Genetic tests have become increasingly popular and less expensive over the past decade. It only takes a small sample of blood or saliva or a few strands of hair. But your genetic test won't answer all your questions, particularly if you're wondering what is causing issues in your GI tract. Learn when it's appropriate to do a genetic test and when you would be better off testing your gut microbiome to understand what's happening with your health. 

Human genetic tests: what can you learn from a DNA test?

The purpose of a genetic (DNA) test is to identify patterns in your genetic makeup. Your genetic makeup consists of your inherited (germline) and your differentiated (somatic) DNA, both of which are encoded and carried in the chromosomes that make up your cells and organs. Your entire DNA, both germline and somatic, reflects your health, vitality, and optimal function of every part of your body by regulating the expression of genes and proteins. A genetic test can check for changes in the chromosomes, genes, or proteins, and it can identify genetic conditions or the chance of developing or passing on a genetic disorder to your kids. 

Genetic tests are most often used in clinics to screen for possible congenital abnormalities, newborn/neonatal disorders, inherited disorders, pre-symptomatic testing for adult-onset and complex disorders, and how one may respond to a pharmaceutical. Commercially, genetic testing is being used by many for personal information and educational purposes, like genetic ancestry (i.e., genealogy or family history) or wellness status (e.g., reports on disease carriers, food sensitivities, athletic potential, etc.).

Genetic test options

Genetic tests can be performed either in a clinical setting, like a hospital or doctor's office, or at home. Depending on the genetic analysis, a shorter or a longer piece of your DNA may be required, and, in the case of a test that involves whole genome sequencing, your entire DNA needs to be sequenced, read, and analyzed. 

To understand the scalability of the various genetic tests, you can consider that a single change in the sequence of your DNA involves a single change in one base, a single gene contains approximately 3,000 bases, genetic loci have 30,000 to 3 million bases, a chromosome has 100 million bases, and our entire DNA consists of 3 billion bases. 

You can also think of your DNA sequence as a book that tells your story with significant words, sentences, and paragraphs. What's important to realize is that not every word, sentence, or paragraph is significant. Genetic tests are designed to determine what is significant and insignificant--  in a case by case example. One letter is like a base. Many letters (bases) make up a word (genes). Words (genes) are put together to make sentences (chromosomes), but the sentences (chromosomes) contain both significant and insignificant words creating your entire book, your entire story, your entire DNA. Some genetic tests read genes and loci (i.e., areas with meaningful or unmeaningful information) that involve a few specific bases. In contrast, other tests require reading and analyzing the entire human DNA story.

The data that comes from analyzing the entire human DNA is considered BIG data.

Here are the most common options of genetic tests and what you can learn from each:

  • Molecular genetic test or gene test: This test utilizes a sample of blood, saliva, hair, skin, amniotic fluid (the fluid that surrounds a baby during pregnancy), or other tissue. The molecular genetic or gene test examines short lengths of DNA or regions of genes to identify variations or mutations (single- or many- base DNA changes) that are clinically linked to genetic disorders.1
  • Chromosomal genetic test or karyotyping: This test typically uses samples of blood, amniotic fluid, bone marrow, or other tissue and analyzes chromosomes or longer lengths of DNA. This test aims to help diagnose genetic diseases, possible congenital disabilities, and certain disorders of the blood and the lymphatic systems.2
  • Biochemical genetic test: This test studies the amount or the activity of specific enzymes or proteins. Possible unusual quantity or activity of a specific protein can indicate changes to the DNA that result in a genetic disorder. The biochemical genetic test can be performed from a blood or urine sample, spinal or amniotic fluid, or other tissue.3
  • Whole-exome and whole-genome sequencing: These two methods are increasingly used in healthcare and research to identify genetic variations. They rely on new technologies that allow rapid sequencing of large amounts of DNA. These new technologies are known as next-generation sequencing.
    • Exome sequencing involves reading all exons, the pieces of your DNA that provide instructions for making proteins (or all meaningful information, if you consider the example of the book), which is only about one percent of your entire genome. Because research has identified DNA variations outside the exons that affect genes and proteins and lead to genetic disorders, exome sequencing will not be sufficient to capture the DNA variations that happen outside the exons. In this case, whole-genome sequencing that reads the whole DNA genome in its entirety can determine all variations in any part of the genome, and it is the most powerful and informative genetic test.4

Microbiome tests: How are microbiome tests different than genetic tests?

A microbiome test is designed to examine the community (both the quantity and composition) of commensal, symbiotic, and pathogenic microorganisms that inhabit the human body. Microbial communities in and on the human body that are being microbiome tested commonly include the digestive tract (gut), skin, mouth, nose, and vagina. In these locations, the human microbiome contains bacteria, fungi, archaea, viruses – and their genetic components. Unlike a genetic test, a microbiome test (no matter the area tested) can detect and measure human DNA—but the primary analysis is of those microorganisms!

In 2008, researchers pioneered the Human Microbiome Project to understand the impact that all living microorganisms within the human body may have on health and disease.5 These microorganisms, which consist of 10-100 trillion cells and comprise more than 10,0000 species, are generally not harmful but beneficial and often are even essential to our health and wellbeing.6 

The analysis of a microbial community is also considered BIG data.

To understand the volume and significance of this microbial community, consider this example: the bacteria in an average human body comprise are 10x more prevalent than cells in the human body; furthermore, they encode about 1,000 more genes compared to the human genome. However, because of their small size, bacteria and other microorganisms make up only about 1-3 percent of our body mass. It translates to 2-6 pounds of bacteria in a 200-pound adult, which is still significant.

What can a microbiome test tell you?

In comparison to a genetic test, a microbiome test measures the composition and activity of either a sup-population (part of the microbial DNA) or the entire population of the microorganisms (whole microbial DNA) in particular locations. Research has demonstrated the levels and activity of specific microbes in our bodies play essential roles in our health or disease status. 

For example, individuals who suffer from intestinal conditions, such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD), present with specific bacterial imbalances and have a much smaller diversity in their gut microbiome than healthy controls.7 Similarly, research has shown skin microbiota depends on a person's age, sex, and environment (i.e., temperature and humidity, antibiotic treatment, cosmetics, soaps, and hygienic product usage).8

The most common commercial microbiome tests are designed to assess the gut microbiome and its types, amounts, and activity of the microorganisms that inhabit the digestive tract. A gut microbiome test requires a small stool sample to be sent to a laboratory for microscopic, chemical, and/or microbiological testing. 

Thorne’s Gut Health test is not intended to diagnose, treat, cure, or prevent diseases; you should always consult a qualified health-care professional.

Commercial gut microbiome test options 

The following gut microbiome tests are offered as direct-to-consumer tests and can be collected at home. What you can learn from the test depends on the sequencing technology of the sample:

1. 16S sequencing-based DNA gut microbiome test: 

  • Pros: You may gain basic insights into bacteria present that can cause infections or dysbiosis in your gut flora. 
  • Cons: This sequencing reads a particular gene among bacterial populations. It provides a view of only the known bacterial species and some of their functional capabilities.

2. Next-generation RNA gut microbiome test (metatranscriptomic test): Analyzes the RNA of your gut microbes, a piece of DNA that has the potential to turn into protein and reflects the microbial activity and metabolism in your gut. 

  • Pros: It is a high-resolution test and can detect live microorganisms and examine their function. 
  • Cons: It tends to lose viability and resolution compared to DNA sequencing because RNA is more unstable than DNA. It provides information only on elements of the DNA that get converted to RNA.

3. Next-generation shotgun-based DNA gut microbiome test (metagenomic test): This sequencing examines the entire DNA of all gut microbes. Like the whole-genome genetic tests, the shotgun-based DNA microbiome test reads the whole DNA of gut microorganisms and is not limited to specific or known regions (like RNA testing). 

  • Pros: This technology provides more detailed information and at a much higher resolution level. This option:
    • Identifies the entire bacterial population down to the strain level
    • Identifies viruses, archaea, and fungi, as well as their metabolic activity and functionality 
    • Examines unknown populations within your gut community that are unique to you and may be responsible for conditions or problematic symptoms
    • Analyzes microbial activity and metabolic potential via functional pathway analysis and other advanced computational methods 
  • Cons: Since the sequencing is so in-depth, results can take about three weeks.

While we do not currently offer a human genetic test, Thorne’s Gut Health Test uses next-generation metagenomic (DNA) sequencing and will answer what is going on in your GI tract. It can provide an accurate, complete, and detailed microorganism breakdown, information about your risk for inflammation, gut probiotic levels, gut diversity, and metabolic potential to produce micronutrients. The Gut Health test considers relevant information from your health profile, such as your current symptoms, diagnoses, medications, and nutritional intake, when designing your insights and recommendations. With the power of Thorne Health Intelligence, your Gut Health report recommends personalized solutions (diet, prebiotics, probiotics, foundational nutrients) to rebalance your gut and support health goals.  

References

  1. Katsanis SH, Katsanis N. Molecular genetic testing and the future of clinical genomics. Nat Rev Genet. 2013;14(6):415-426. doi:10.1038/nrg3493
  2. Dugoff L, Norton ME, Kuller JA. The use of chromosomal microarray for prenatal diagnosis. Am J Obstet Gynecol. 2016;215(4):B2-B9. doi:10.1016/j.ajog.2016.07.016
  3. Mayo Clinic on genetic testing. https://www.mayoclinic.org/tests-procedures/genetic-testing/about/pac-20384827.
  4. NIH on DNA sequencing. https://ghr.nlm.nih.gov/primer/testing/sequencing.
  5. Turnbaugh PJ, Ley RE, Hamady M,et al. The Human Microbiome Project. Nature. 2007. doi:10.1038/nature06244
  6. Ursell LK, Metcalf JL, Parfrey LW, Knight R. Defining the human microbiome. Nutr Rev. 2012;70(SUPPL. 1):S38. doi:10.1111/j.1753-4887.2012.00493.x
  7. Presti A Lo, Zorzi F, Chierico F Del, et al. Fecal and mucosal microbiota profiling in irritable bowel syndrome and inflammatory bowel disease. Front Microbiol. 2019;10(JULY). doi:10.3389/fmicb.2019.01655
  8. Grice EA, Segre JA. The skin microbiome. Nat Rev Microbiol. 2011;9(4):244-253. doi:10.1038/nrmicro2537