Usually labs will send you their interpretation of the test, but Andy's book will give you a deeper understanding of the results esp with regard to mercury.
For instance TEI (Trace Elements Inc) will ignore mercury as an issue if it doesn't show up in the test, whereas Andy's interpretation is that this could indicate you're not *excreting* it properly and it's locked into the tissues (as Johnny said for Autistic kids, their mercury levels can be 'normal'/low).