Me too, except my data begins in 1972. Put it on an Excel spread sheet in the mid-1990's. An individual test doesn't mean nearly as much as how consistent the numbers are with your long term "normal" and the direction of any trends. The plotted graphs should be viewed like an industrial process control chart. You don't want to be chasing your tail or over-reacting to any small change.
Correct. You can’t manage what you don’t measure and you can’t extrapolate a point.