What is the test for qualified expert testimony in a medical malpractice case?

"A person is qualified to testify as an expert if he has special knowledge, skill, experience, training, or education sufficient to qualify him as an expert on the subject to which his testimony relates. The competency of an expert is relative to the topic and fields of knowledge about which the person is asked to make a statement. A trial court's decision on this ground is subject to the abuse of discretion standard." (People v. Fudge (1994) 7 Cal.4th 1075, 1115, 31 Cal.Rptr.2d 321, 875 P.2d 36, internal quotation marks and citations omitted.)