If a test cannot be validated, then it's not useful. If you find the bacteria in 100% of the samples you get from CFS patients but have never tested it against healthy controls, then how do you know it's not present there as well?
Yes that is right.
You really need to perform the same urine culture test on healthy controls as well as ME/CFS patients, and compare the results.
You can only state that ME/CFS patients have a urinary tract or kidney infection if you find these infections significantly more often in patients compared to controls. That research must be done before you can say that ME/CFS patients have kidney infections.
Note that Dr Igor Markov also detects these kidney infections in patients with other diseases. In fact I have read that Dr Markov tends to diagnose many of his patients with a kidney infection, and then treats with an autovaccine. So he finds this infection not just in his ME/CFS patients.
This means that these kidney infections are not unique to ME/CFS, and thus cannot be the sole cause of ME/CFS. However, such kidney infections could be playing a
causal role in ME/CFS, just as SIBO may be playing a causal role in ME/CFS (or if not playing a causal role, may worsen symptoms like fatigue).
Whether ME/CFS patients do have kidney infections more commonly than healthy controls is, however, a separate issue to the question of the benefit of an autovaccine for ME/CFS.
Even if ME/CFS patients did not have kidney infections more commonly than controls, it is still possible that an autovaccine might benefit, since that vaccine may be strengthening immune responses to pathogens carried by that individual in the kidneys and throughout the body.