I haven't had it ordered for me, but I did the collection when I was working on the medical ward. That was decades ago. I didn't know they still did it. Basically, you just collect your poop for 24 hours after eating a prescribed diet with a specific amount of fat in it. It determines if you are digesting and absorbing fat in your gut. It does not provide a specific diagnosis, just a type of malabsorption.
Are they looking for something specific?
Jan