Google is to test a new online medical record service with a hospital group in Cleveland, Ohio, allowing patients to control who gets to see their health information.

The two organisations hope the trial will lead to the creation of a national system for sharing electronic medical records.

The Cleveland Clinic already operates its own electronic personal health record system, eCleveland Clinic MyChart, holding the records of 100,000 patients. It will now invite between 1,500 and 10,000 of them to participate in the trial with Google.

Participants in the trial will be able to exchange data about their prescriptions, conditions and allergies between their Cleveland Clinic record and a "secure Google profile" in a live clinical delivery setting, the hospital group said.

With the data accessible in this way, patients will be able to share it with different doctors, service providers and pharmacies, according to the hospital group.

Google will release further details of its role in the trial later today (21 February).

The search giant was not immediately able to say whether the Google profile that will be used in the Cleveland trial is the same as the Google Account used to access Gmail, iGoogle and other personalised services the company offers. Google usually uses the term "Google Profile" to refer to a kind of online visiting card showing information about a Google Account holder.

For the Cleveland Clinic, one of the attractions of working with Google is that it can offer the record sharing service at no cost to the user or to the clinic, it said.

Google funds its personalised web services by displaying targeted advertising based on what it knows about its users. If this pattern is used with health records it is likely to raise questions about whether sensitive personal information could end up in the hands of marketers.

Privacy is bound to be a concern for potential users of the system for other reasons: health information is sensitive because of the effects that certain conditions can have on job prospects or insurance rates. For those reasons the storage, transmission and use of such information is tightly regulated by the Health Insurance Portability and Accountability Act (HIPAA) in the US.

In its privacy policy, Google already promises not to share sensitive personal information with third parties without prior consent, defining sensitive personal information as "information we know to be related to confidential medical information, racial or ethnic origins, political or religious beliefs or sexuality and tied to personal information."