Same thing happened to me when I was referred to a allergist by my primary care doctor. The test itself was 600.00.
My Insurer refused to pay at first, saying it wasn't covered. Then they said the allergist wasn't part of the network and
he wasn't covered.
In the end my Insurer paid all of the bill when I reminded them that THEY were the ones who referred me to the specialist. (an error on their part)
I hate dealing with Insurance companies.