Hi, my category is IR2 and I have already gone to the interview before.
At the interview, I received a 221g requesting a DNA test be done to confirm paternity because my birth cert. doesn't have my petitioner's name - we did that and now the Embassy has the result.
Now, they've sent me a letter (another 221g) telling me to send my passport through LBC. (Perhaps no more 2nd interview, so I can't bring my passport to the Embassy anymore.)
DNA was positive, so I'm guessing they want my passport for stamping.