Long 1st ed Earthdawn gamemaster here - my understanding of the Immortal Elves in earthdawn at least was that they were the elven children of one of the Great Dragons. There is a document released by FASA as they desolved, that had rules and hints on this, called Dragons. In this each elf gained a +1 to Willpower (actual and potential), gained Astral Perception/Sight and one "draconian" trait. Pointed Ears, slit pupils, etc.
The Exiled One among the Great dragons is a repeat practitioner of breeding metahuman/dragon hybrids.
So this may not be true in SR, I could have miss read things, but this means that a genetic test may reveal Draconian DNA, as well as the ability to demonstrate a draconian trait or aspect to their aura. Also determining your paternity/maternity among the living IEs may be all they are "testing"