This makes it the deadliest gynaecological cancer, and has led to it being dubbed "the silent killer".
In Britain, there are more than 7,000 cases a year - and 4,300 deaths, about one every two hours.
Just a third of women live for at least ten years after diagnosis - making it more than twice as deadly as breast cancer.
Early diagnosis more than doubles a woman's odds of survival but scientists have struggled to find a way of spotting the disease before it takes hold.
But when Georgia Institute of Technology researchers looked at the blood of 46 women in the early stages of the disease and that of 49 healthy women, the cancerous samples contained different levels of 16 proteins compared with the healthy ones.
Some were found in higher concentrations in the blood of women with the disease, while the level of others had dropped.
The differing proportions gave a distinctive chemical fingerprint, allowing the researchers to distinguish the cancer patients from their healthy counterparts with complete accuracy.
More research is needed on a bigger and more ethnically diverse group of women, but if the test fulfils its promise, it could be suitable for a large-scale screening programme within three years.
The NHS would have to decide whether the benefits would outweigh the cost of screening millions of women. One option would be to focus on those whose genes put them at risk of developing the disease. Professor John McDonald, of the research team, said: "We think our results show great promise and we plan to validate our findings across much larger samples."
Katherine Taylor, from the charity Ovarian Cancer Action, said: "Tragically, a woman dies of ovarian cancer every two hours in the UK, and at present there is no effective screening tool.
"The earlier it is diagnosed the better. So it's particularly important for women to be aware of the signs and symptoms.
"These are persistent tummy pain, persistent bloating, feeling full more quickly after eating and needing to pee more often.
"If you experience these, and they are unusual for you, keep a symptoms diary and take it to your GP."
Dr Simon Newman, of Target Ovarian Cancer, said: "It is exciting preliminary research. It's crucial to diagnose ovarian cancer promptly, as up to 90 per cent of women would live for five or more years if diagnosed at the earliest stage.
"However, this highly promising discovery needs significant further development and validation in large clinical trials before we know if it is suitable for screening the general population and works as well as predicted."
- Daily Mail
