# 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.

DNA library QC results are available in the `MetricsOutput.tsv` file. Refer to [Metrics Output ](https://help.tso500software.illumina.com/dragen-tso-500-ctdna-guides/dragen-tso-500-ctdna-v2.6/analysis-output/metrics-output)for details.

| Metric                          | Description                                                       | Recommended Guideline Quality Threshold | Variant Class                   |
| ------------------------------- | ----------------------------------------------------------------- | --------------------------------------- | ------------------------------- |
| CONTAMINATION\_SCORE            | The contamination score is based on VAF distribution of SNPs.     | ≤ 1227                                  | All                             |
| MEDIAN\_EXON\_COVERAGE          | Median exon fragment coverage across all exon bases.              | ≥ 1300                                  | Small variant, TMB, Fusion, MSI |
| PCT\_EXON\_1000X                | Percent exon bases with 1000x fragment coverage.                  | ≥ 80.0                                  | Small variant, TMB              |
| GENE\_SCALED\_MAD               | The median of absolute deviations normalized by gene fold change. | ≤ 0.059\*                               | CNV                             |
| MEDIAN\_BIN\_COUNT\_CNV\_TARGET | The median raw bin count per CNV target.                          | ≥ 6.0                                   | CNV                             |