I read people on other threads talking about uBiome and American Gut Project. Do these people do the same tests as blue horizon and direct labs and do you need a doctor for them?
These are very different tests from the standard CDSA that you are referring to.
uBiome, American Gut (both US based) and RedLabs in Belgium sequence the DNA of all your gut bacteria (uBiome seem to be including Archaea and Eukaryota also though I'm not sure how extensive the latter is). In other words they give a comprehensive picture of all the bacteria in your gut, not just the few that can be cultured.
uBiome and American gut are crowd-funded initiatives and you can order them directly from the website. You receive the results. There is information on the websites, including plenty of comparison to results from the community being tested, but no interpretation.
RedLabs requires a doctor's name on the order form and results are sent to the doctor. They are a research-based lab and don't interpret the results. They say you should discuss them with your doctor. However I doubt that many doctors would have any clue. KDM uses this test and works closely with the lab. He does have a clue about what results mean but he is definitely an exception.
Traditional CDSA tests look at several things. This include different measures of digestive efficiency, short chain fatty acid production (these are produced by your gut bacteria and give an idea of the balance of the flora), some parasitology and culture of some bacterial and fungal species.
The first part of the test can give some useful information (though it is a lot of money to pay for what you end up with), but in my opinion, the parasitology and culture results are usually not particularly valuable and may be downright misleading.
The problem is that many fragile parasites are missed because the stool is not usually preserved. There are some tests that do include preservation (samples of stool are immediately placed into preservative) so you would need to check that you have this type of test. The parasites are then identified by observation. It has the potential to detect anything present but lacks sensitivity.
A more sensitive type of parasitology test is PCR based, but this can detect only the species it is directed against. If you had something else, it would be missed.
As for the bacterial and fungal culture, these are the bread and butter tests that have been around for years and have given us a completely distorted idea of what is in the gut. The problem is that they select for aerotolerant species and the vast majority of the gut constituents are anaerobes. Almost all of the flora is missed by such tests.
The DNA based tests will give you the compete picture of what is really in your gut. However they are essentially research-based. You need to work hard at understanding what the results mean. It's a bit like doing a 23andme test.