Просмотр кода страницы Elective genetic and genomic testing

{{Short description|DNA tests performed without definite indication}}
'''Elective genetic and genomic testing''' are [[DNA]] tests performed for an individual who does not have an [[indication (medicine)|indication]] for testing. An elective [[genetic testing|genetic test]] analyzes selected sites in the [[human genome]] while an elective genomic test analyzes the entire [[human genome]].  Some elective genetic and genomic tests require a physician to order the test to ensure that individuals understand the risks and benefits of testing as well as the results. Other DNA-based tests, such as a [[genealogical DNA test]] do not require a physician's order.  Elective testing is generally not paid for by health insurance companies.  With the advent of [[personalized medicine]],<ref name="AcMedSci">{{cite tech report| title=Stratified, personalised or P4 medicine: a new direction for placing the patient at the centre of healthcare and health education |publisher=Academy of Medical Sciences |date=May 2015 |access-date= 6 Jan 2016 |url=http://www.acmedsci.ac.uk/download.php?f=file&i=32644 }}</ref> also called [[precision medicine]], an increasing number of individuals are undertaking elective genetic and genomic testing.

==History==
[[Genetic testing]]<ref>{{cite book | author = National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Health Care Services; Board on the Health of Select Populations; Committee on the Evidence Base for Genetic Testing. | title = An Evidence Framework for Genetic Testing | publisher = The National Academies Press | date = March 2017 | pmid = 28418631 | doi = 10.17226/24632 | url = https://www.nap.edu/read/24632/chapter/1 | isbn = 978-0-309-45329-5 }}</ref> for a variety of disorders has seen many advances starting with [[cytogenetics]] to evaluate human [[chromosome]]s for [[aneuploidy]] and other [[chromosome abnormalities]].<ref>{{cite journal | vauthors = Moorhead PS, Nowell PC, Mellman WJ, Battips DM, Hungerford DA | title = Chromosome preparations of leukocytes cultured from human peripheral blood | journal = Experimental Cell Research | volume = 20 | issue = 3 | pages = 613–6 | date = September 1960 | pmid = 13772379 | doi = 10.1016/0014-4827(60)90138-5 }}</ref> The development of [[molecular cytogenetics]] involving techniques such as [[fluorescence in situ hybridization]] (FISH) followed,<ref>{{cite journal | vauthors = Dave BJ, Sanger WG | title = Role of cytogenetics and molecular cytogenetics in the diagnosis of genetic imbalances | journal = Seminars in Pediatric Neurology | volume = 14 | issue = 1 | pages = 2–6 | date = March 2007 | pmid = 17331878 | doi = 10.1016/j.spen.2006.11.003 }}</ref> permitting the detection of more subtle changes in the [[karyotype]].<ref>{{cite journal | vauthors = Yunis JJ | title = High resolution of human chromosomes | journal = Science | volume = 191 | issue = 4233 | pages = 1268–70 | date = March 1976 | pmid = 1257746 | doi = 10.1126/science.1257746 | bibcode = 1976Sci...191.1268Y }}</ref><ref>{{cite journal | vauthors = Yunis JJ, Sawyer JR, Ball DW | title = The characterization of high-resolution G-banded chromosomes of man | journal = Chromosoma | volume = 67 | issue = 4 | pages = 293–307 | date = August 1978 | pmid = 357112 | doi = 10.1007/BF00285963 | s2cid = 28588359 }}</ref> Techniques to determine the precise sequence of [[nucleotides]] in [[DNA]] by [[DNA sequencing]], notably [[Sanger sequencing]] was developed in the 1970s.<ref>{{cite journal | vauthors = Sanger F, Nicklen S, Coulson AR | title = DNA sequencing with chain-terminating inhibitors. 1977 | journal = Biotechnology | volume = 24 | pages = 104–8 | date = 1992 | pmid = 1422003 }}</ref> In the 1980s the [[DNA microarray]] appeared, permitting laboratories to find [[copy number variants]] associated with disease<ref name="martin">{{cite journal | vauthors = Martin CL, Ledbetter DH | title = Chromosomal Microarray Testing for Children With Unexplained Neurodevelopmental Disorders | journal = JAMA | volume = 317 | issue = 24 | pages = 2545–2546 | date = June 2017 | pmid = 28654998 | doi = 10.1001/jama.2017.7272 | pmc = 7058144 }}</ref> that are below the level of detection of [[cytogenetics]] but too large to be detected by [[DNA sequencing]].  In recent years the development of [[high throughput biology|high-throughput]] or next-generation sequencing has dramatically lowered the cost of [[DNA sequencing]] permitting laboratories to evaluate all 20,000 genes of the [[human genome]] at once through [[exome sequencing]] and [[whole genome sequencing]].<ref>{{cite web|title=The Cost of Sequencing a Human Genome|url=https://www.genome.gov/sequencingcosts/|website=www.genome.gov|publisher=National Institutes of Health |access-date= 17 Jun 2017}}</ref> A catalogue of the many uses of these techniques can be found in the section: [[genetic testing]].  Most elective genetic and genomic testing employs either a [[DNA microarray]] or next-generation sequencing.

Historically, all [[laboratory test]]s were initiated and ordered by a physician or mandated by a state.  Increasingly, patients and families have become more involved in their own health care.  One outcome has been the growing availability of elective genetic and genomic testing that are initiated by a patient but still ordered by a physician.<ref>{{cite journal | vauthors = Miller KE, Lin SM | title = Addressing a patient-controlled approach for genomic data sharing | journal = Genetics in Medicine | volume = 19 | issue = 11 | pages = 1280–1281 | date = November 2017 | pmid = 28425983 | doi = 10.1038/gim.2017.36 | doi-access = free }}</ref>  Additionally, elective genetic and genomic testing that does not require a physician's order called, direct-to-consumer genetic testing has recently entered the testing landscape.<ref name="genetics">{{cite web |title=What is direct-to-consumer genetic testing?|url=https://ghr.nlm.nih.gov/primer/testing/directtoconsumer |archive-url=https://web.archive.org/web/20160512214713/https://ghr.nlm.nih.gov/primer/testing/directtoconsumer |url-status=dead |archive-date=May 12, 2016 |website=Genetics Home Reference }}</ref>

==Testing categories==
[[Genetic testing]] identifies changes in chromosomes, genes, or proteins; some are associated with human disease. There are many different clinical and non-clinical situations in which genetic testing is used.<ref>{{cite web|title=Genetic Testing: How it is Used for Healthcare|url=https://report.nih.gov/NIHfactsheets/ViewFactSheet.aspx?csid=43|website=www.genome.gov/|publisher=National Institutes of Health|access-date=19 June 2017|archive-date=16 August 2019|archive-url=https://web.archive.org/web/20190816230116/https://report.nih.gov/nihfactsheets/ViewFactSheet.aspx?csid=43|url-status=dead}}</ref>

===Diagnostic testing===
Diagnostic testing is used to identify or rule out a specific genetic or chromosomal condition when a particular disorder is suspected based on signs and symptoms present in the patient.<ref>{{cite web|title=Diagnostic Testing|url=http://www.genesinlife.org/testing-services/testing-genetic-conditions/diagnostic-testing|website=Genes in Life}}</ref> Catalogues of more than 50,000 tests available worldwide can be found at GeneTests<ref>{{cite web|title=GeneTests.org|url=https://www.genetests.org/|website=GeneTests.org|language=en}}</ref> and Genetic Testing Registry.<ref>{{cite web|title=Home - Genetic Testing Registry (GTR) - NCBI|url=https://www.ncbi.nlm.nih.gov/gtr/|website=www.ncbi.nlm.nih.gov|language=en}}</ref>

===Predictive and pre-symptomatic testing===
Predictive and pre-symptomatic testing is carried out in individuals who do not have evidence of the disease under investigation.  This testing includes [[Mendelian]] conditions and polygenic diseases.<ref>{{cite journal | vauthors = Khoury MJ, Janssens AC, Ransohoff DF | title = How can polygenic inheritance be used in population screening for common diseases? | journal = Genetics in Medicine | volume = 15 | issue = 6 | pages = 437–43 | date = June 2013 | pmid = 23412608 | pmc = 4692802 | doi = 10.1038/gim.2012.182 }}</ref>

===Carrier testing===
[[Carrier testing]] is used to identify people who carry one copy of a gene change (also referred to as a variant or mutation) that, when present in two copies, causes a genetic disorder. Carrier testing is typically offered to individuals who are considering pregnancy or are already pregnant, have a family history of a specific genetic disorder and to people in ethnic backgrounds that have an increased risk of specific genetic conditions.<ref>{{cite journal | vauthors = Grody WW, Thompson BH, Gregg AR, Bean LH, Monaghan KG, Schneider A, Lebo RV | title = ACMG position statement on prenatal/preconception expanded carrier screening | journal = Genetics in Medicine | volume = 15 | issue = 6 | pages = 482–3 | date = June 2013 | pmid = 23619275 | doi = 10.1038/gim.2013.47 | doi-access = free }}</ref>

===Pre-implantation genetic diagnosis===
[[Pre-implantation genetic diagnosis]] (PGD)<ref>{{cite journal | vauthors = Geraedts JP, De Wert GM | title = Preimplantation genetic diagnosis | journal = Clinical Genetics | volume = 76 | issue = 4 | pages = 315–25 | date = October 2009 | pmid = 19793305 | doi = 10.1111/j.1399-0004.2009.01273.x | s2cid = 39510284 | url = http://digitool.hbz-nrw.de:1801/webclient/DeliveryManager?pid=5226620&custom_att_2=simple_viewer | url-access = subscription }}{{Dead link|date=September 2025 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> is used in conjunction with [[in-vitro fertilisation|in-vitro fertilization]]. [[in-vitro fertilisation|In-vitro fertilization]] is the process of combining an egg ([[oocyte]]) and sperm outside of the body with intent of fertilization.<ref>{{cite journal | vauthors = Van Voorhis BJ | title = Clinical practice. In vitro fertilization | journal = The New England Journal of Medicine | volume = 356 | issue = 4 | pages = 379–86 | date = January 2007 | pmid = 17251534 | doi = 10.1056/NEJMcp065743 }}</ref> [[Preimplantation genetic diagnosis|PGD]] is the testing of individual oocytes or embryos for a known genetic condition prior to transferring the embryo to the uterus. Used together, IVF and PGD allow for selection of embryos or oocytes presumably unaffected with the condition. [[Preimplantation genetic diagnosis|PGD]] can be utilized by individuals or couples who are affected by a condition of genetic origin, or if both individuals are found to be carriers of a recessive genetic condition.

===Prenatal testing===
[[Prenatal testing]] is diagnostic testing of a fetus before birth to detect abnormalities in the chromosomes or genes. Samples for this testing are obtained through invasive procedures such as [[amniocentesis]] or [[chorionic villus sampling]].<ref>{{cite book | vauthors = Levy B, Stosic M |title=Prenatal Diagnosis |chapter=Traditional Prenatal Diagnosis: Past to Present|journal=<!-- --> |date=2019 |volume=1885 |pages=3–22 |doi=10.1007/978-1-4939-8889-1_1 |pmid=30506187|series=Methods in Molecular Biology |isbn=978-1-4939-8887-7 |s2cid=54566613 }}</ref> Prenatal testing is different from [[prenatal screening]].<ref>{{cite journal | vauthors = Dickerson C | title = An overview of prenatal genetic screening and diagnostic testing | journal = North Carolina Medical Journal | volume = 74 | issue = 6 | pages = 518–21 | year = 2013 | doi = 10.18043/ncm.74.6.518 | pmid = 24316781 | doi-access = free }}</ref>

===Newborn screening===
[[Newborn screening]] screens infants a few days after birth to evaluate for evidence of treatable diseases. Most [[newborn screening]] uses tandem mass spectroscopy<ref>{{cite web|title=Using Tandem Mass Spectrometry for Metabolic Disease Screening Among Newborns|url=https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5003a1.htm|website=www.cdc.gov|publisher=Centers for Disease Control (CDC)}}</ref> to detect biochemical abnormalities that suggest specific disorders. DNA-based newborn testing complements existing newborn screening methods and may replace it.<ref>{{cite journal | vauthors = Berg JS, Agrawal PB, Bailey DB, Beggs AH, Brenner SE, Brower AM, Cakici JA, Ceyhan-Birsoy O, Chan K, Chen F, Currier RJ, Dukhovny D, Green RC, Harris-Wai J, Holm IA, Iglesias B, Joseph G, Kingsmore SF, Koenig BA, Kwok PY, Lantos J, Leeder SJ, Lewis MA, McGuire AL, Milko LV, Mooney SD, Parad RB, Pereira S, Petrikin J, Powell BC, Powell CM, Puck JM, Rehm HL, Risch N, Roche M, Shieh JT, Veeraraghavan N, Watson MS, Willig L, Yu TW, Urv T, Wise AL | display-authors = 6 | title = Newborn Sequencing in Genomic Medicine and Public Health | journal = Pediatrics | volume = 139 | issue = 2 | pages = e20162252 | date = February 2017 | pmid = 28096516 | pmc = 5260149 | doi = 10.1542/peds.2016-2252 }}</ref>

===Pharmacogenomic testing===
[[Pharmacogenomic]] tests (also called [[pharmacogenetics]]) provide information that can help predict how an individual will respond to a medication.<ref>{{cite journal | vauthors = Whirl-Carrillo M, McDonagh EM, Hebert JM, Gong L, Sangkuhl K, Thorn CF, Altman RB, Klein TE | display-authors = 6 | title = Pharmacogenomics knowledge for personalized medicine | journal = Clinical Pharmacology and Therapeutics | volume = 92 | issue = 4 | pages = 414–7 | date = October 2012 | pmid = 22992668 | pmc = 3660037 | doi = 10.1038/clpt.2012.96 }}</ref> Changes in certain genes affect drug [[pharmacodynamics]] (effects on drug receptors) and [[pharmacokinetics]] (drug uptake, distribution, and metabolism). Identifying these changes makes it possible to identify patients who are at increased risk for adverse effects from drugs or who are likely to be non-responders. Pharmacogenomic testing allows healthcare providers to tailor therapies by adjusting the dose or drug for an individual patient.<ref>{{cite web|title=Dosing Guidelines|url=https://www.pharmgkb.org/view/dosing-guidelines.do|website=www.PharmGKB.org|publisher=PharmGKB|access-date=19 June 2017}}</ref><ref>{{cite web|title=Guidelines|url=https://cpicpgx.org/guidelines/|website=www.cpicpgx.org |publisher=Clinical Pharmacogenetics Implementation Consortium|access-date=19 June 2017}}</ref>

===Identity testing===
Identity testing is used to establish whether individuals are related to one another.  It is commonly used to establish [[paternity (law)|paternity]] but can be used to establish relatedness in  adoption and immigration cases.  It is also used in [[forensics]].<ref>{{cite journal | vauthors = Butler JM | title = U.S. initiatives to strengthen forensic science & international standards in forensic DNA | journal = Forensic Science International. Genetics | volume = 18 | pages = 4–20 | date = September 2015 | pmid = 26164236 | pmc = 4573542 | doi = 10.1016/j.fsigen.2015.06.008 }}</ref>

===Ancestry testing===
Ancestry testing (also referred to as [[genetic genealogy]]) allows individuals to establish their country of origin and ethnic background and identify distant relatives and ancestors.<ref>{{cite web|title=What is genetic ancestry testing?|url=https://ghr.nlm.nih.gov/primer/testing/ancestrytesting|archive-url=https://web.archive.org/web/20160727235630/https://ghr.nlm.nih.gov/primer/testing/ancestrytesting|url-status=dead|archive-date=July 27, 2016|website=Genetics Home Reference|publisher=National Institutes of Health|access-date=19 June 2017}}</ref>

===Trait testing===
Some [[phenotypic trait]]s in humans have a well established genetic basis, while others involve [[Polygene|many genes]] or are a [[Quantitative traits|complex mix of genes and environment]].<ref>{{cite web|title=Traits|url=http://learn.genetics.utah.edu/content/basics/traits/|website=Learn.Genetics|publisher=University of Utah}}</ref>

==Technologies==

There are many different types of [[genetic testing]] that exist. Each is designed to look at different types of genetic changes that can occur. At present, no single genetic test can detect all types of genetic changes.

===DNA sequencing===
[[DNA sequencing]] is a method of testing that looks for single letter changes ([[single-nucleotide polymorphisms]]) in the genetic code. It can also determine when a small number of letters are missing (deletions) or extra (duplications). Sequencing may be performed on a single gene, a group of genes (panel testing), most of the coding region or exons (whole exome sequencing), or most of the genome (whole genome sequencing). With time, this technology is expected to be able to detect any abnormality of the human genome.<ref>{{cite journal | vauthors = Chen Y, Zhao L, Wang Y, Cao M, Gelowani V, Xu M, Agrawal SA, Li Y, Daiger SP, Gibbs R, Wang F, Chen R | display-authors = 6 | title = SeqCNV: a novel method for identification of copy number variations in targeted next-generation sequencing data | journal = BMC Bioinformatics | volume = 18 | issue = 1 | pages = 147 | date = March 2017 | pmid = 28253855 | pmc = 5335817 | doi = 10.1186/s12859-017-1566-3 | doi-access = free }}</ref>

===Genotyping===
[[Genotyping]] is testing that looks at specific variants in a particular area of the genetic code. This technology is limited only to those specific variants that the test is designed to detect. [[SNP genotyping]] is a specific form of genotyping.<ref>{{cite web|title=Genotyping SNPs and Other Variants|url=https://www.illumina.com/techniques/popular-applications/genotyping.html|website=Illumina}}</ref>

===Deletion/duplication testing===
Deletion/duplication testing is a type of testing designed to detect larger areas of the genetic code that are missing or extra.<ref>{{cite journal | vauthors = Cheung SW, Bi W | title = Novel applications of array comparative genomic hybridization in molecular diagnostics | journal = Expert Review of Molecular Diagnostics | volume = 18 | issue = 6 | pages = 531–542 | date = June 2018 | pmid = 29848116 | doi = 10.1080/14737159.2018.1479253 | s2cid = 44115796 }}</ref> This technology does not detect single letter variants or very small deletions or duplications.<ref>{{cite journal | vauthors = Li W, Olivier M | title = Current analysis platforms and methods for detecting copy number variation | journal = Physiological Genomics | volume = 45 | issue = 1 | pages = 1–16 | date = January 2013 | pmid = 23132758 | pmc = 3544484 | doi = 10.1152/physiolgenomics.00082.2012 }}</ref>

===<span id="Panel testing"></span>Panel testing===
Panel testing refers to testing for a specific subset of genes most often related to a particular condition. This usually involves sequencing and may also include deletion/duplication analysis. This is often referred to as multigene panel testing because testing simultaneously examines a number of different genes. For example, an individual may have panel testing for a group of genes known to be associated with a particular type of cancer such hereditary colon cancer or hereditary breast and ovarian cancer.<ref>{{cite journal | vauthors = Shah PD, Nathanson KL | title = Application of Panel-Based Tests for Inherited Risk of Cancer | journal = Annual Review of Genomics and Human Genetics | volume = 18 | pages = 201–227 | date = August 2017 | pmid = 28504904 | doi = 10.1146/annurev-genom-091416-035305 }}</ref>

===Array or microarrays===
Array or [[DNA microarrays]] look at copy number changes (missing or extra genetic material).<ref name="martin" /> This testing looks across a large portion of the genome for larger deletions or duplications (also referred to as copy number variation). This technology can not detect single letter changes or very small deletions or duplications.

===Chromosome analysis/karyotype===
Chromosome analysis, also known as [[karyotyping]] refers to testing that assesses whether the expected number of chromosomes are present, whether there is any rearrangement of the chromosomes, and also whether there are any large deletions or duplications. This technology can not detect single letter changes  ([[single nucleotide polymorphism|single nucleotide variants]]) or small deletions or duplications.<ref>{{cite journal | vauthors = Bumgarner R | title = Overview of DNA microarrays: types, applications, and their future | journal = Current Protocols in Molecular Biology | volume = Chapter 22 | pages = Unit 22.1 | date = January 2013 | pmid = 23288464 | pmc = 4011503 | doi = 10.1002/0471142727.mb2201s101 | isbn = 978-0471142720 }}</ref>

===Noninvasive prenatal screening (NIPT) using cell-free fetal DNA ===
[[Prenatal diagnosis|Non-invasive prenatal screening]] screens for specific chromosomal abnormalities such as Down Syndrome in a fetus using [[Cell-free fetal DNA|cell-free DNA]].<ref>{{cite journal | vauthors = Gregg AR, Skotko BG, Benkendorf JL, Monaghan KG, Bajaj K, Best RG, Klugman S, Watson MS | display-authors = 6 | title = Noninvasive prenatal screening for fetal aneuploidy, 2016 update: a position statement of the American College of Medical Genetics and Genomics | journal = Genetics in Medicine | volume = 18 | issue = 10 | pages = 1056–65 | date = October 2016 | pmid = 27467454 | doi = 10.1038/gim.2016.97 | doi-access = free }}</ref> This screening can also provide information about fetal sex and rhesus (Rh) blood type. A blood sample is drawn from the pregnant mother.  This sample contains DNA from the mother and fetus.  The amount of fetal DNA is assessed to determine if there is extra fetal genetic material present that may indicate an increased risk that the fetus has Down Syndrome or other selected conditions. As this is a screening test, other diagnostic tests such as [[amniocentesis]] or [[chorionic villus sampling]] are needed to confirm a diagnosis.

===Newborn screening===
[[Newborn screening]] is a type of testing that assesses risk for certain genetic, endocrine, [[metabolic disorders]], hearing loss and critical congenital heart defects. Each state determines the exact list of conditions that are screened.<ref>{{cite web|title=Conditions Screened by State|url=http://www.babysfirsttest.org/newborn-screening/states|website=www.babysfirsttest.org|publisher=Baby's First Test|access-date=19 June 2017}}</ref> Early detection, diagnosis, and intervention can prevent death or disability and enable children to reach their full potential. The testing is performed from a few drops of blood collected in the newborn period, often by a heel stick.<ref>{{cite web|title=Screening Facts|url=http://www.babysfirsttest.org/newborn-screening/screening-101|website=Baby's First Test|access-date=19 June 2017}}</ref> The exact method of testing may vary but often uses levels of specific analytes present in the blood of the baby. Because this is a screening test, additional testing is often necessary to confirm a diagnosis.

==Pros and cons==
People choose to have genetic testing for many reasons.<ref>{{cite journal | vauthors = Peyron C, Pélissier A, Béjean S | title = Preference heterogeneity with respect to whole genome sequencing. A discrete choice experiment among parents of children with rare genetic diseases | journal = Social Science & Medicine | volume = 214 | pages = 125–132 | date = October 2018 | pmid = 30179780 | doi = 10.1016/j.socscimed.2018.08.015 | s2cid = 52171581 }}</ref><ref>{{cite journal | vauthors = Milko LV, Rini C, Lewis MA, Butterfield RM, Lin FC, Paquin RS, Powell BC, Roche MI, Souris KJ, Bailey DB, Berg JS, Powell CM | display-authors = 6 | title = Evaluating parents' decisions about next-generation sequencing for their child in the NC NEXUS (North Carolina Newborn Exome Sequencing for Universal Screening) study: a randomized controlled trial protocol | journal = Trials | volume = 19 | issue = 1 | pages = 344 | date = June 2018 | pmid = 29950170 | pmc = 6022715 | doi = 10.1186/s13063-018-2686-4 | doi-access = free }}</ref> Testing may be beneficial whether the test identifies a gene change or not. A negative result can eliminate the need for unnecessary checkups and screening tests in some cases. A positive result can direct a person toward available screening, management or treatment options.<ref>{{cite journal|title=Help Me Understand Genetics Genetic Testing|journal=Genetics Home Reference|date=November 7, 2017|url=https://ghr.nlm.nih.gov}}</ref>

===Pros===
,<ref name="test">{{cite web|title=What is a Genetic Test?|url=http://www.eurogentest.org/index.php?id=622|access-date=2017-11-10|archive-date=2020-10-19|archive-url=https://web.archive.org/web/20201019223745/http://www.eurogentest.org/index.php?id=622|url-status=dead}}</ref><ref name="denver">{{cite web|title=Information about Genetic Testing|url=http://www.ucdenver.edu/academics/colleges/medicalschool/programs/Adult%20Medical%20Genetics/GeneticTestingInfo/Pages/GeneticTestingInfo.aspx#tab-2|access-date=2017-11-10|archive-date=2018-07-01|archive-url=https://web.archive.org/web/20180701042030/http://www.ucdenver.edu/academics/colleges/medicalschool/programs/Adult%20Medical%20Genetics/GeneticTestingInfo/Pages/GeneticTestingInfo.aspx#tab-2|url-status=dead}}</ref><ref name="ghr" />
*Determine an individual's risk to develop a genetic condition. By identifying gene changes that may increase risk to develop a certain condition, a person can be screened earlier and more frequently for the disease and/or could make changes to health habits such as diet and exercise
*Diagnose a genetic condition
*Confirm an existing or suspected clinical diagnosis
*Determine the severity of a disease by identifying the type of genetic mutation
*Help doctors choose the most appropriate medication or treatment plan
*Family planning
*Identify gene changes that could be passed on to children
*Screen embryos or newborn babies for certain genetic conditions. Such a genetic test can help people to make informed choices about their future, such as whether to have a baby, consider an egg or sperm donor, etc.

===Cons===
,<ref name="test" /><ref name="denver" /><ref name="ghr" /><ref name="acmg" /> 
*False security. A negative test result does not mean you do not have the condition or are not at risk. There may be many reasons a test is unable to identify a genetic change.
*Expensive and may not be covered by insurance
*May be seen by insurance companies. No protection to long-term care insurance, disability insurance or life insurance
*Ethical issues. Because genetic testing informs a patient about their genetic information, which is shared with other family members, sometimes a genetic test result may have implications for blood relatives of the person who had testing. See ethical issues/considerations.

==Importance of family history==
A patient's [[family history]] also known as [[genealogy]], can provide important insight into medical conditions within the family.<ref>{{Cite web|url=https://www.nsgc.org/patient/familytree|title=National Society of Genetic Counselors : Family History|website=www.nsgc.org|access-date=2019-06-04}}</ref> Given that many conditions have a genetic component, gathering an accurate family history can provide important information about an individual's personal risk for many diseases. Healthcare providers can use family history information to assess a patient's risk for disease, recommend testing or screening, suggest diet or other lifestyle habits that may help reduce risk, as well as assess risk of passing conditions on to children. When obtaining a family history, it is helpful to gather health information for the following family members: grandparents, parents, siblings, aunts, uncles and first cousins, and children. In the genetic counseling community this is often referred to as a three generation family history.<ref>{{cite journal | vauthors = Widmer C, Deshazo JP, Bodurtha J, Quillin J, Creswick H | title = Genetic counselors' current use of personal health records-based family histories in genetic clinics and considerations for their future adoption | journal = Journal of Genetic Counseling | volume = 22 | issue = 3 | pages = 384–92 | date = June 2013 | pmid = 23242928 | pmc = 4882761 | doi = 10.1007/s10897-012-9557-z }}</ref><ref>{{cite journal | vauthors = Solomon BD, Muenke M | title = When to suspect a genetic syndrome | journal = American Family Physician | volume = 86 | issue = 9 | pages = 826–33 | date = November 2012 | pmid = 23113462 | pmc = 4131944 }}</ref><ref>{{cite journal | vauthors = Beery TA, Shooner KA | title = Family history: the first genetic screen | journal = The Nurse Practitioner | volume = 29 | issue = 11 | pages = 14–25 | date = November 2004 | pmid = 15625490 | doi = 10.1097/00006205-200411000-00005 | s2cid = 26500711 }}</ref>

Important information to gather about the individuals in the family include:
*History of conditions including common conditions like heart disease, diabetes, cancer and known genetic conditions like cystic fibrosis or hemophilia or birth defects
*Specific information about the conditions should include: age of onset, specific type of cancer, risk factors (smoking, exposures)
*Cause and age of death
*[[Ethnic background]]

Some families decide to work together to develop a family history, however, some family members may feel uncomfortable disclosing personal medical information. A number of tools are available to gather family history information. Patients should ask their healthcare provider if their institution has a specific form they prefer to have filled out. The U.S. Surgeon General has created a computerized tool called My Family Health Portrait to help patients [https://phgkb.cdc.gov/FHH/ create a family medical history].

==Ethical issues==
===Informed consent===
{{Unreferenced section|date=August 2017}}
Prior to undergoing elective genetic testing, there are many factors that an individual should consider including the scope of testing and potential results in terms of changes to medical management, risk to family members, and impact on legal and financial matters.<ref>{{cite journal | vauthors = Egalite N, Groisman IJ, Godard B | title = Genetic counseling practice in next generation sequencing research: implications for the ethical oversight of the informed consent process | journal = Journal of Genetic Counseling | volume = 23 | issue = 4 | pages = 661–70 | date = August 2014 | pmid = 24664856 | doi = 10.1007/s10897-014-9703-x | s2cid = 18767586 | doi-access = free }}</ref>

===Family implications===
*Family sharing. The implications of genetic test results for other family members are important to consider in patients considering elective genetic testing. Unlike most other medical tests, genetic testing may reveal health information about the patient as well as his or her family members.<ref>{{cite journal | vauthors = Clayton EW, McCullough LB, Biesecker LG, Joffe S, Ross LF, Wolf SM | title = Addressing the ethical challenges in genetic testing and sequencing of children | journal = The American Journal of Bioethics | volume = 14 | issue = 3 | pages = 3–9 | date = 2014 | pmid = 24592828 | pmc = 3950962 | doi = 10.1080/15265161.2013.879945 }}</ref> This may include information which explains a current medical condition, predicts future disease risk, or impacts risks to the next generation. For this reason, it is advised that patients be counseled about potential familial implications prior to genetic testing and provided with support for discussing their results with family members.
*Nonpaternity/[[Consanguinity]]. In some cases, genetic testing may reveal that an individual's mother or father is not actually a biological parent.  In other instances, testing may reveal that an individual's parents are closely related to each other.  Whether or not this information is reported may differ between testing laboratories.  Due to the potential for psychological harm in unexpectedly receiving this type of result, it is important for individuals undergoing testing to be counseled on the possibility of a finding of nonpaternity or consanguinity.<ref>{{cite journal | vauthors = Botkin JR, Belmont JW, Berg JS, Berkman BE, Bombard Y, Holm IA, Levy HP, Ormond KE, Saal HM, Spinner NB, Wilfond BS, McInerney JD | display-authors = 6 | title = Points to Consider: Ethical, Legal, and Psychosocial Implications of Genetic Testing in Children and Adolescents | journal = American Journal of Human Genetics | volume = 97 | issue = 1 | pages = 6–21 | date = July 2015 | pmid = 26140447 | pmc = 4570999 | doi = 10.1016/j.ajhg.2015.05.022 }}</ref>

===Genetic discrimination===
Many patients are concerned about the possibility of [[genetic discrimination]], the idea that certain individuals or entities would use a patient's genetic information against him or her in order to make employment, insurance policies, or other activities and services difficult or impossible to obtain.  In 2008, a new federal law known as the [http://www.ginahelp.org Genetic Information Nondiscrimination Act (GINA)] went into effect to help prevent such discrimination.  GINA prohibits the use of genetic information to discriminate in health insurance and employment. GINA does not prevent all types of discrimination, however. For companies with fewer than 15 employees, these employment protections do not apply. GINA's protections do not apply to the US military or to federal government employees. Additionally, life, disability, and long-term care insurance policies are not included among GINA's protections. These may still continue to use genetic information to determine one's eligibility for coverage and/or policy premiums. Because of these important exceptions, an individual considering elective genetic testing should discuss the possibility of genetic discrimination with his or her physician or genetic counselor.<ref>{{cite journal | vauthors = Prince AE, Roche MI | title = Genetic information, non-discrimination, and privacy protections in genetic counseling practice | journal = Journal of Genetic Counseling | volume = 23 | issue = 6 | pages = 891–902 | date = December 2014 | pmid = 25063358 | pmc = 4233176 | doi = 10.1007/s10897-014-9743-2 }}</ref> Some individuals choose to have certain insurance policies in place before undergoing whole genome sequencing so as to prevent future discrimination.

===Secondary findings===
When undergoing elective genetic testing, patients may expect to receive a variety of different results.  In addition to results that may explain a particular symptom or answer a specific question the patient may have had, the scope of elective testing may reveal additional information.  These “secondary findings” may include information about increased risk for both treatable and untreatable genetic diseases, carrier status for recessive conditions, and pharmacogenetic information. Most laboratories permit patients and families to decide what types of secondary findings (if any), they would like to receive.<ref>{{cite journal | vauthors = Kalia SS, Adelman K, Bale SJ, Chung WK, Eng C, Evans JP, Herman GE, Hufnagel SB, Klein TE, Korf BR, McKelvey KD, Ormond KE, Richards CS, Vlangos CN, Watson M, Martin CL, Miller DT | display-authors = 6 | title = Recommendations for reporting of secondary findings in clinical exome and genome sequencing, 2016 update (ACMG SF v2.0): a policy statement of the American College of Medical Genetics and Genomics | journal = Genetics in Medicine | volume = 19 | issue = 2 | pages = 249–255 | date = February 2017 | pmid = 27854360 | doi = 10.1038/gim.2016.190 | doi-access = free }}</ref> It is critical that patients understand the scope of potential results from elective testing and have the opportunity to opt in or out of various results.<ref>{{cite journal | vauthors = Jarvik GP, Amendola LM, Berg JS, Brothers K, Clayton EW, Chung W, Evans BJ, Evans JP, Fullerton SM, Gallego CJ, Garrison NA, Gray SW, Holm IA, Kullo IJ, Lehmann LS, McCarty C, Prows CA, Rehm HL, Sharp RR, Salama J, Sanderson S, Van Driest SL, Williams MS, Wolf SM, Wolf WA, Burke W | display-authors = 6 | title = Return of genomic results to research participants: the floor, the ceiling, and the choices in between | journal = American Journal of Human Genetics | volume = 94 | issue = 6 | pages = 818–26 | date = June 2014 | pmid = 24814192 | pmc = 4121476 | doi = 10.1016/j.ajhg.2014.04.009 }}</ref>

===Limitations===
{{Unreferenced section|date=August 2017}}
When considering elective genetic testing, it is important to take into account the type and goals of testing.  Providers and patients should be familiar with differing testing methodologies the potential results from each test.  For many individuals, factors such as test cost, scope, and deliverables, in combination with their specific clinical questions, play into the decision to undergo elective testing.
It is also important to recognize that potential results from elective genetic testing are constrained by the current limits of medical knowledge concerning the association between genetics and human disease.  As knowledge of rare genetic factors that confer high risk, as well as common factors that confer lower risks, increases, we will have the ability to learn more about an individual's current and future health.<ref name="test" /><ref name="denver" /><ref name="ghr">{{cite journal|title=Help Me Understand Genetics Genetic Testing|journal=Genetics Home Reference|date=November 7, 2017|url=https://ghr.nlm.nih.gov/|archive-url=https://archive.today/20120629213754/http://ghr.nlm.nih.gov/|url-status=dead|archive-date=June 29, 2012}}</ref><ref name="acmg">{{cite journal | vauthors = Monaghan KG, Benkendorf J, Cherry AM, Gross SJ, Richards CS, Sutton VR, Watson MS | title = ACMG Policy Statement. Risk categorization for oversight of laboratory-developed tests for inherited conditions | journal = Genetics in Medicine | volume = 15 | issue = 4 | pages = 314–5 | date = April 2013 | pmid = 23348768 | doi = 10.1038/gim.2012.178 | author8 = Laboratory Quality Assurance Committee of the American College of Medical Genetics Genomics | author9 = Professional Practice Guidelines Committee of the American College of Medical Genetics Genomics | doi-access = free }}</ref>

==How do I find a geneticist or genetic counselor?==
Due to their advanced training, genetic counselors have a unique set of skills. Their clinical and psychosocial skills are used to help patients understand their genetic risks, determine which tests are most appropriate for their needs, and explain what the possible test results could mean for both the patient and the family.<ref name="counselors">{{cite web|title=About Genetic Counselors|url=http://aboutgeneticcounselors.com/|publisher=National Society of Genetic Counselors|access-date=19 June 2017}}</ref> Clinical geneticists often work in tandem with a genetic counselor and play an important role in providing genetic testing, interpreting test results, and explaining the results.<ref>{{cite web|title=Role of the Clinical Geneticist|url=https://www.hgsa.org.au/documents/item/11|publisher=HUMAN GENETICS SOCIETY OF AUSTRALASIA}}</ref> Given the ever-increasing number of elective genetic and genomic tests offered and the wide variety of issues raised by these tests (see pros & cons above), discussion with a [[clinical geneticist]] or [[genetic counselor]] may be helpful.<ref name="counselors" /> Directories of genetics professionals can be found through the [[American College of Medical Genetics and Genomics]] and the [[National Society of Genetic Counselors]].

==Future==
Elective genetic and genomic testing will continue to evolve as the cost of genetic testing technology falls and patients become increasingly involved in their own health care. The rapid drop in cost of whole [[exome sequencing]] and [[whole genome sequencing]] in the last five years has resulted in the initiation of several large scale sequencing studies that are systematically evaluating the benefits and limitations of elective genetic and genomic testing.<ref>{{cite journal | vauthors = Linderman MD, Nielsen DE, Green RC | title = Personal Genome Sequencing in Ostensibly Healthy Individuals and the PeopleSeq Consortium | journal = Journal of Personalized Medicine | volume = 6 | issue = 2 | pages = 14 | date = March 2016 | pmid = 27023617 | pmc = 4932461 | doi = 10.3390/jpm6020014 | doi-access = free }}</ref><ref>{{cite web|title=MedSeq|url=http://www.genomes2people.org/the-medseq-project/|website=www.Genomes2people.org|access-date=19 June 2017}}</ref><ref>{{cite journal | vauthors = Green RC, Goddard KA, Jarvik GP, Amendola LM, Appelbaum PS, Berg JS, Bernhardt BA, Biesecker LG, Biswas S, Blout CL, Bowling KM, Brothers KB, Burke W, Caga-Anan CF, Chinnaiyan AM, Chung WK, Clayton EW, Cooper GM, East K, Evans JP, Fullerton SM, Garraway LA, Garrett JR, Gray SW, Henderson GE, Hindorff LA, Holm IA, Lewis MH, Hutter CM, Janne PA, Joffe S, Kaufman D, Knoppers BM, Koenig BA, Krantz ID, Manolio TA, McCullough L, McEwen J, McGuire A, Muzny D, Myers RM, Nickerson DA, Ou J, Parsons DW, Petersen GM, Plon SE, Rehm HL, Roberts JS, Robinson D, Salama JS, Scollon S, Sharp RR, Shirts B, Spinner NB, Tabor HK, Tarczy-Hornoch P, Veenstra DL, Wagle N, Weck K, Wilfond BS, Wilhelmsen K, Wolf SM, Wynn J, Yu JH | display-authors = 6 | title = Clinical Sequencing Exploratory Research Consortium: Accelerating Evidence-Based Practice of Genomic Medicine | journal = American Journal of Human Genetics | volume = 98 | issue = 6 | pages = 1051–1066 | date = June 2016 | pmid = 27181682 | pmc = 4908179 | doi = 10.1016/j.ajhg.2016.04.011 }}</ref> Many of these studies have specifically focused on healthy individuals pursuing elective WES or WGS.

Other driving forces in the adoption of this type of testing include continued social empowerment of patients regarding their own health care and increasing private and government funded sequencing projects focused on better understanding the biological, environment, and behavioral factors that drive common disease with the hope of developing more effective ways to treat and manage disease. The Million Veteran Program is one example of a government funded project aimed at collecting data from veterans using questionnaires, health record information, and blood samples for testing, including genetic testing.<ref>{{cite web|title=U.S. Department of Veterans Affairs|url=https://www.research.va.gov/mvp/|website=Million Veteran Program}}</ref> Aimed at recruiting 1 million or more Americans to participate in the research cohort, The [[Precision Medicine Initiative]] will have a large impact on public awareness of [[precision medicine]] and the importance of using genetic information to treat and manage disease as well as optimize health.<ref>{{cite web |url=https://obamawhitehouse.archives.gov/the-press-office/2015/01/30/fact-sheet-president-obama-s-precision-medicine-initiative |title=FACT SHEET: President Obama's Precision Medicine Initiative |author=<!--Staff writer(s); no by-line.--> |date=January 30, 2015 |access-date=July 26, 2016 |via=[[NARA|National Archives]] |work=[[whitehouse.gov]] |quote=}}</ref>
While elective testing is typically not paid for by health insurance companies, this may change as clinical utility continues to be demonstrated.

Future applications for elective genetic and genomic testing may include:
*Expanded prenatal testing options such as prenatal whole genome sequencing and whole exome sequencing<ref>{{cite journal | vauthors = Best S, Wou K, Vora N, Van der Veyver IB, Wapner R, Chitty LS | title = Promises, pitfalls and practicalities of prenatal whole exome sequencing | journal = Prenatal Diagnosis | volume = 38 | issue = 1 | pages = 10–19 | date = January 2018 | pmid = 28654730 | pmc = 5745303 | doi = 10.1002/pd.5102 }}</ref>
*Routine whole genome sequencing for all newborns<ref>{{cite journal | vauthors = Friedman JM, Cornel MC, Goldenberg AJ, Lister KJ, Sénécal K, Vears DF | title = Genomic newborn screening: public health policy considerations and recommendations | journal = BMC Medical Genomics | volume = 10 | issue = 1 | pages = 9 | date = February 2017 | pmid = 28222731 | pmc = 5320805 | doi = 10.1186/s12920-017-0247-4 | doi-access = free }}</ref>
*Increasing availability of direct to consumer testing options<ref name="genetics" />

== See also ==
* [[Personalized medicine]]
*[[Personal genomics]]
*[[Whole genome sequencing]]
*[[Whole exome sequencing]]
* [[Genetic counseling]]
* [[Genomic counseling]]
* [[List of genetic disorders]]
* [[Genetic Information Nondiscrimination Act]]

== References ==
<!--- See [[Wikipedia:Footnotes]] on how to create references using<ref></ref> tags which will then appear here automatically -->
{{Reflist}}

== Further reading ==
{{refbegin}}
*{{cite book | first1 = Joel T. | last1 = Dudley | first2 = Konrad J. | last2 = Karczewski | title = Exploring Personal Genomics | publisher = Oxford University Press | date = 2013 }}
* {{cite book | first1 = Jeanette J. | last1 = McCarthy | first2 = Bryce A. | last2 = Mendelsohn | title = Precision Medicine: A Guide to Genomics in Clinical Practice | publisher = McGraw-Hill Education | date = 2017 }}
{{refend}}

== External links ==
*[https://archive.today/20120629213754/http://ghr.nlm.nih.gov/ Genetics Home Reference]
*[http://www.ashg.org/education/csertoolkit/index.html Guide to Interpreting Genomic Reports: A Genomics Toolkit] {{Webarchive|url=https://web.archive.org/web/20170416174055/http://www.ashg.org/education/csertoolkit/index.html |date=2017-04-16 }}  
*[https://www.ncbi.nlm.nih.gov/projects/SNP/ dbSNP] (a public-domain archive for a broad collection of simple genetic polymorphisms)
*[https://www.snpedia.com/index.php/SNPedia/ SNPedia] {{Webarchive|url=https://web.archive.org/web/20190322152137/https://www.snpedia.com/index.php/SNPedia |date=2019-03-22 }} (a wiki-based bioinformatics web site that serves as a database of single nucleotide polymorphisms and peer-reviewed scientific publications associated with the variants)

<!--- Categories --->
[[Category:Genetics]]