Sami Eldirdiri, a clinical cytologist at Kenya Aids Vaccine Initiative, explains how the Digital HPV testing machine works. PHOTO | SARAH OOKO |
What you need to know:
Such technologies have the potential of preventing up to 80 per cent of cervical cancer cases as has happened in the developed world.
Mary Cherotich, 45, visited her gynaecologist in 2011 for a routine Pap smear test, which is used to diagnose cervical cancer. The doctor took a sample of her cervical cells for testing.
Thereafter, this specimen was placed on a glass microscope slide and sent to the laboratory for analysis. The cytologists at the laboratory looked at the collected cells under a microscope and spotted some that though appearing abnormal did not look cancerous.
Ms Cherotich was discharged and asked to come for a follow up test the following year. But when she did, it was too late as she now had full blown cervical cancer.
She is among the thousands of Kenyans who due to misdiagnosis succumb to cervical cancer, a leading cause of cancer death among women in the country.
It, therefore, contributes to the high cancer burden in Kenya where 41,000 new cases are detected annually and about 28,000 succumb to the disease.
A positive Pap smear test indicates that a woman has been infected by a bug known as the human papilloma virus (HPV) which is detected as abnormal cells. This group of viruses are responsible for almost all cervical cancer cases worldwide.
Even though the Pap test is often the first step in cervical cancer diagnostics, research shows that it can fail to find abnormal cells that need treatment as frequently as 53 per cent of the time.
The reliability of the test is highly influenced by the quality of sample collected and the skill of the person examining in it. If any of the two are inadequate, then the results will be compromised.
In certain instances samples analysed may fall on a ‘grey’ zone where doctors are unable to tell whether cells have been affected by HPV or not, as it happened to Ms Cherotich.
Therefore, negative Pap smear tests may turn out to be positive while in some cases cells may appear abnormal when they are not.
These challenges will soon be addressed following the recent unveiling of a new diagnosis machine — by the Ministry of Health — known as the Digene Hybrid Capture system for HPV DNA testing. This technology specifically looks for the presence of certain types of HPV which predispose women to cervical cancer.
According to the World Health organisation (WHO), there are more than 100 types of HPV but only 13 of them cause cancer. The two most lethal ones are types 16 and 18 which are responsible for about 70 per cent of all cervical cancer cases worldwide.
The digital testing machine also finds out if the intensity of the HPV infection is high enough to warrant any clinical action. Only samples with a viral load exceeding 5,000 copies are considered positive as they increase cancer risk.
Cervical cells of women found to have a high viral load of high-risk HPV types are further analysed for any abnormal changes. The cells affected by the virus can be destroyed through freezing (cryotherapy) or removed using a cauterising loop. The two treatment strategies prevent the affected cells from becoming cancerous.
Since Pap smear tests rely on structural changes of cells affected HPV which are observed through the human eye (under a microscope), their results are considered subjective.
“They will depend on what the cytologists conducting the test see and how they interpret the findings,” explains Sami Eldirdiri, an expert on the technology from the University Of Nairobi KAVI Institute of Clinical Research.
The HPV DNA testing technology, used in 70 per cent of laboratories worldwide, is however deemed objective as it digitally processes the samples and releases the test results.
“The entire process is automated. After clicking the start button on the machine, you just wait for the machine to generate the results,” he adds.
The wide adoption of this technology in HPV testing has contributed to the decline of cervical cancer cases in the developed world.
It is for this reason that the Bill and Melinda Gates Foundation gave a grant to Qiagen Company, manufacturers of the Digene Hybrid Capture System, to develop a version of the machine that would be affordable and operable in low income settings like Kenya.
This decision was timely since WHO statistics show that of the 270,000 cervical cancer deaths happening globally every year, more than 85 per cent occur in less developed regions.
The dire situation in developing countries is mainly attributed to the lack of appropriate screening technologies that facilitate prompt diagnosis and treatment of fatal HPV infections.
Such technologies have the potential of preventing up to 80 per cent of cervical cancer cases as has happened in the developed world.
The digital HPV DNA testing machine is available at KAVI offices and Nairobi Hospital. The Ministry of Health is also piloting the use of the technology in Kitui County, where the machine is also being used to collect data on the prevalence of cervical cancer in Kenya. Once the pilot is completed, the machine will be deployed to public hospitals.
“We want it to offer cervical cancer screening services to women at no cost under the cover of the National Health Insurance Fund,” notes Dr Jackson Kioko, deputy director of medical services.
However, private health facilities and laboratories can buy the technology directly from Biozeq, the representative of Qiagen Company in Kenya.
The rapid adoption of the digital testing machine is set to bring the technology closer to Kenyans as previously samples had to be shipped abroad for HPV DNA testing.
Research trials have shown that using HPV DNA testing together with Pap smear (co-testing) greatly minimises instances of misdiagnosis in patients.
When Pap smear results are not clear, as was the case with Ms Cherotich, the new technology will enable doctors to determine – with certainty – the presence or absence of cervical cancer.
But HPV testing alone is also a preferred screening method as it alerts patients of the presence of high risk HPV types long before they develop structural changes that can be picked out by the Pap smear under a microscope.
“It allows them to prevent the disease rather than deal with its consequences,” explains George Kaiyare, researcher at KAVI which is piloting the technology in conjunction with the Ministry of Health.
However, Dr Kioko says that for the new technology to have an impact in the fight against cervical cancer in Kenya, it should be integrated with other interventions such as vaccination and screening.
The HPV vaccine only offers protection against two high risk viruses (16 and 18), leaving others that can also cause cancer. Therefore, immunised women are also advised to have regular screenings.
It takes about 15 to 20 years after a HPV infection for cervical cancer to develop in women with normal immune systems. But it can take only five to 10 years in women with weakened immune systems, such as those with untreated HIV infection.
The human papilloma virus is the most common viral infection of the reproductive tract. Most sexually active women and men will be infected at some point in their lives and some may be repeatedly infected thus increasing their risk of cancer.
The virus is sexually transmitted, but penetrative sex is not required for transmission. Skin-to-skin genital contact is a well-recognised mode of transmission. Aside from cervical cancer, the virus is linked to cancers of the anus, vulva, vagina and penis.
