What are the substantial changes?
"Until yesterday, the Agriculture Department used a rapid test called an Elisa and confirmed any positives with a slower immunohistochemistry test, which it calls the "gold standard."
"The Europeans and the Japanese use those tests, but routinely add a confirmatory Western blot test, which is more sensitive."
They added doing the Western Blot, the same technique they use to confirm antibodies for HIV. I believe the immunohistochemistry test didn't work because it uses antibodies specific to single versions of the Canadian strain of these prions, as opposed to the French strain which this cow was found to have.