# Option C: Pre-Built Reference Files

If you do not have matched normal samples available, Illumina provides pre-built systematic noise files as part of the DRAGEN Bio-IT Platform product files. These reference files can serve as a starting point for evaluation, but they are not optimized for your specific library prep kit, target panel, or sequencer combination.

## Considerations for Pre-Built Reference files

* Select a WES file if your panel targets only coding regions, or a WGS file if it includes non-coding regions.
* When possible, match the sample type to the sample type used to build the noise file. For example, if you have a Fresh Frozen (FF) sample use a reference file that comes from FF samples. If the reference file comes from a mix of Fresh Frozen and FFPE (FF/FFPE) samples it can be used with either.
  * The information about the DRAGEN pre-built noise files is in this link: [Pre-built resource files](https://help.dragen.illumina.com/dragen-v4.5/reference/resource-files/prebuilt-baseline-files)

## Where to Download

Pre-built noise files are available for download at the [DRAGEN Bio-IT Platform product files page](https://support.illumina.com/sequencing/sequencing_software/dragen-bio-it-platform/product_files.html).

{% hint style="warning" %}
**IMPORTANT.** Using pre-built reference noise files will result in **lower filtering performance** compared to a noise baseline built from your own matched normal samples. This option is provided as a fallback for initial evaluation only. For production use, generate a custom noise file with [Option A](/dragen-somatic-for-idt-custom-panels/stage-1-generate-systematic-noise-file/option-a-run-planner.md) or [Option B](/dragen-somatic-for-idt-custom-panels/stage-1-generate-systematic-noise-file/option-b-bssh-ica.md).
{% endhint %}


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