What is the test for determining whether a prisoner's civil rights have been abridged as a result of his medical negligence?

In addition, before it can be said that a prisoner's civil rights have been abridged, "the indifference to his medical needs must be substantial. Mere 'indifference,' 'negligence,' or 'medical malpractice' will not support this cause of action." Broughton v. Cutter Lab., 622 F.2d 458, 460 (9th Cir. 1980) (citing Estelle, 429 U.S. at 105-06). See also Wood v. Housewright, 900 F.2d 1332, 1334 (9th Cir. 1990) ("In determining deliberate indifference, we scrutinize the particular facts and look for substantial indifference in the individual case, indicating more than mere negligence or isolated occurrences of neglect.").