With regards to "other" labs, I'm sure fixatives are used, and I'm sure these can affect the results.
Did you have computer lab tests done? Computer robots can only be "trained" to look for something, and if the "robot" doesn't recognise something, well I presume it would be ignored or be classed as "negative".
Anyway, more to the point, I think if you read through RHR's site, starting with how they got started, I'm sure this would benefit you in maybe making a decision as to how you proceed. I'm only concerned for you that you may be wasting (valuable) time and money too on unreliable tests. I can understand you are skeptical, I've been there, many times. But I'm so glad I found RHR. (I'm sure you've seen my micrographs).
Please take the time to read through the whole site, but start with the facts, I'm sure you will see where the difference lies between RHR and other labs.