Cervical Cancer Risks: HPV Infection

HPV cannot be cultivated

Cervical cancer takes years to develop

HPV Vaccination is best done when young.

Professor Tay Sun Kuie, Senior Consultant, Department of Obstetrics and Gynaecology, and Dr Lynette Oon, Senior Consultant, Department of Pathology shares on HPV infections and their tests.

Not everyone who catches the infection will get cancer, in part because the virus is naturally cleared from the body. But reinfection is possible. “For a virus to induce a cancer over a period of time, the risk is 0.005 per cent. So, one shouldn’t worry that once diagnosed with the infection, she will have cancer one day. The majority don’t,” said Prof Tay.

Still, to play it safe, women should consider regular cervical screening and vaccination. Screening detects disease at the early stage, when it is more easily treated, or at pre-cancer stage, when abnormal cells appear. Vaccination can help prevent HPV infection, and is best done when young. “Vaccines are preventive measures bolstered by the immune system, so the vaccine’s effectiveness is halved when received later in life,” said Prof Tay, adding that girls as young as nine can be given the vaccine although 12 is the age that is more commonly recommended.

HPV cannot be cultivated

The human papillomavirus (HPV) cannot be cultured in the laboratory. To determine if someone is infected with it, the presence of the gene or its genetic makeup needs to be established.

To do this, a technique known as polymerase chain reaction or PCR is used, said Dr Lynette Oon, Senior Consultant, Department of Pathology, Singapore General Hospital. PCR essentially generates millions of copies of a DNA sequence so that tests can be applied to detect the virus in the lab.

“After PCR, we then use reverse line blot hybridisation, where each sample is run onto a strip to identify the HPV type present,” Dr Oon said.

PCR, commonly used in research and hospital laboratories, makes use of thermal cycling or repeated cycles of heating and cooling to separate the DNA and to replicate the fragments.

Cervical cancer takes years to develop

HPV is mainly transmitted through sexual contact
Most HPV infections clear on their own without treatment, with 90 per cent cleared within three years
It takes 15-20 years for cervical cancer to develop in women with normal immune systems, but 5-10 in those with weakened immune systems, such as those with untreated HIV infection
The high-risk HPV types – 51, 16, 52, 58, 66 and 18 – and low-risk – 62, 61, 84, 72 and 53 – are unique to Singapore
Four of the five most common HPV sub-types found in women in Singapore are high-risk
Low-risk, non-cancer causing HPV types can cause unpleasant but non-life-threatening genital warts
HPV is common but shows a wide geographical variation, with the highest prevalence in Africa and Central America

Ref: Q15

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