Helen Salisbury: Is presumed consent enough for sharing medical data?

Medicine is usually an activity that involves consenting adults, or adults consenting on behalf of their children. Before surgical procedures, especially if the patient will be unconscious, we ask for written consent, but in most other situations verbal consent is enough. Sometimes it’s sought informally (“Shall I examine you now?”), and sometimes consent is implied (for instance, by the patient climbing on a couch or rolling up a sleeve for a blood test). In these situations consent is presumed and, crucially, the patient can withdraw that consent at any time to stop the procedure.

Just how formal we need consent to …