Tumours in the ovaries are hard to detect in the earliest stages meaning it can be too late to treat them effectively by the time they are found.
A trial of 4,051 women, reported in the journal Cancer, showed the method could identify those needing treatment.
But a huge study taking place in the UK will give a final verdict on the test when it is completed in 2015.
There is a survival rate of up to 90% when ovarian cancer is caught early, compared with less than 30% if it is discovered in the later stages.
Unlike other cancers, the symptoms, such as pelvic and abdominal pain or persistent bloating, are often put down to other common ailments and the tumour can be missed.
There is no mass screening programme to detect the cancer either.
Scientists already know that levels of a protein in the blood, called CA125, are often higher with ovarian cancer.
However, it is too unreliable on its own. It misses some patients and tells others they have the cancer when they are actually healthy.
Researchers are now testing the idea of using the blood test to sort patients in risk groups based on levels of CA125. Instead of going straight for surgery, low-risk patients are tested again in a year, medium-risk ones after three months and high-risk patients have an ultrasound scan to hunt for tumours.
The US study, at the University of Texas, followed post-menopausal women for 11 years on average.
Ten women had surgery based on their ultrasound scan and all the cancers detected were at an early stage.
Researcher Dr Karen Lu told the BBC: "Clinical practice definitely should not change from our study, but it gives us an insight - we didn't get a lot of false positives."
She said the UK study of 50,000 people would give definitive results: "There are two big questions - do we see cancers at an earlier stage and do we decrease the number of deaths."
Dr Sarah Blagden, from the Ovarian Cancer Action research centre, said: "Relative to the trial under way in the in the UK , this is a small study, but it does show that effective ovarian screening is possible.
"In 2015 the results of the UKCTOCs study will become available and the results are eagerly anticipated, more so now that this American study has produced such encouraging results."
Annwen Jones, the chief executive at Target Ovarian Cancer, said: "The results of this study are without doubt very positive, and we should take hope from that.
"Early detection of ovarian cancer will be the key to transforming survival rates.  However, this study is very small, and there is no guarantee that the results will be replicated on a larger scale."

The sixth form at Halewood Academy in Knowsley will shut in August 2017 after the Department for Education agreed it could stop providing A-levels.
Principal Gary Evans said it was "sad" but left the academy in a stronger financial position.
Education chiefs pledged to get an another A level plan in place by 2017.
Mr Evans said: "We shall continue to work extensively with other post-16 providers to ensure that all of our students remain in education or training once they leave the academy.
"Discussions are also taking place for a future potential post-16 joint venture across Knowsley," he said.
Knowsley has the lowest proportion of students taking A-levels in England at 2% and has among the lowest university entry rates in England.
A letter to the school from parliamentary undersecretary of state for schools, Lord Nash, outlined the plan.
He said after considering the quality of provision, the impact on existing students and the availability of post-16 education in the area  "I have agreed their request to close the sixth form".
Knowsley councillor Gary See said the local authority was "naturally disappointed with this outcome" but pleased there was "some clarity for the Academy and its students".
He said due to the school's academy status, the council had "no powers to intervene" but had committed to working with the government to establish "new sixth form provision from September 2017".
Parents at the school had protested against the closure, arguing it "is letting down the children of this community" and could block their ambitions.
Students who are part-way through their studies will be able to continue at the sixth form.
A new way of screening for ovarian cancer is showing "potential", according to researchers in the US.
[NEXT_CONCEPT]
A Merseyside borough will have no A-level provision after the government approved the closure of the area's only sixth form offering the qualification.