siga = Secretory SIgA Level.

A saliva test is used. It's needed in the immune system to fight off microorganisms, viruses and bacteria. A low level of it suggests adrenal exhaustion, so an adrenal stress index test would probably be the next step after that. A friendly bacteria with a weird name, something Boulardii can be used to raise the SIga Level. Not that i have tried this, but i know a therapist who looks at this area first in a patient.