosomes in a single assay This technique can be performed only on metaphase spreads No feasible to do on frozen tissue Need experienced cytogenetic specialist Difficult to analyse and interpret. 5. Summary: The expected explosion in genetic information will present tremendous challenges for genetic counseling, no matter who provides it. Medical professionals already find it difficult to absorb and retain genetic information outside their own field of expertise. Some are uncertain when to begin offering tests that enter the market, considering themselves vulnerable to legal action if an affected child is born to parents who were not offered an assay that might have been used. Eventually, expanded diagnostic ability will lead to more effective intervention and treatment, but not without false starts and premature characterizations. Questions about which disorders to diagnose and when to do so (e.g. premarital, pre conceptional, fetal, childhood, adulthood) will persist. The current practice of one-on-one verbal counseling between families and genetic counselors cannot accommodate the enormous amount of information that will be available to families. Alternative strategies must therefore be considered. These include group counseling, educational videotapes and brochures, internet access, and paramedical counselors trained to deal with one or only a few disorders in a well-defined context. Minimally, primary health care providers will be expected to provide a large portion of the routine counseling, identifying individuals requiring more sophisticated services from specialists (23). 6. References: 1. 1990. Mosby’s dictionary of medicine, nursing and allied health. The CV Mosby Company, St Louis, MI. 2. A., S. 1992. Impact of genetic counselling and prenatal diagnosis for down syndrome and neural tube defects. Birth Defects Original Article Series 23:61-83. 3. AL., J. 1983. Confessions of a genetic counsellor. Prenatal Diag 3:270. 4. Alison Pilnick, R. D. 2001. Research directions in genetic counselling: a review of the literature. Patient Education and Counselling 44:95-105. 5. Bleiker E, A. N., Menko F. . 1992. 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Karyotyping human chromosomes by combinatorial multi-¯uor FISH. Nature Genetics 12:368-375. 34. The Hung-Bui, M. N., Elizabath Blennow. 2002. Prenantal Diagnosis: Molecular Genetics and Cytogenetics. Best Practice & Research Clinical Obstetrics and Gynaecology 16:629-643. 35. Tosi S, G. G., Rambaldi A et. 1999. Characterisation of the human myeloid leukaemia-derived cell line GF-D8 by multiplex fluorescence in situ hybridisation, subtelomeric probes and comparative genomic hybridisation. Genes, Chromosomes and Cancer 24:213±221. 36. Uhrig S, S. S., Fauth C. , and 1999. Multiplex-FISH for pre- and postnatal diagnostic applications. American Journal of Human Genetics 65:448-462. 37. Veldman T, V. C., Schrck E . 1997. Hidden chromosome abnormalities in haematological malignancies detected by multicolour spectral karyotyping. Nature Genetics 15:406-410. 38. Watson EK, M. E., Lamb J. . 1992. Psychological and social consequences of community carrier screening programme for cystic fibrosis. 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