This is a really complicated subject. I do it for a living sometimes!
There are many tests, they all measure something different and are not
comparable. Many of the suppliers claims need careful consideration
(I'm being tactful). For example one well promoted test a few years ago
sensitivity to measured toxins was totally obscured by natural
substances such as manganese.
Be very careful. Email me via my website if you want more detail.
Please put the world back how you found it before leaving. Others may want to
use it later.