{"id":1642,"date":"2016-10-07T12:42:27","date_gmt":"2016-10-07T12:42:27","guid":{"rendered":"https:\/\/www.lalpathlabs.com\/blog\/?p=1642"},"modified":"2023-10-12T10:41:09","modified_gmt":"2023-10-12T05:11:09","slug":"microarray-testing","status":"publish","type":"post","link":"https:\/\/www.lalpathlabs.com\/blog\/microarray-testing\/","title":{"rendered":"Advanced Cytogenetic Technique – Microarray Testing"},"content":{"rendered":"

\"microarray<\/p>\n

Advanced Cytogenetic Technique:\u00a0<\/span>Microarray Testing<\/span><\/h2>\n

\"prenatal\"<\/p>\n

\u2022 20% of stillborn babies have a major malformation
\n\u2022 3% of live-births have congenital anomalies
\n\u2022 Diagnosis of a malformation requires:
\n– A number of \u201cbroad spectrum\u201d analysis
\n– Followed by more sophisticated, accurate and targeted tests
\n\u2022 Detailed ultrasound and invasive fetal testing
\n– Etiology
\n– Prognosis
\n– Recurrence risk
\n– Prevention \/ options in future pregnancies<\/p>\n

\"classical\"<\/p>\n

\"comparison\"<\/p>\n

\"genomic\"<\/span><\/strong><\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

Genomic microarray technology<\/span><\/strong><\/p>\n

Each microarray contains 2.6 million markers for copy
\nnumber & 750,000 SNPs markers
\nYield is 15-20%<\/strong>
\nWhole genome- High resolution<\/strong><\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

\"microarray\"<\/p>\n

ACMG Recommends Replacing Karyotyping with Chromosomal Microarrays as<\/span><\/strong>
\n\u2018First-Line\u2019 Postnatal Test<\/span><\/strong><\/p>\n

“Increased resolution of microarray technology over conventional cytogenetic
\nanalysis allows for identification of chromosomal imbalances with greater
\nprecision, accuracy and technical sensitivity.\u201d<\/p>\n

\"chromosomal\"<\/p>\n

\"affymetrix\"<\/p>\n

Affymetrix-25 mers are in-situ synthesized on a glass<\/span>
\nwafer nucleotide by nucleotide using photolithography<\/span><\/p>\n

\"affy\"<\/p>\n

\"indications\"<\/p>\n

\"indications<\/p>\n

\u2022 Advanced maternal age<\/p>\n

\u2022 Previous child with de novo chromosome aneuploidy<\/p>\n

– Woman 30 years, child with T21: Increased Recurrence risk for any
\nchromosome abnormality (1\/100) versus age-related risk (1\/390)<\/p>\n

\u2022 Parental structural chromosome abnormality<\/p>\n

\u2022 Family history of genetic disorder<\/p>\n

\u2022 Elevated risk based on maternal screening<\/p>\n

\u2022 Foetuses with abnormal ultrasound findings<\/p>\n

\"recommendations\"<\/p>\n

Based on the increased detection of clinically relevant abnormalities in both structurally normal\u00a0and abnormal pregnancies, Chromosomal Microarray Analysis (CMA) should be transitioned to\u00a0become the First Tier Test for invasive prenatal diagnosis.<\/p>\n

Source: New England Journal of medicine,Vol 367,No 23,Dec.2012<\/p>\n

\"conclusion\"<\/p>\n

\u2022 CMA detects chromosome abnormalities and new genetic syndromes which would be\u00a0missed by conventional cytogenetics<\/p>\n

\u2022 Most Copy Number Variations can be interpreted based on gene content, size, inheritance,\u00a0databases<\/p>\n

\u2022 Counseling issues are not unique to prenatal CMA<\/p>\n

\u2022 As CMA transitions into clinical practice counseling by professional with knowledge and\u00a0expertise in CMA will be required<\/p>\n

\u2022 Need large databases of array findings and associated phenotype from\u00a0\u201cunbiased populations\u201d<\/p>\n

\"acog<\/p>\n

\u2022 If a fetal structural anomaly is identified on ultrasound examination, invasive prenatal diagnosis\u00a0should be offered<\/p>\n

\u2022 A negative cell free fetal DNA test<\/a><\/span> result does not ensure an unaffected pregnancy<\/p>\n

\u2022 A patient with a positive test result should be referred for genetic counseling and offered\u00a0invasive prenatal diagnosis for confirmation of test results<\/p>\n

\u2022 Cell free fetal DNA does not replace the accuracy and diagnostic precision of prenatal diagnosis\u00a0with CVS or amniocentesis, which remain an option for women<\/p>\n

\"pre-natal\"<\/p>\n

1.<\/strong> In patients with a fetus with one or more major structural abnormalities identified by ultrasound\u00a0who are undergoing invasive prenatal diagnosis, Chromosomal Microarray Analysis is
\nrecommended. This replaces traditional fetal karyotype \u2013 which may be viewed as a\u00a0low-resolution whole genome analysis.<\/p>\n

2.<\/strong> In patients with a structurally normal fetus undergoing invasive prenatal diagnostic testing<\/a><\/span>,\u00a0either traditional chromosome analysis or chromosome microarray analysis may be performed.<\/p>\n

3.<\/strong> As most copy number mutations identified by Chromosomal Microarray Analysis are not\u00a0associated with increasing maternal age, the use of CMA for prenatal diagnosis should not be
\nrestricted to women aged 35 and older.<\/p>\n

4.<\/strong> In case of intrauterine fetal demise or stillbirth, when further cytogenetic analysis is desired,\u00a0Chromosomal Microarray Analysis on fetal tissue is recommended. This increases the likelihood
\nof obtaining results and improves the detection of causative abnormalities.<\/p>\n

\"poc<\/p>\n

\u2022<\/span> Approximately 60-70% of first trimester miscarriages are being caused by chromosomal\u00a0abnormalities
\n\u2022<\/span> Traditional cytogenetic analysis<\/a><\/span> of these samples is challenging due to high rates of culture\u00a0failure and maternal contamination
\n\u2022<\/span> Chromosomal microarray analysis overcomes these limitations and has proven to be an\u00a0excellent tool for detection of chromosomal aberrations in these samples<\/p>\n

Ref. : Wang et al.Molecular cytogenetics 2014 7:33<\/span><\/p>\n

\"tests\"<\/p>\n

\"availabe\"<\/p>\n

Download PDF<\/strong><\/a><\/p>\n