If you are cathed and negative, you fly that same day.
If you are cathed and not negative, you probalbly wanted to know anyway.
However, there are two ways to view this: First, unless you are a person who needs a "test" to push you to (1) Eating right (2) Exercising (3) maintaining a lean body mass, (4) controlling glucose intolerance, then you would do all those things you should do anyway and a Cath is needless additional risk.
Be honest with yourself. Which one are you? Do you need the Cath to push your behaviors?