LONDON (Reuters) - A do-it-yourself test for cervical cancer could help prevent thousands of cases of the disease in women who don't have easy or regular access to smear tests, scientists said on Wednesday.

The DIY test, which detects the human papillomavirus (HPV) responsible for cervical cancer, was widely accepted in a trial involving 20,000 women in Mexico and was more effective than traditional smear tests at picking up early signs of disease.

British researchers who helped develop the test and led the trial said the results, published in the Lancet medical journal, suggest the DIY kit has the potential to help thousands of women who live in countries where smear testing is difficult or impossible.

Smear tests are conducted by a nurse or doctor and checked manually by a cytologist who makes a judgment after examining a sample under a microscope. The DIY test can be taken by a woman at home and the sample is then assessed by an automated system.

Cancer of the cervix is the second most common cancer in women worldwide, with about 500,000 new cases and 250,000 deaths each year, according to the World Health Organisation.

Virtually all cervical cancer cases are linked to genital infection with HPV, the most common viral infection of the reproductive tract.

Cervical cancer is more common and more deadly in countries where women have no access to screening, meaning cases are often detected too late for treatment to work.

A study in September by the Institute for Health Metrics and Evaluation (IHME) at the University of Washington found that both breast and cervical cancer cases and deaths are rising in many countries, especially in poorer nations where more women are dying at younger ages.

In wealthier developed countries, cervical screening programs have been in place for many years, and more recently, national immunization programs using vaccines from drugmakers Merck and GlaxoSmithKline have been launched to protect girls from HPV.

Attila Lorincz, a professor of molecular epidemiology at Queen Mary, University of London, who worked on the trial of the DIY test, said it could also help some women in wealthier nations who will not or cannot have smear tests in a clinic and are declined HPV vaccination.

"Unlike many forms of disease, we can actually prevent cervical cancer -- but only if women have access to screening or if young girls are vaccinated against the virus," he said in a statement.

In the trial in Mexico, around half of the 20,000 volunteers took the DIY test of vaginal samples collected at home, while the other half went to clinics for smear tests.

The results, published in the Lancet journal, showed the DIY test picked up more than four times as many cases of cervical cancer and more than three times as many cases of a pre-cancer condition called cervical intraepithelial neoplasia, which can be treated to prevent the disease developing.

Crucially, uptake for the at-home test was higher than for the smear test, Lorincz said, suggesting that women prefer this type of screening.

"Our findings show that women are happy to take the test and that it is very sensitive at picking up women who are at risk of developing cancer," he said. "This sensitivity is vital for a woman who may only get tested once or twice in her life."

The research team said the test still has limitations. For example, it tends to produce more so-called "false positives" -- picking up women who after further tests turn out to be healthy -- and this adds to the burden on health care services. They said further research was needed to address these problems.

(Editing by Karolina Tagaris)