Smear test: tools of the trade (Image: Saturn Stills/Science Photo Library)

Dread going for a smear test? A simple urine test can pick up the human papilloma virus (HPV) that causes cervical cancer. Though it’s not as accurate as sampling viral DNA from the cervix itself, the test might benefit women who are too busy or scared to have a cervical swab taken, or who live in developing countries where the infrastructure for conventional smear tests is less developed.

Traditional cytology-based smear tests involve using a speculum to hold the vagina open, while a small brush is used to collect cells from the cervix, which are then assessed for pre-cancerous changes using a microscope. “The advantage is that if you have an abnormal result, there is a reasonable chance that you have an underlying abnormality,” says Henry Kitchener at the Institute of Cancer Sciences in Manchester, UK, who was not involved in the current study.

More recently, DNA tests have been developed that test for HPV directly – again by taking a sample from the cervix. This is more sensitive than a conventional smear test meaning that those who test negative are very unlikely to develop cervical cancer in the near future. But those who test positive don’t necessarily have cancer – their cervix may be perfectly healthy – so a positive DNA test needs to be followed up with a physical examination.


Cancer screening

DNA testing for HPV is being piloted in the UK, and was recently incorporated into US guidelines for cervical cancer screening .

Neha Pathak at Barts and The London School of Medicine and her colleagues combined the results of 14 clinical trials of urine testing and compared the results against the new cervical DNA test. Urine tests could correctly identify 87 per cent of HPV positive samples, and 94 per cent of negative samples.

“It suggests urine testing is definitely something worth investigating further,” says Pathak.

Unfortunately, data doesn’t exist that would allow urine testing to be compared with more traditional smear tests – something Pathak says should be investigated in any future trials.

HPV tests for all

However, cervical HPV DNA testing is already known to be more sensitive than microscope-based methods. “It may be that the urinary HPV test is as good as a cytology sample,” says Kitchener.

Even so, urine-based HPV testing is unlikely to replace cervical HPV testing completely. “The actual test in itself isn’t a better test,” Kitchener adds. “But it is another way of obtaining results from the lower genital tract, and it may well be the way forward for women who don’t otherwise engage with screening.”

It could also be useful in developing countries where rates of cervical cancer are often far higher, and the infrastructure for screening and preventative treatment is lacking.

“We’re not saying that this is a direct replacement for cervical testing, but it is something that could be rolled out a little more easily,” Pathak says.

Journal reference: BMJ, DOI: 10.1136/bmj.g5264