>>95436they're called ineffective because that's basically a roulette. doctor views a micro piece of your shit in microscope for worm eggs. here are the possibilities which make so much false negatives:
1. he doesn't grab piece with eggs in it. this test works normally only if infection is very severe and eggs are EVERYWHERE inside your shit.
2. he thinks that eggs are pieces of food, dirt or whatever else.
3. he isn't experienced enough to find eggs (same as 2)
4. nobody actually inspects your shit and they just send you a negative
blood test won't indicate any parasites if there are some in your bloodstream, same reasons as for stool + they're not looking exactly for parasites