It tests for specific antibodies from a specific parasite only. There are thousands of kinds of parasites. And it's not that accurate according to the medical schools.
For other tests, stool samples for (some) intestinal parasites are even less accurate. And it's the same thing, it's always for specific parasites.
To me it makes more sense to spend $20 and make sure you're clear of parasites than to potentially spend lots of time and money ($30 per test of which there could be hundreds) and still not know for sure.
You guys have no experience with this, why are you pretending to be experts?