This is a great question and a debate among privacy experts. There are a few issues at stake here: 1) your data is used for many activities in health care that you as a consumer have no knowledge, 2) those activities may lead to you as in individual being identified as an over utilizer of health care services and 3) identification of over utilization is a sign of increased health risk which may indicate that you are a poor candidate for health insurance benefits, certain treatments or you may be targeted for programs that aim to decrease or stop your over utilization of health care resources. So, poor privacy constraints - or at least lack of transparency for how your data is used, for what purpose, for how long and which outcome measurement is the real risk.
RE: Sharing & Withholding Medical Information at the Point of Care