Blood test tests for what is in your blood (leaking from wherever it's leaking from) and that would be your immunoglobulins. Microbiome test looks and your stool and sees of you're harboring bacteria in your guts that are out of proportion (mine were way out of proportion because I'm HLA-B27+). Great question about Rifaximin. You don't have to take it for life if you're not HLA-B27+, and if you are you need to cycle it after about 6 months to a year (you could go longer, but it's good to play it safe.) The reason is it up-regulates triglyceride uptake in the intestines and can lead to fatty liver. However, it's very anti-inflammatory. I brought that paper to a GI specialist and told him I had IBS/bowl problems and was HLA-B27+ and that I'd tried a friend's leftover bottle of Rifaximin and that it worked well for me. He wrote a script that same day, impressed by my research. It helped ME a lot, in the beginning. It's still effective, but my issues seemed to evolve and it is only about half as effective as it once was. I still take it though. It's one of the safest antibiotics with least side-effects (as it isn't absorbed into the body) that there is. It also doesn't seem to have bacteria form much resistance to it, which is interesting. It is actually a byproduct of a certain other bacteria's fermentation process. It turns out that certain good bacteria, or I should say compatible with us biologically, create byproducts that are themselves antibacterial and keep out infection. Even in very serious infections, people can completely resist certain disease, or greatly reduce their duration of sickness... Simply by having a certain type of bacteria in their gut. This can even affect inflammation at sites not in the guts, such as lung infections, etc. It's all really fascinating stuff!