G0461 X 2 - 59 modifier used?

When we have two specimens and an immuno is done on each, we can code G0461 for each specimen. Do you code this as:

G0461 X 2

or

G0461

G0461 -59

I do coding, not billing. I have not been using a 59 modifier on the second G0461 and have not heard of any denials from our billing office. But, the question was raised today which is correct.

Thanks!

G0461 X 2 - 59 modifier used?