What is the legal test for making a diagnostic error in a patient?

In Agate v. Burrows, [1988] B.C.J. No. 586 (S.C.), Mr. Justice Trainor made the following comments with respect to diagnostic errors and the use of judgment in considering the value of further testing: In each diagnosis, the exercise of reasonable care, skill and judgment is required. A mistaken diagnosis may not be a negligent one. A mistaken diagnosis becomes a negligent one if the mistake results from a failure to exercise reasonable care, skill and judgment. It can result from the failure to collect necessary factual data through appropriate tests or a patient’s history. However, the obligation to have a further test done is a question of medical judgment to be exercised on the basis of information then available and the possible gain or additional information which might be learned from such a test.

One cannot retrospectively prefer one accepted school of thought over another. In Fairley v. Waterman, et al, 2002 BCSC 10 at paras. 11 and 42, Mr. Justice Wong stated that: