From what I've read from good sources,you need more than just a blood test to detect Every single parasite you could possibly be infected with.
I wouldn't even bother with getting anymore tests anyway- YOu know what you saw. Unless you have virtually no stomach acid in your body to digest food whatsoever, and you just ate spaghetti, -- it no doubt is a round worm.
I can't say it is acarius-- but a 10" round worm sounds pretty close to one.
If you ever experience any exzema or rashes from time to time, that is also a good clue-in.