How to pronounce HBsAg?

very carefully i imagine

aitch bee ess ay gee...

Thanks.

But can't Ag be read as "agg?"

i suppose, but abbreviations are usually pronounced one letter at a time...

No, it's pronounced as Region indicated.

I feel it is most convenient to just read it as "Hepatitis B surface antigen。"

Does Region indicated mean jargon？

You can read it that way if that's what you see in your mind's eye. The two are used (and spoken) interchangeably.

interesting.

in the context where I would normally see this combination of letters, I'd think someone was indicating that they had a Bachelor's of Science degree, with their Honours taken in Agriculture. I'd just think someone had put the H at the wrong end of the designation. B.S. Ag.(H)

I'd probably say the words to make sure people knew what I was trying to communicate.