# Freeze thaw stability of TruSight Oncology 500 (TSO500) ctDNA (v1 and v2) input and reagents

**Will repeated freeze-thaw cycles will impact the cfDNA/ctDNA quantity and impact assay performance?**\
Illumina has not tested repeated freeze thaws of cfDNA samples. In general, it is important to limit the number of freeze thaws for cfDNA/ctDNA and commercial control samples, and this must be validated by each lab according to the samples used and sample handling workflows. Repeated freeze-thaw cycles may impact input quality and, therefore, quantity that can be converted to library.

**How many freeze-thaw cycles are supported for kit reagents?**

For the version 1 kit: Eight freeze-thaw cycles are supported.

For the version 2 kit: Six freeze-thaw cycles are supported.

**Note**: Several reagents included in each kit version are supplied in multiple tubes, allowing for limited freeze-thaw cycles depending on library preparation batch sizes.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #2919), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000002919%20-%20Library%20Preparation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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