{"id":1045,"date":"2016-11-21T09:03:19","date_gmt":"2016-11-21T08:03:19","guid":{"rendered":"https:\/\/cegat.net\/web\/en\/?post_type=encyclopedia&#038;p=1045"},"modified":"2023-06-20T10:27:30","modified_gmt":"2023-06-20T09:27:30","slug":"positive-predictive-value-ppv","status":"publish","type":"encyclopedia","link":"https:\/\/www.cenata.de\/en\/encyclopedia\/positive-predictive-value-ppv\/","title":{"rendered":"Positive Predictive Value (PPV)"},"content":{"rendered":"<p>The PPV reflects the rate of positive test results that are confirmed by <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/chromosome\/\" target=\"_self\" title=\"A chromosome is an complex of tightly-coiled DNA and the proteins which hold the structure together. Normal human cells contain 23 pairs of chromosomes - 22 autosomes and the X and Y sex chromosomes.\" class=\"encyclopedia\">chromosome<\/a> analysis or after birth.<\/p>\n<p>The risk of the presence of a <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/fetal\/\" target=\"_self\" title=\"Relating to the unborn child\" class=\"encyclopedia\">fetal<\/a> <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/trisomy-21\/\" target=\"_self\" title=\"Trisomy 21 is the most common numerical chromosomal disorder in newborns. There are three copies of chromosome 21 and this leads to the development of Down syndrome.\" class=\"encyclopedia\">trisomy 21<\/a> during pregnancy is approximately 1:500 for the average population. Almost all of these cases are correctly detected by the Harmony<sup>&reg;<\/sup> test (detection rate 99.3%[1.Stokowski R, Wang E, White K, Batey A, Jacobsson B, Brar H, Balanarasimha M, Hollemon D, Sparks A, Nicolaides K, Musci TJ.: Clinical performance of non-invasive prenatal testing (<a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/nipt\/\" target=\"_self\" title=\"Non-invasive prenatal tests are molecular genetic analyses in prenatal diagnostics to detect fetal chromosomal anomalies from the maternal blood, avoiding the risk of miscarriage inherent in more invasive methods.\" class=\"encyclopedia\">NIPT<\/a>) using targeted cell-free <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/dna\/\" target=\"_self\" title=\"Deoxyribonucleic acid: biomolecule and carrier of genetic information\" class=\"encyclopedia\">DNA<\/a> analysis in maternal plasma with <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/microarray\/\" target=\"_self\" title=\"Technology that can use very small amounts of starting material (DNA or RNA) to analyse the expression of thousands of genes simultaneously.\" class=\"encyclopedia\">microarray<\/a>s or next generation sequencing (NGS) is consistent across multiple controlled clinical studies. Prenat Diagn. 2015 Sep 1]). However, if one in every 2500 Harmony<sup>&reg;<\/sup> test result for <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/trisomy-21\/\" target=\"_self\" title=\"Trisomy 21 is the most common numerical chromosomal disorder in newborns. There are three copies of chromosome 21 and this leads to the development of Down syndrome.\" class=\"encyclopedia\">trisomy 21<\/a> is false positive, this corresponds to a total of approximately every fifth (2500\/500) positive <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/trisomy-21\/\" target=\"_self\" title=\"Trisomy 21 is the most common numerical chromosomal disorder in newborns. There are three copies of chromosome 21 and this leads to the development of Down syndrome.\" class=\"encyclopedia\">trisomy 21<\/a> result. The so-called &ldquo;Positive Predictive Value&rdquo; (PPV) for <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/trisomy-21\/\" target=\"_self\" title=\"Trisomy 21 is the most common numerical chromosomal disorder in newborns. There are three copies of chromosome 21 and this leads to the development of Down syndrome.\" class=\"encyclopedia\">trisomy 21<\/a> is therefore approximately 80% for a middle-aged woman.<\/p>\n<p>Since the risk of <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/trisomy-21\/\" target=\"_self\" title=\"Trisomy 21 is the most common numerical chromosomal disorder in newborns. There are three copies of chromosome 21 and this leads to the development of Down syndrome.\" class=\"encyclopedia\">trisomy 21<\/a> depends to a large extent upon the age of the mother, this must be included in the calculation of the positive predictive value. For a 40-year-old woman with a risk of approximately 1:100 of giving birth to a child with <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/trisomy-21\/\" target=\"_self\" title=\"Trisomy 21 is the most common numerical chromosomal disorder in newborns. There are three copies of chromosome 21 and this leads to the development of Down syndrome.\" class=\"encyclopedia\">trisomy 21<\/a>, only one in every 25. (2500\/100) positive Harmony<sup>&reg;<\/sup> test reports a false positive <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/trisomy-21\/\" target=\"_self\" title=\"Trisomy 21 is the most common numerical chromosomal disorder in newborns. There are three copies of chromosome 21 and this leads to the development of Down syndrome.\" class=\"encyclopedia\">trisomy 21<\/a>, thus the PPV of approximately 97% is correspondingly high.<\/p>\n<p>The following Figure explains the calculation:<\/p>\n<figure id=\"attachment_941\" aria-describedby=\"caption-attachment-941\" style=\"width: 300px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.cenata.de\/wp-content\/uploads\/2021_PPV-Berechnung_EN_-scaled.jpg\"><img decoding=\"async\" class=\"wp-image-941 size-medium\" src=\"https:\/\/www.cenata.de\/wp-content\/uploads\/2016\/11\/ppv-300x130.jpg\" alt=\"Figure 1: Calculation of the Positive Predictive Value (PPV)\" width=\"300\" height=\"130\"><\/a><figcaption id=\"caption-attachment-941\" class=\"wp-caption-text\">Figure 1: Calculation of the Positive Predictive Value (PPV)<\/figcaption><\/figure>\n<p>By comparison: the PPV of traditional <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/first-trimester-screening\/\" target=\"_self\" title=\"A combination of a special ultrasound test (measuring nuchal translucency and possibly other factors such as nasal bone size) and a biochemical analysis of PAPP-A (Pregnancy-associated plasma protein A) and free &beta;-hCG (&szlig;-chain of the human chorionic gonadotropin) in the mother's blood serum. The test can be performed between weeks 11+0 and 14+0 of a&hellip;\" class=\"encyclopedia\">first-trimester screening<\/a> is only approximately 5 &ndash; 7%. This means that only 1 out of 18 abnormal results are confirmed by an invasive diagnosis; in 17 out of 18 cases, traditional <a href=\"https:\/\/www.cenata.de\/en\/encyclopedia\/first-trimester-screening\/\" target=\"_self\" title=\"A combination of a special ultrasound test (measuring nuchal translucency and possibly other factors such as nasal bone size) and a biochemical analysis of PAPP-A (Pregnancy-associated plasma protein A) and free &beta;-hCG (&szlig;-chain of the human chorionic gonadotropin) in the mother's blood serum. The test can be performed between weeks 11+0 and 14+0 of a&hellip;\" class=\"encyclopedia\">first-trimester screening<\/a> leads to an unnecessary invasive intervention with the risk of a miscarriage.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The PPV reflects the rate of positive test results that are confirmed by chromosome analysis or after birth. The risk of the presence of a fetal trisomy 21 during pregnancy is approximately 1:500 for the average population. Almost all of these cases are correctly detected by the Harmony\u00ae test (detection rate 99.3%[1.Stokowski R, Wang E, [&hellip;]<\/p>\n","protected":false},"author":1,"template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"default","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"default","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}}},"class_list":["post-1045","encyclopedia","type-encyclopedia","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.cenata.de\/en\/wp-json\/wp\/v2\/encyclopedia\/1045","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.cenata.de\/en\/wp-json\/wp\/v2\/encyclopedia"}],"about":[{"href":"https:\/\/www.cenata.de\/en\/wp-json\/wp\/v2\/types\/encyclopedia"}],"author":[{"embeddable":true,"href":"https:\/\/www.cenata.de\/en\/wp-json\/wp\/v2\/users\/1"}],"wp:attachment":[{"href":"https:\/\/www.cenata.de\/en\/wp-json\/wp\/v2\/media?parent=1045"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}