Quality Control

The software calculates several quality control metrics for runs and samples.

Run QC

The Run Metrics section of the metrics output report provides sequencing run quality metrics along with suggested values to determine if they are within an acceptable range. The overall percentage of reads passing filter is compared to a minimum threshold. For Read 1 and Read 2, the average percentage of bases ≥ Q30, which gives a prediction of the probability of an incorrect base call (Q‑score), are also compared to a minimum threshold. The following tables show run metric and quality threshold information for different systems.

The values in the Run Metrics section are listed as NA in the following situations:

• If the analysis was started from FASTQ files.

• If the analysis was started from BCL files and the InterOp files are missing or corrupt.

NextSeq 500/550 or NextSeq 550Dx (RUO)

NovaSeq 6000 or NovaSeq 6000Dx (RUO)

NextSeq 1000/2000

NovaSeq X

DNA Sample QC

DRAGEN TruSight Oncology 500 uses QC metrics to assess the validity of analysis for DNA libraries that pass contamination quality control. If the library fails one or more quality metrics, then the corresponding variant type or biomarker is not reported, and the associated QC category in the report header displays FAIL. Additionally, a companion diagnostic result may not be available if it relies on QC passing for one or more of the following QC categories.

DNA library QC results are available in the MetricsOutput.tsv file. Refer to Metrics Output for details.

RNA Sample QC

The input for RNA Library QC is RNA alignment. Metrics and guideline thresholds can be found in the MetricsOutput.tsv file. Refer to Metrics Output for details.

• To avoid failing RNA samples unnecessarily, Illumina does not recommend a universal threshold to determine RNA sample quality. RNA expression varies significantly across tissue types and a small panel size (55 genes), which makes normalization challenging. Tissue-specific thresholds could be considered for normalization.