I am surprised a PCP would even look at saliva test. Most doctors or endocrinologists don't even know about the test.
It would take a rare doctor to give you a diagnosis of adrenal insufficiency using saliva tests. Maybe someone like Dr Rind. Although it is becoming more common.
But yes, if you are below the reference range, that normally means you are lower than 90% of the population.
Do you have the following symptoms:
1. Do you have an afternoon energy crash.
2. Do you get a boost in energy late in the evening, near bed time.
3. Does your mind race in bed.
4. Are you jumpy? Do you startle easy.
5. Do you have a hard time relaxing. Do you always feel the need to be doing something.
6. Do fluids pass right through you. i.e. you need to urinate a lot.
These are all common symptoms of being wired and tired, classic AF symptoms.