Doctors and labs in this country are not dependable when it comes to finding any parasites. I've seen liver flukes when I've done liver flushes. Most peope see them or evidence of them then.
I believe more people then we think have parasites. My sister had a ton of various kinds of parasites or I would not have ever believed it. She was a average American with average eating habits and very clean. She passed them when she was juice fasting so she could see them - I convinced her to save one to prove to the doctor that she had them... she fished one out of the toilet and took it to her doc who said it was a beef Tapeworm - it was 5 1/2 feet long. She said I wouldn't believe what all came out of her and the beef tape that I saw was nothing compared to what had already passed. It made me a believer.
I've heard people sey they've sent stool sameples with parasites in them to the lab - and the test came back negative. Sorry, I don't trust doctors or labs at all when it comes to parasites and would not waste my money.