Researchers have come up with a low-cost DNA test that can detect cervical cancer within 45 minutes.
Cervical cancer is the fourth most common type of cancer among women, with an estimated 604,127 cases worldwide. At least 341,831 people have succumbed to the disease in 2020, an international study noted. The same study said 21% of the cases were reported from India.
What causes cervical cancer?
The primary cause of cervical cancer is an infection caused by a virus called the human papillomavirus (HPV). It causes warts on or around the genitals. Though not all strains of the virus are cancerous, 14 strains are categorised as high-risk. Of these, HPV16 and HPV18 are responsible for almost 70% of HPV-related cervical cancer cases across the world.
In high-income countries, interventions such as vaccines and screening tests have brought down the number of HPV-related cancer cases. However, low- middle-income countries such as sub-Saharan countries have not been able to establish adequate screening and vaccination programmes that can address the health risk.
Explainer | How is India trying to beat cervical cancer?
Part of the reason for poor facilities is that the screening tests used in these regions are expensive and require complex laboratory equipment and trained technical staff.
The procedure used for the tests also takes a lot of time to deliver results as the equipment can only be run when there is an adequate number of samples. This can delay test results by days, or even weeks, which can cost patients a lot of time, especially in poor countries where patients may need to travel long distances to get results.
To this end, scientists have developed a low-cost, easily manufactured test that can give results almost as accurately as the standard test used while cutting short the wait time to 45 mins.
How does the test work?
The standard test, called digene Hybrid Capture 2 test, uses DNA of the virus to detect its presence.
“The digene HPV DNA test uses the principle of hybrid capture,” Rebecca Richards-Kortum, a bioengineer and one of the co-authors of the new study, told The Hindu in an email.
The test includes complementary sequences of high-risk HPV RNA that bind with the HPV DNA in the sample to create RNA-DNA hybrids. Antibodies are used to capture any RNA-DNA hybrids which are detected via chemiluminescence (emission of light due to a chemical reaction).
“Due to the complexity of the method, the test requires a substantial amount of equipment, including a plate reader,” Dr. Richards-Kortum said.
The new test uses a method called isothermal DNA amplification: instead of using heat to separate the double-stranded DNA, a type of enzyme called DNA polymerase is used. These enzymes can directly displace the double strands of the DNA as they synthesise a complementary strand.
Once the DNA strands are amplified, scientists can test the strands for HPV virus.
Also Read | Understanding the HPV vaccine’s risk
“Amplification can occur rapidly, in as little as 10 minutes in some cases,” Dr Richards-Kortum added.
How are the test administered?
The test used two kinds of samples: the first batch was collected from the U.S. while the second batch was collected from Mozambique.
The scientists used a simple six-step routine to conduct the test. They also made sure that the test could run on self-collected samples so as to eliminate the need for an extra healthcare provider, equipments or supplies.
The test also manages to cut down on expenses as it would cost $5 per test as compared to $14.90 for the standard test. The cost of the machine to run the tests in developed countries also drops from $17,000 to $1000 while using the new method.
