What is the test for meeting the threshold burden of a claim in an action brought by a plaintiff in a medical malpractice case?

The parties disagree on whether the plaintiff has met the threshold burden. That burden was described by Garson J.A. in Perren v. Lalari, 2010 BCCA 140 at paragraph 32 as follows:

A plaintiff must always prove … that there is a real and substantial possibility of a future event leading to an income loss. … (emphasis in original) If this threshold is met, then: Hypothetical events (such as how the plaintiff’s life would have proceeded without the tortious injury) or future events need not be proven on a balance of probabilities. Instead, they are simply given weight according to their relative likelihood. … (Athey v. Leonati, 1996 CanLII 183 (SCC), [1996] 3 S.C.R. 458 at para. 27 per Major J.).