Two leading researchers warn that the entry of big companies like Microsoft and Google into the field of personal health records could drastically alter the practice of clinical research and raise new challenges to the privacy of patient records.

Microsoft and Google have recently begun offering Web-based personal health records, in a new “personalized, health information economy” in which consumers tell physicians, hospitals and other providers what information to send into their personal records, stored by Microsoft or Google.

The authors say that consumer control of personal data under the new, unregulated Web systems could open the door to all kinds of marketing and false advertising from parties eager for valuable patient information.