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."
A new way of screening for ovarian cancer is showing "potential", according to researchers in the US.