What is the most accurate testing avalible for Parasites?

I have done many stool tests (some containing visible segments of what I am sure is Tapeworm) and they have all come back negative. This is something ive seen repeated on this site, so I have no faith in stool tests now.

What are the other methods of testing for parasites that are accurate? ELISA blood testing or a scan or something? Would an X-Ray show parasites?

ANY help is greatly appreciated!

Thanks