International preventive health company Screen for Life has recently started operating in Australia and is mailing over-50s, urging them to make an appointment for a $199 stroke screen.

The test involves an ultrasound of the neck to check for hardening of the carotid arteries - blood vessels that supply blood to the brain - which can cause stroke.

''As you age, fatty deposits known as plaque can build up in your arteries. You may not notice any symptoms but the silent danger is there,'' the Screen for Life letter reads.

Health experts say this could lead to unnecessary invasive procedures, as many people have some degree of hardening of the arteries but are not at risk of stroke.

The National Stroke Foundation has distanced itself from the group, posting a warning on its website saying that it does not endorse Screen for Life's services nor does it support medical tests that may be unnecessary.

Victorian Health Services Commissioner Beth Wilson - who received one of the letters at her home address - said there was no scientific evidence that this kind of screening was helpful in people not showing symptoms.

She is concerned that private health-screening companies - they are booming in the United States and Britain but are inadequately regulated - will take off here.

''None of the reputable Australian or international stroke guidelines recommend this type of screening. It is likely to cause a lot of alarm and the letters do nothing to actually allay that alarm. It could also lead to a false sense of security - someone's screened and thinks they're not at risk when these tests cannot establish that,'' Ms Wilson said. ''There's nothing illegal in what's being done that I can see, but you do have to question the ethics of it.''

Stroke expert Professor Stephen Davis, director of neurology at the Royal Melbourne Hospital, said he was also concerned. "There is no high-quality study anywhere in the world that has shown that screening of this type reduces the risk of stroke,'' he said. ''Ultrasound for stroke is only useful when recommended by a doctor where the patient has had symptoms such as abnormality of speech, sudden vision weakness, general weakness, weakness in the arm or unsteadiness.''

However, Professor Scott Kitchener, consulting medical director for Screen for Life, defended the service and said the earlier cardiovascular disease could be detected the better.

''It's probably akin to searching for melanomas or breast cancer before they become symptomatic,'' he said. ''This is a screening test that identifies whether somebody is likely to have a disease present to a level that it's now cost-effective to do a definitive diagnostic test. If that diagnostic test leads to an intervention that can change the course of the disease and improve the person's quality or length of life then that screening is worthwhile.''

The National Stroke Foundation said if people were worried about cardiovascular disease including stroke, they should visit their doctor and ask for an assessment. Tests ordered by GPs were often partially or totally covered by Medicare.

■jstark@theage.com.au