Skip to Main Content

Molecular Diagnostics

  • A test that sequences a patient's DNA or RNA for markers of potential future diseases
  • Areas of molecular diagnostics include infectious diseases, hematopathology, genetics, solid tumor
  • Tests can be done to see if someone will be resistant to a specific drug
  • Involves laboratory medicine

Molecular Diagnostics


You have likely heard about mail-order genetic DNA testing kits. By providing a saliva sample you can receive a DNA analysis of the particular code in your cells that makes you unique. This consumer-facing diagnostic test, referred to by one startup as a genetic "service," has taken the world by storm in recent years. 

But John Howe, PhD, director of the molecular diagnostics laboratory at Yale School of Medicine, explains that these at-home kits cannot provide the level of detail and information that patients receive from a place like the Yale Center for Genomic Analysis. 

What is molecular diagnostics?

Molecular diagnostics, also called molecular pathology, involves taking DNA or RNA, the unique genetic code found in our cells, and analyzing the sequences for red flags that can pinpoint the potential emergence of a specific disease. The field has expanded rapidly in recent years. 

"When I came to the laboratory medicine department in 1992, there were just a few molecular diagnostic tests," Howe says. "But now there are molecular tests in most of the areas of pathology."

The four areas of molecular diagnostics at Yale Medicine include: 

  • Infectious diseases (including microbiology and virology)
  • Hematopathology 
  • Genetics 
  • Solid tumor 

What are examples of common molecular diagnostics tests?

Tests are typically performed to determine whether or not patients have a gene mutation associated with a specific disease, either as an inherited or an acquired mutation. Inherited diseases can be tested for at the prenatal, newborn and adult stages of life. 

For example, a commonly inherited disease is cystic fibrosis (CF). If a newborn is found to have two mutations in the gene associated with CF, the baby is most likely to have the condition. The child can then be treated for the disease, which can prolong his or her life. 

Doctors can perform a molecular test of a common inherited hereditary cancer. For example, in breast cancer, they can investigate for specific inherited mutations in the BRCA1 and BRCA2 genes, which may increase the patient's risk of breast and ovarian cancer.

Acquired gene mutations can be tested for in some cases, such as for chronic myeloid leukemia (CML). A patient can then start therapy as soon as possible. 

Tests can also be done to determine whether a person has become resistant to a specific drug and needs to change course in a treatment regimen. For example, an HIV patient can be monitored by a quantitative molecular test to determine whether or not the amount of viral load has significantly increased, which is a sign of resistance to the treatment. The patient’s HIV can then be DNA sequenced to determine if a mutation known to be associated with resistance is found.

Why is next-generation sequencing an important scientific advancement?

Genome sequencing refers to understanding the order of the approximately 3 billion DNA bases (nucleotides) in a genome that make up a person’s complete DNA. “Following the first genetic sequencing of the human genome, there was an explosion in DNA sequencing innovation, which spawned the development of next-generation sequencing," Howe says. "This has allowed DNA sequencing to be performed more efficiently and therefore has created lots of testing opportunities." 

Next-generation sequencing, also referred to as massively parallel sequencing, is a term used to describe modern sequencing technologies. Next-generation sequencing uses a single format where a wide range of biological phenomena can be tested, such as, mRNA expression and methylation status.

What's next for the field of molecular diagnostics?

"We are at the beginning stages of understanding what those changes to the DNA sequence that indicate disease mean and why they occurred,” Howe says. “We have all this additional information, and now we need to figure out what to do with it – how to best use and apply this new knowledge.” 

Research scientists are using this vast new amount of information to try and focus more deeply on understanding various diseases. "The more we truly understand about diseases, the more refined a diagnosis and treatment can become,” Howe says. 

What makes Yale Medicine's approach to molecular diagnostics unique?

“We have clinicians – both pathologists and oncologists – who want our department to remain at the forefront of new developments in molecular diagnostics testing, so that they can make available more therapeutic options to their patients,” Howe says. "This is what actually led the lab to develop tumor gene panels using next-generation sequencing."

"We are constantly striving to make our testing more extensive and cutting-edge at Yale Medicine," Howe says.