What is the test for negligence in a medical malpractice case?

Counsel for the plaintiff has cited the following statement from the headnote in Hedley v. Byrne (supra) at 575: "If, in the ordinary course of business or professional affairs, a person seeks information or advice from another, who is not under contractual or fiduciary obligation to give the information or advice, in circumstances in which a reasonable man so asked would know that he was being trusted or that his skill or judgment was being relied on, and the person asked chooses to give the information or advice without clearly so qualifying his answer so as to show that he does not accept responsibility, then the person replying accepts the legal duty to exercise such care as the circumstances require in making his reply; and for failure to exercise that care an action for negligence will lie if damage results."