DNA Test vs ctDNA Test: The Differences in Modern Diagnostics

In the rapidly evolving landscape of medical diagnostics, genetic testing has become a cornerstone of personalised healthcare. Among the most discussed innovations are DNA testing and circulating tumour DNA (ctDNA) testing—two powerful tools that serve distinct purposes in clinical practice. While both involve analysing genetic material, their applications, methodologies, and implications differ significantly.

This blog explores the key differences between DNA and ctDNA testing, their roles in healthcare, and how they are shaping the future of precision medicine.

DNA Testing: The Blueprint of Inherited Risk

DNA testing (or genetic testing) refers to the analysis of an individual's germline DNA, which is inherited from their parents and remains largely unchanged throughout life. Approximately 5 to 10% of cancers are caused by inherited genetic changes. DNA testing is commonly used to:

Confirm or exclude the presence of a genetic disease

Assess genetic predisposition to diseases such as breast cancer, colorectal cancer, Huntington’s disease, or cystic fibrosis

Identify carrier status for inherited conditions

Guide pharmacogenomic decisions

Samples for DNA testing are typically collected via saliva, blood, or buccal (inner cheek) swabs. The results provide a static snapshot of a person’s genetic makeup, offering insights into potential health risks but not necessarily current disease status.

For example, a BRCA1 mutation identified through DNA testing suggests a higher lifetime risk of breast cancer and ovarian cancer, but it does not confirm the presence of cancer at the time of testing.

Types of DNA tests

Genetic testing examines your genes or chromosomes, which is composed of DNA. Below are some examples:

Gene testing

Genomic testing

Chromosome testing

Gene expression testing

ctDNA Testing: A Real-Time Window into Cancer

Circulating tumor DNA (ctDNA) testing is a form of liquid biopsy that analyses fragments of DNA shed by tumor cells into the bloodstream. Unlike germline DNA, ctDNA reflects somatic mutations—genetic changes acquired during a person’s life, often due to cancer.

ctDNA liquid biopsy has emerged as a minimally invasive method for:

Early cancer detection and screening

Molecular profiling and targeted therapy selection

Monitoring treatment response

Assessing minimal residual disease (MRD) and disease relapse

Detecting resistance mutations

Because ctDNA has a short half-life—less than 2 hours in the circulation—it provides a near real-time snapshot of disease activity. This dynamic quality makes ctDNA especially valuable in oncology, where timely insights can guide treatment decisions and improve outcomes.

OT&P offers Lucence INSIGHT™ Liquid Biopsy Cancer Screening Service, contact us for more information.

Comparing DNA and ctDNA Testing: Key Differences

	DNA Testing	ctDNA Testing
Source	Germline DNA	Tumor-derived DNA
Purpose(s)	Risk assessment	Early cancer detection Disease monitoring
Sample Type	Saliva, blood, buccal swab	Blood (liquid biopsy)
Timing	Static	Dynamic, real-time
Use Case	Inherited conditions	Cancer diagnostics

Which test suits me better?

While DNA testing is insightful for preventive medicine, ctDNA testing is revolutionising real-time cancer care. The two are complementary, not competitive—each serving a unique role in the continuum of care.

Below is a general guide to help determine who may benefit most from DNA testing or ctDNA liquid biopsy:

DNA testing for inherited cancer risk

Cancer patients

Blood relatives of a cancer patient

Anyone interested in assessing the risk of hereditary cancer

CtDNA liquid Biopsy

Individuals aged 40 years or older

Individuals with family history of cancer
Anyone interested in early cancer detection

Consult our GP to determine which testing option is most suitable for you.

A Dual Lens on Health

DNA and ctDNA testing offer two distinct but complementary lenses into human health. DNA testing provides a foundational understanding of inherited risk, while ctDNA testing offers a dynamic view of disease in action—especially in oncology.

Together, they empower clinicians and patients to make more informed, personalised decisions. As accessibility improves and technologies evolve, these tools will play an increasingly central role in precision medicine.

If you’re unsure which option best aligns with your medical profile, consult our GPs at OT&P for personalised advice.