Kingston, Ontario — THERE was no mistaking the diagnostic significance of that little red stick inside a deep blue cell: The Auer rod meant the mystery patient had acute myelogenous leukemia. As slide after slide went by, her bone marrow told a story: treatment, remission, relapse, treatment, remission, remission, remission.

I was reading these marrows in 1987, but the samples had been drawn in 1978 and 1979. Median survival of that lethal disease with treatment was about 18 months; however, given that she had already relapsed once, I knew that she had to be dead. Probably someone was being sued, and that was why my hematology colleagues had asked for a blind reading.

Imagining an aggressive cross-examination in court, I emphasized in my report that I knew neither the history nor why I was reading the marrows. After the work was submitted, I asked the treating physician what was going on. She smiled and said that my report had been sent to the Vatican. This leukemia case was being considered as the final miracle in the dossier of Marie-Marguerite d’Youville, the founder of the Order of Sisters of Charity of Montreal and a candidate to become the first Canadian-born saint.

As in the case of Mother Teresa, who was canonized Sunday by Pope Francis, miracles are still used as evidence that the candidate is in heaven and had interceded with God in response to a petition. Two miracles, usually cures that defy natural explanation, are generally required. For Mother Teresa, the Vatican concluded that prayers to her led to the disappearance of an Indian woman’s incurable tumor and the sudden recovery of a Brazilian man with a brain infection.