Check out this article (re one of the IVIG brands, Privigen). http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2697917/#!po=10.7843
I'm sure you can find something in the article re IgG numbers that justifies IVIG therapy.
Find out which IVIG therapy is offered by the doctor and research it backward and forward. I'm certain you'll find a nugget to help your fight.