<<Disclaimer: Verify this information before applying it to your situation.>>
 
Unfortunately because these tests are not standardised, there is no one
set of normal ranges.  Each laboratory in the USA has to generate their
own normal range.  The scales are not comparable, So follow up tst
results done at another lab may not be accurately compared with teh
results obtained at the first lab.. anothe problem is that there is
tremendous consolidation in the laboroatory world with bidding processes
making it possible that your provider may end up sending later specimens
to different labs.  It does not mean that any one lab is better than
another, just different.
Joe Murray
Not Medical Advice