# Dada2: losing reads during merging

**URL:** https://forum.qiime2.org/t/dada2-losing-reads-during-merging/11487
**Category:** User Support
**Created:** [September 12, 2019, 3:14pm UTC](https://forum.qiime2.org/t/dada2-losing-reads-during-merging/11487 "2019-09-12T15:14:36Z")
**Posts on this page:** 1
**Showing post:** 10

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### Author: ![Jess\_Mackay](https://forum.qiime2.org/user_avatar/forum.qiime2.org/jess_mackay/32/5070_2.png) [@Jess\_Mackay](https://forum.qiime2.org/u/Jess_Mackay)
#### Post date: [September 13, 2019, 4:47pm UTC](https://forum.qiime2.org/t/dada2-losing-reads-during-merging/11487/10 "2019-09-13T16:47:32Z")

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I'm not sure about this. I know that the --p-trunc-q parameter (with a default of 2) truncates reads with low quality sequences. But it says in the documentation that "If the resulting read is then shorter than 'trunc-len-f' or 'trunc-len-r' (depending on the direction of the read) it is discarded." So the read would not end up too short, it would just be discarded, in which case I would see the loss of reads in the filtered column of the dns.

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