Approaches to Genetic Testing: Somatic vs Germline

somatic_germline_1200.jpgNot all genetic tests are created equal. It’s a fact that applies not only to quality, but also to the information that the test reveals. Therefore, it is important to ask: should all genetic tests be assessed the same way? The answer is not a simple “yes” or “no,” but rather the question demands a closer look at the types of variants (changes in the DNA or other biomarkers) the test is assessing. This week, we will highlight the key differences between germline and somatic variants and the implications for tests that examine each.

“Somatic variants are specific to a patient’s tissue; in other words, if you examine a patient’s breast tumor tissue and skin tissue for the same variants, the test results would most likely be different.”

 

Tests that look at somatic variants/changes

Somatic variants are specific to a patient’s tissue; in other words, if you examine a patient’s breast tumor tissue and skin tissue for the same variants, the test results would most likely be different. Tests that look at somatic variants often not only look at DNA but may also look at RNA, methylation patterns (a mechanism used by cells to control gene expression), and protein expression levels. In addition to specificity to the tissue being examined, the variants in the tissue evaluated by these tests may evolve over time, or change with treatment. Somatic variant tests commonly contain words like “biomarker” and “tumor profile.”

genetic questions_1200.jpgQuestions that should be considered in the assessment of tests that look at a somatic variant include:

  • What is the proposed use of the test?
  • When should testing occur (initial biopsy, after treatment)?
  • What biomarkers are being examined?
  • What technologies are being used?
  • What are the methodologies and bioinformatics used to determine results?
  • What will be reported to the requesting medical professional?

“A person’s DNA is typically consistent throughout the cells; thus, if you examine normal tissue from a patient’s breast and normal tissue from a patient’s skin, the test results would be the same.”

 

See an example of our innovation. Click below for a sample Genetic Test Evaluation (GTE) Indication report,

 Sample Indication Report

Tests that look at germline variants

genetic variant_1200.jpgTests that focus on germline variants typically use a patient’s DNA. With minor exceptions, a person’s DNA is consistent throughout the cells; thus, if you examine normal tissue from a patient’s breast and normal tissue from a patient’s skin, the test results would be the same. These germline variants are present at birth and are typically consistent and don’t change over time. What is important to note is that these variants can potentially be passed to offspring, and can thus impact entire families and populations. These tests commonly contain descriptors such as “hereditary,” “familial,” and “screening.”

Questions that should be considered in the assessment of tests that examine germline variant include:

  • Why is the test being requested (diagnostic, decision making, for other family members)?
  • What genes are examined?
  • What methodologies will be used?
  • What will be reported to the requesting medical professional and how will that information be presented?
  • Is the requesting medical professional able to guide and counsel the patient and possibly family members on the results of the test?

 See our blog, Evidence Shines a Light on the Hidden Dangers of Genetic Testing to see why counseling and guidance are important in genetic testing.

genetic science_1200.jpgIt is because of the distinct differences between germline and somatic variants, and thus the tests being used to examine them, that the same assessment tools are not always appropriate. The general scope of each category of test can be challenging to identify, let alone to navigate the intricacies of each particular test. We at Hayes recognize these hurdles and are continuing to evolve our GTE products and services to meet the demands of the genetic testing market. Our innovative solutions provide guidance, education, and support to meet your individual needs around genetic tests.

Click below to download a sample of our GTE Indication, a report about the clinical utility of genetic testing for a specific indication.

 Sample Indication Report

Topics: Hayes Blog, Genetic Testing, Health Technology Assessments,

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