Molecular testing, or molecular diagnostics, refers to a group of tests that look at the genetic material in a specimen. It can detect genetic risk factors for certain diseases or provide evidence of infections in the body.
Molecular tests use many different techniques to detect and amplify the visibility of molecules in samples. Samples may come from saliva, blood, or a biopsy.
In many contexts, molecular testing offers greater precision. For example, doctors may use it to determine the specific genetics of a type of cancer, thereby enabling them to target treatment better.
Read on to learn more about molecular testing.
It is very accurate when performed correctly. In some cases, molecular testing may offer certainty after a person gets a tentative diagnosis.
Several techniques can detect the presence of the targeted genetic material in a cell, and each technique works slightly differently. Examples of some techniques include:
- fluorescent in situ hybridization (FISH)
- chromosomal microarray analysis
- cytogenetic analysis or karyotyping
With each technique, doctors collect a sample from the body and then process the sample in a slightly different way to make the molecules more visible. Then, a technician looks at the sample under a microscope and provides a report.
Doctors use molecular testing to get more diagnostic information and to predict outcomes for patients. These tests serve many purposes, including:
- assessing the risk of various diseases
- confirming the presence of specific infections that defy traditional laboratory techniques
- helping counsel people who are pregnant or plan to become pregnant
- helping in making treatment decisions
- assessing how well a person might respond to medication
- diagnosing certain diseases, or subtypes, such as breast cancer
Each test requires a material sample from an individual. For example, COVID-19 tests look for specific viral antigens in nasal and respiratory secretions. Antigens are typically found on the surface of viruses.
- a tumor via a biopsy
- bodily fluids, such as respiratory secretions
- amniotic fluid
Molecular testing is evolving rapidly, with an increasing number of tests available. For example,
In general, molecular testing falls into two broad categories with many different subtypes. These include:
Genome sequencing and testing
Genome sequencing can also assess whether a person carries a gene for a disease. This is a common type of testing when a person is pregnant or planning to become pregnant.
Another use of genome sequencing is to
This type of testing offers many benefits, including:
- Preconception assistance: If a person carries the gene for certain harmful or potentially fatal illnesses, this may affect their family planning decisions.
- Health decision-making: A person who has a higher risk of certain diseases may make long-term plans based on this knowledge or change their lifestyle to reduce their risk. Testing for various cancer-related genetic variants may guide breast cancer screening.
- Other uses: Some people pursue molecular home testing to learn about potential ancestry or because they are curious about their genetic inheritance.
There are also some drawbacks:
- Reliability: The reliability of testing can vary, especially when a person uses home genetic tests. Tests identifying genetic risk factors do not guarantee that a person will develop a disease and may needlessly cause anxiety.
- Decision-making: Making decisions based on genetic information can be challenging. For example, a person may have to decide whether to terminate a pregnancy if they learn that there is a 50% chance their child will carry a fatal disease.
- Accessibility: Molecular testing is not accessible to everyone. It can be expensive and may not be covered by insurance.
- Privacy: Using private companies for non-medical genetic testing may compromise a person’s genetic privacy.
Another type of genetic testing involves looking for genetic markers of infections or diseases. Rather than sequencing a person’s genome, these tests examine specimens for the presence of embedded genetic signals that strongly correlate with the suspected disease.
COVID-19 PCR testing
Oncologists may also perform genetic testing on certain types of cancer tumors. Different genetic signatures may provide information about the type of cancer a person has, as well as which treatment is most likely to be effective.
The major benefit of genetic marker testing is that it tends to be highly accurate. In some cases, these tests can confirm a diagnosis. Also, it can help people and experts make well-informed medical decisions or guide treatment better.
The drawbacks of these tests include:
- Accessibility: Molecular testing is often more expensive and may be less accessible. For example, COVID-19 molecular tests take several days to get a result, while home antigen tests take less time. Additionally, not all people are eligible for all molecular tests.
- Reliability: Molecular testing for diseases and infections is generally accurate, but no test offers 100% reliability.
- Issues with samples: The samples obtained may be insufficient for testing and hinder the process, such as when a biopsy does not yield enough tissue.
Polymerase chain reaction (PCR) tests are a type of molecular test that can detect COVID-19. They work by searching for the diagnostic
These types of tests typically take several days to get a result back.
What is the difference between antigen and molecular tests for COVID-19?
Antigen tests look for viral proteins. These proteins are easier to detect, and tests may produce a rapid positive or negative result.
PCR tests look for viral genetic material and then multiply it so the diagnostic technology can confirm the presence of the virus. This type of test is more sensitive and complex — it can detect the virus before someone becomes symptomatic or infectious.
Below are some common questions and answers about molecular testing:
How can molecular testing help with cancer treatment?
Molecular testing can help guide treatment for some people with cancer. However, molecular testing might not be useful in all situations, such as
- a biopsy of the tissue cannot be taken
- a biopsy sample is not adequate
- tests provide limited details
Sometimes, even if molecular testing directs you to a certain treatment type, there is no guarantee that it will treat cancer effectively.
What is next-generation sequencing?
Also, next-generation sequencing can detect smaller genetic variations, offering a more comprehensive view of a person’s genome and genetic risk factors.
How accurate is molecular testing?
The accuracy of molecular testing depends on the test. Overall, the accuracy is good but not perfect.
For example, a
- The summary sensitivity of the tests was 95.9%, meaning very few false-negative results.
- The summary specificity was 97.2%, meaning very few false-positive results.
- Some tests were less accurate, with an overall sensitivity range of 80.5% to 96.6%.
A lab often determines the accuracy of a test by measuring sensitivity and specificity. High levels of both these measures means the test can correctly identify people with and without a specific disease.
Molecular testing is a type of genetic testing that offers significant insight into a person’s genome. It can also detect signs of certain infections and diseases based on those conditions’ unique genetics.
It is rapidly evolving, with more options for molecular testing becoming available.
Genetic sequencing is improving with next-generation sequencing techniques. However, it is important for people to understand the limitations of molecular testing. This is especially true with types of genetic testing that do not offer certainty, such as prenatal testing.