@SOC - I think Dr. Edwards already gave a good explanation, and I'd agree with everything he said.
I'll add a bit.
Doctors are not just looking at reference ranges. They are looking for evidence that supports a diagnosis. Often a panel of tests is run, looking for information that suggests a particular diagnosis. Say you're worried about disease X based on clinical presentation, and it causes an elevation in lab marker Y. If you get back the report and Y is reduced and just below normal range, that doesn't support your potential diagnosis of disease X, so you'll likely dismiss it unless, in isolation, it suggests another disease that fits clinically with what you are observing.
Lab tests - or any medical tests - usually cannot be interpreted in isolation, which is why docs generally should be involved in the interpretation. Various studies must be correlated clinically with signs, symptoms, and history, as well as with other studies.
Many ME patients will get extensive lab work and have a number of results that, just by chance, fall outside the normal reference range. Sometimes, these results are replicable and it is something the patient frequently sees. I have some results like this. This becomes interesting to me if other patients are frequently reporting this result, or even more so if published papers document this abnormality or tendency in ME patients. However, if it is totally isolated, then I do not worry too much about it in general, although I will keep it in the back of my mind, as it may be something that later gives me a clue.
Some patients are genetically programmed to have certain results be abnormal, although not pathogenically. I have very low triglycerides. I am often outside the normal reference range (it can be 20 or 30 sometimes), no matter what I eat, what I weigh, or how bad my cholesterol is. I never knew why, but it's not rare in my family (on one side). Recently I found out I have a very rare mutation in the APOC3 gene which is involved in lipid transport. It's essentially a knockout in one allele, leaving only one functional copy. This was studied in the NEJM recently in a cohort of over 75,000 people, and found to have an allele frequency of about 1 in 720 - and to reduce rates of heart disease and stroke pretty dramatically, and it's being studied in the development of new drugs. The point is, I could have spent years worrying about why my triglycerides were out of the normal range. There is a reason - but I didn't know if for 20 yrs or so. Now I know it, and it's not something to be worried about. Docs didn't worry either because they couldn't think of a disease it would indicate (high would be another story).
We're all different genetically, and may have abnormal results for that reason (as Dr. Edwards mentions, CRP baseline values vary by a factor of up to 5 - this is probably genetically determined). You have to interpret a CRP vs a baseline. Other results just tend to fluctuate a lot, such as lymphocyte populations, and this occurs in healthy people too. Sometimes, it's an indication of a problem, but more often, it's nothing. If the doc isn't sure, or is a bit worried, follow up or repeat testing is warranted. Labs make errors too, which can sometimes give a flukey result.
I think the real problem is that treating physicians, when they are treating populations of patients with ME or other illnesses where patients have no choice but to take an active role if they want good treatment, do not explain why results are dismissed. I urge you to question them and just ask for an explanation of why the result is not concerning. The physician has probably thought about it and has a reason for dismissing it. Also, if you are concerned, they will often offer a repeat test to make sure things are ok.