DNA

Test indications include suspected genetic disorders in children and adults for whom a targeted genetic testing approach is likely to be low yield or has already failed.

Analytic validity, diagnostic yield and clinical utility are similar or superior to other clinical genetic tests, such as exome sequencing, chromosomal microarray analysis and next-generation sequencing gene panel tests.

Appropriate adoption of genome sequencing as a molecular diagnostic test in Canada would be facilitated by a cohesive national strategy for genomic medicine.

Genetic testing of patient constitutional DNA (i.e., their genome) is increasingly performed in medical practice. 1–3 Sequencing an entire human genome (about 3.2 billion nucleotides) is now possible to complete in days to weeks, and at a similar cost to some advanced imaging tests or to a brief admission to hospital.3,4 Genome sequencing is being integrated into health care systems internationally, most notably in the United Kingdom.5 Starting in 2021, genome sequencing is being performed as a clinical genetic test in Ontario, Canada.

Author/s:

Costain, G., Cohn, R. D., Scherer, S. W., Marshall, C. R.

Screening for Colon Cancer in Older Adults: Risks, Benefits, and When to Stop

Brian Desmarais — Fri, 03 Jan 2020 19:11:46 +0000

Date Added:

January 3, 2020

Journal/Publication:

The Mayo Clinic Proceedings

Publication Date:

January 1, 2020

Issue:

Volume:

Pages:

184–196

URL:

Screening for Colon Cancer in Older Adults: Risks, Benefits, and When to Stop

Type:

Meta-analyses, Reviews, and Guidelines

Format:

Article

DOI (1):

https://doi.org/10.1016/j.mayocp.2019.02.021

Keywords

MeSH

A fair and balanced review of CRC screening in older people from Mayo. James W. Mold, MD, MPH

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Colorectal cancer (CRC) is the fourth leading cause of cancer and second leading cause of mortality from cancer in the United States. As the population ages, decisions regarding the initiation and cessation of screening and surveillance for CRC are of increasing importance. In elderly patients, the risks of CRC and the presenting signs and symptoms are similar to those in younger patients. Screening and ongoing surveillance should be considered in patients who have a life expectancy of 10 years or more. Life expectancy estimates can be calculated using online calculators. If screening is deemed appropriate, the choice of which test to use first is unclear. Currently, there are a number of modalities available to screen for CRC, including both invasive modalities (eg, colonoscopy, sigmoidoscopy, capsule colonoscopy, and computed tomographic colonography) and noninvasive modalities (fecal immunochemical test, stool DNA testing, and blood testing). Colonoscopy and other invasive testing options are considered safe, but the risks of complications of the bowel preparation, the procedure, and sedation medications are all increased in older patients. In contrast, noninvasive testing provides a safe initial test; however, it is important to consider the increased false-positive rates in the elderly, and a positive test result will usually necessitate colonoscopy to establish the diagnosis. Ongoing screening and surveillance should be a shared decision-making process with the patient based on multiple factors including the patient’s morbidity and mortality risk from CRC and his or her underlying comorbidities, the patient’s functional status, and the patient’s preferences for screening. Ultimately, the decision to initiate or discontinue screening for CRC in older patients should be done based on a case-by-case individualized discussion.

Author/s:

Nee, J., Chippendale, R. Z., Feuerstein, J.D.

Consistency of Direct to Consumer Genetic Testing Results Among Identical Twins

Brian Desmarais — Wed, 19 Jun 2019 00:34:45 +0000

Date Added:

June 18, 2019

Journal/Publication:

The American Journal of Medicine

Publication Date:

June 15, 2019

URL:

Consistency of Direct to Consumer Genetic Testing Results Among Identical Twins

Type:

Clinical Research Results

Format:

Article

DOI (1):

10.1016/j.amjmed.2019.04.052

Keywords

MeSH

Direct-To-Consumer Screening and Testing

This study calls into question the accuracy of direct-to-consumer genetic testing. James W. Mold, MD, MPH

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Abstract

Purpose

To evaluate the consistency of 3 commonly used direct to consumer genetic testing kits.

Background

Genetic testing kits are widely marketed by several companies but the consistency of their results is unclear. Since identical twins share the same DNA, their genetic testing results should provide insight into test consistency.

Methods

42 identical twins (21 pairs) provided samples for three testing companies. Outcomes were concordance of ancestry results when i) twin pairs were tested by the same company and ii) the same participant was tested by different companies. Concordance of 8 self-reported traits with 23andMe genetic analyses were also examined.

Results

Concordance of ancestry results when twin pairs were tested by the same company was high, with mean percent agreement ranging from 94.5%–99.2%. Concordance of ancestry results when participants were tested by two different companies was lower, with mean percent agreement ranging from 52.7%–84.1%. Concordance of trait results was variable, ranging from 34.1% for deep sleep and detached earlobes to 90.2% for cleft chin.

Conclusion

The consistency of consumer genetic testing is high for ancestry results within companies but lower and more variable for ancestry results across companies and for specific traits. These results raise questions about the usefulness of such testing.

Author/s:

Huml, A.M., Sullivan C., Figueroa, M., Scott, K., Sehgal, A.R.

What Are Polygenic Scores and Why Are They Important?

Tracy Ashby — Tue, 09 Apr 2019 05:00:00 +0000

Date Added:

April 9, 2019

Journal/Publication:

JAMA

Publisher:

American Medical Association

Publication Date:

April 8, 2019

Format:

Article

DOI (1):

10.1001/jama.2019.3893

Keywords

PMID (1):

30958510

MeSH

eye color

multifactorial inheritance

genomics

DNA

risk factors

cardiovascular diseases

Polygenic prediction scores are the next thing to watch for in the genomics arena. It is probably worth reading about them now. This is a concise 1 ½-page summary. James W. Mold, MD, MPH

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Mendelian disorders and monogenic traits result from combinations of variants in 1 or a few genes that have a large effect on the propensity for developing a certain disease or characteristic. In contrast, complex traits, such as eye color or cardiovascular disease, are determined by variations occurring in many genes that have smaller effect sizes and act over long periods of time, often in concert with environmental factors. The cumulative risk derived from aggregating contributions of the many DNA variants associated with a complex trait or disease is referred to as a polygenic risk score (also known as a genetic risk score). This JAMA Genomics and Precision Health article explains polygenic risk scores as determinants of an individual’s inherited risk for complex disease.

Author/s:

Sugrue, Leo P., Desikan, Rahul S.

Cautions Regarding Over-The-Counter Genetic Tests

Jeffrey Wilson — Sun, 24 Feb 2019 19:45:16 +0000

Date Added:

February 24, 2019

Publication Date:

February 21, 2019

Type:

Patient Education Materials

Format:

Article

Keywords

DNA Tests

Genetic testing

MeSH

DNA

Information for patients about risks involved in getting over-the-counter proprietary DNA testing.

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Over-the-Counter DNA tests are now easy and affordable. They can be informative and fun. However, there are certain risks involved.

Author/s:

Mold, James