In a medical malpractice case, in what circumstances can a patient impeach a doctor's credibility?

In a second medical malpractice case, Yarborough v. Cattani , 43 Misc. 3d 785, 982 N.Y.S.2d 716, the findings by the OPMC of incompetence in a doctor's delegating post-operative care to his non-physician office staff were inadmissible and general statements at the hearing about the doctor's credibility were not facts that could be used by the patient to impeach; however, statements that doctor's conduct fell below the standard for honest reporting could be used by patient to impeach doctor's credibility.