What is the standard of disclosure required by an expert in the field of medical malpractice?

Finally, "Even though one is under no obligation to speak as to a matter, if he undertakes to do so, either voluntarily or in response to inquiries, he is bound not only to state truly what he tells but also not to suppress of conceal any facts within his knowledge which will materially qualify those stated. If he speaks at all he must make a full and fair disclosure.' [Citation.] Where there is a duty to disclose, the disclosure must be full and complete, and any material concealment or misrepresentation will amount to fraud sufficient to entitle the party injured thereby to an action. [Citation.]' (Pashley v. Pacific Elec. Ry. Co., 25 Cal.2d 226, 235, 153 P.2d 325.)