# What is and how to detect a dephased read

In the methods of this paper, the authors say:

To simplify analysis, we first removed any dephased reads in our library (last 6 bases of read did not match the expected sequence).

I have read this post and this one, and I think that a dephased read is one (according to the first paper) where the last 6 bases are not detected with good quality. In particular, I think this may be an example of a dephased read:

@...
CACACACACCAGTAAAAAANAGTTGCNNCNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
+
AAAAAEEAEEEEEEEEEE6#EAEEEE##E#####################################


where the quality of the read drops in the middle. Is that correct? If yes, should they be all of bad quality or at least one? And, if not, how can I detect a dephased read?