# Condition for concordance correlation coefficient equals -1

Lin's concordance correlation coefficient (CCC) which is used to quantify the extent of agreement between two measures ranges between [-1,1]. I want to know under what condition does perfect discordance ($$CCC=-1$$) hold true? Based on my thinking and reasoning, I had few doubts which I would like to clarify:

1. Is this only possible when means of two variables equals 0, variances of two variables is identical and $$PCC=-1$$?

2. Is there any other possibility when $$CCC=-1$$ apart from 1.?