# Taxonomy assignment with custom COI database - odd/wrong classifications?

**URL:** https://forum.qiime2.org/t/taxonomy-assignment-with-custom-coi-database-odd-wrong-classifications/19258
**Category:** Technical Support
**Tags:** taxonomy, feature-classifier
**Created:** [April 16, 2021, 9:38pm UTC](https://forum.qiime2.org/t/taxonomy-assignment-with-custom-coi-database-odd-wrong-classifications/19258 "2021-04-16T21:38:12Z")
**Posts on this page:** 1
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### Author: ![SoilRotifer](https://forum.qiime2.org/user_avatar/forum.qiime2.org/soilrotifer/32/21071_2.png) [@SoilRotifer](https://forum.qiime2.org/u/SoilRotifer)
#### Post date: [April 18, 2021, 9:51pm UTC](https://forum.qiime2.org/t/taxonomy-assignment-with-custom-coi-database-odd-wrong-classifications/19258/2 "2021-04-18T21:51:29Z")

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Hi @elaine-shen,

There could be a variety of reasons for this. Most common is inconsistent taxonomic annotations which 'confuse' the classifier...

I would suggest trying out the CO1 reference databases from @devonorourke:  
BOLD references:

> [@Building a COI database from BOLD references](https://forum.qiime2.org/t/building-a-coi-database-from-bold-references/16129):
>
> construction stop_signconstruction stop_signconstruction stop_signconstruction stop_signconstruction stop_signCitations: If you use the following COI resources or RESCRIPt for COI database preparation, please cite the following: Michael S Robeson II, Devon R O’Rourke, Benjamin D Kaehler, Michal Ziemski, Matthew R Dillon, Jeffrey T Foster, Nicholas A Bokulich. RESCRIPt: Reproducible sequence taxonomy reference database management for the masses. bioRxiv 2020.10.05.326504;…

The files are available here:

> [@Building a COI database from BOLD references](https://forum.qiime2.org/t/building-a-coi-database-from-bold-references/16129/37):
>
> Hi @smayne11, thanks for your question. I think you should give the ANML classifier a shot. I'd be curious to see how many of your sequence variants are classified (or unclassified), and among those with some taxonomic labels, what fraction are being assigned Family, Genus, or Species-level information. If the classifier isn't working for you and you want to generate your primer-specific classifier starting from the broader BOLD sequence and taxonomy files now hosted by QIIME2 here: [https://…](https://qiime2-data.s3-us-west-2.amazonaws.com/community-contributions-data-resources/2021.04-bold-resources/bold_anml_classifier.qza)

and the NCBI approach here:

> [@Building a COI database from NCBI references](https://forum.qiime2.org/t/building-a-coi-database-from-ncbi-references/16500):
>
> construction stop_signconstruction stop_signconstruction stop_signconstruction stop_signconstruction stop_signCitation: If you use the following COI resources or RESCRIPt for COI database preparation, please cite the following: Michael S Robeson II, Devon R O’Rourke, Benjamin D Kaehler, Michal Ziemski, Matthew R Dillon, Jeffrey T Foster, Nicholas A Bokulich. RESCRIPt: Reproducible sequence taxonomy reference database management for the masses. bioRxiv 2020.10.05.326504; d…

There is another CO1 reference database maintained by the Porter Lab available [here](https://github.com/terrimporter/CO1Classifier).

I think it would be a good to compare these reference databases to your existing one.

-Cheers!  
-Mike

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