# Setting QC Flags

In QC steps, some items have a QC flag associated with them. This flag can be read and set from script expressions. The value may be set to true or false.

Example expressions:

{% code overflow="wrap" %}

```markup
-exp 'input.QC = input.::Concentration:: >= step.::minConcentration:: && input.::Concentration:: <= step.::maxConcentration::' -exp 'output.QC = input.QC'-exp 'if(Step.::Concentration:: >= 1) { input.QC = true } else { input.QC = false }'
```

{% endcode %}


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