Ovarian cancer does not generally cause symptoms in the early stages. When symptoms do occur, they are usually a result of the cancer growing and causing pressure or pain.

Ovarian cancer is responsible for the deaths of nearly 5,000 women a year in Britain and has been called the "silent killer" because it is usually advanced and hard to treat by the time symptoms appear.

The new test has the potential to save lives by allowing identification of the disease at a stage when it can be effectively treated. But, with an accuracy of 95 percent, it is still not precise enough to be used in national screening programs.

At present there is no way to detect the disease reliably at an early, curable stage.

Just under 7,000 women are diagnosed with ovarian cancer each year in the United Kingdom and a large proportion -- almost 4,700 -- will die of the disease. It kills more than 300 women a year in Scotland.

The new test was developed by scientists in the United States led by Dr Gil Mor, from the Yale School of Medicine in New Haven, Connecticut. It relies on four marker proteins, whittled down from an initial list of 169. The four -- leptin, prolactin, osteopontin and insulin-like growth factor II -- identified cancer with 95 percent accuracy in a test group of more than 200 women.

Each of the proteins had previously been suggested as a possible cancer biomarker. But, in the study, no protein on its own could completely distinguish cancer patients from healthy participants.

The findings were reported in the journal Proceedings of the National Academy of Sciences.

The researchers pointed out that the test would have to be improved before it was good enough for national screening, which required an accuracy of at least 99.6 per cent.

They wrote: "Given the rarity of ovarian cancer, very low levels of false positive classification will result in a large number of women being incorrectly classified as potentially having ovarian cancer.

"Thus, there is a significant need for further improvement of the four-analyte test reported here if the assay is to be used for general population screening."

Dr. James Mackay, a consultant clinical genetic oncologist with the charity Cancer Research UK, welcomed the study.

He said: "This is an interesting research finding. The next stage in investigating this would be to use these markers in a prospective study either of high-risk women or a randomized study of women at normal risk.

"Cancer Research UK supports studies of ovarian screening in both high-risk and normal-risk women and we are confident that our research teams would be willing to collaborate with the teams which have published these findings."

Ovarian cancer is the fourth most common cancer among women in the UK and develops in cells of the ovary.

The risk increases with age. Most ovarian cancers occur in women after they have gone through the menopause -- more than half in women over the age of 65.

Women who have never been pregnant are more likely to develop ovarian cancer than women who have had children, as are those who have used fertility drugs. Women who have taken oral contraceptives also have a lower risk.

There are no screening tests currently recommended for the general population, although there are clinical trials to determine if screening could detect ovarian cancer early and reduce the risk of death.

Ovarian cancer does not generally cause symptoms in the early stages. When symptoms do occur, they are usually a result of the cancer growing and causing pressure or pain.

Potential symptoms include prolonged swelling of the abdomen, digestive problems, weight loss and a frequent need to urinate. Ovarian cancer is thought to be far easier to treat if detected early.

A spokesman for Cancer Research UK Scotland said: "Any research into how the disease can be stemmed is welcome."

Sherry Salway Black, the executive director of the US-based Ovarian Cancer National Alliance, said: "We've been hoping for a while that proteins could revolutionize early screening for ovarian cancer, as well as other types of cancer.

"The symptoms of ovarian cancer are subtle, so the disease is not being picked up early enough in a lot of women who are instead being diagnosed with other ailments.

"If the effectiveness of this research rises to 99.6 percent, the science will hopefully put us out of a job and women can be widely screened."