Can i attend Tier 2 Visa interview by providing IELTS reference No in visa application?

Hi ,
I haveMasters of education ,Masters degree completed from USA in 2010, do I still need to prove my English language proficiency for UK immigration by writing IELTS or do I need to get certificate from UK NARIC that it's equivalent to UK degree standards or shall I apply for tier 2 visa directly with USA Masters degree certificate.

Can i attend tier 2 visa interview by just providing IETLS reference no in the application form, as my report takes 10 more days to publish in online and Hard copy certificate takes 15 more days to reach me.