2 tests better than one for cervical cancer

100% accuracy with Pap smear and human papilloma virus test: Study

A local study has proven that cervical cancer can be tested for with greater accuracy by combining a Pap smear with a test for certain types of the human papilloma virus (HPV) which cause the cancer.

This co-testing method detected all cases of cervical cancer, compared with just two-thirds of cases if only Pap smears were used, a study by the Singapore General Hospital (SGH) has found.

Cervical cancer, the 10th most common cancer among women here, is preventable when detected at the pre-cancerous stage, or before the cells turn cancerous. There are usually no signs or symptoms at this stage, and it can be detected only through a screening.

While a Pap smear checks for pre-cancerous and cancerous cells, it has its limitations, noted Professor Tay Sun Kuie, a senior consultant at the department of obstetrics and gynaecology at SGH who was involved in the study.

"The Pap smear alone would not be able to pick up as many pre-cancerous and cancerous cells as co-testing because some of the abnormal cells may be too few for the Pap smear to detect," he said.

The HPV test still needs to be combined with a Pap smear to accurately test for cervical cancer. This is because testing positive in an HPV test does not always mean a woman has cervical cancer - the infection leads to a higher risk of such cancer in only around 20 to 30 per cent of cases.

"However, the HPV test is a molecular test, and you only need one copy of the viral gene to be detected, and that one copy will be amplified into thousands of copies, so it can detect more," he added.

The co-testing method has been used in the United States since 2014, he noted.

The HPV test still needs to be combined with a Pap smear to accurately test for cervical cancer.

This is because testing positive in an HPV test does not always mean a woman has cervical cancer - the infection leads to a higher risk of such cancer in only around 20 to 30 per cent of cases.

Nearly 1,900 women above 25 who underwent co-testing between November 2013 and August 2014 took part in the SGH study.

With the increased accuracy of this method, women need to go for co-testing only once every five years, instead of the recommended once every three years for a Pap smear, said Prof Tay.

But co-testing costs about $200 - four times the cost of a Pap smear.

Since November 2013, around half of the 10,000 women screened at SGH for cervical cancer have opted for co-testing. It is currently the only public hospital to offer co-testing here.

There are around 201 cases of cervical cancer reported here every year, but the number has been falling since 1985, mainly due to more women going for screening, said Prof Tay.

Cervical cancer can affect females as young as 14, although the average age when it is first diagnosed is 41.

A version of this article appeared in the print edition of The Straits Times on October 06, 2016, with the headline '2 tests better than one for cervical cancer'. Print Edition | Subscribe