Maintaining QC Standards

• Maintaining QC Standards
  • QC Standard Scope
  • Properties of a QC Standard
  • Use of QC Standards
  • Standard Status
  • Standard Specifications
  • Creation of Standards
  • Allowing Standards as Spikes
  • Types of Samples that Link to Standards

A standard, also known as a quality control (QC) standard, is a substance of known quality.

QC Standard Scope

QC standards are created either with org-scope or lab-scope. An organisation or laboratory can contain multiple standards.

QC standards are classified by type:

• Blank—A substance with no determinable amount of a specific material, used to create a blank QC sample, for determining background factors in a testing environment or instrument.
• Standard—A substance with a known amount of specific material, used to create a standard QC sample, for calibrating a testing environment or instrument.
• Spike—A substance with a known amount of specific material added to an unknown sample to create a spike QC sample, for establishing a testing matrix.

Properties of a QC Standard

A QC standard can have:

• Multiple standard lots—Each standard lot links to a standard specification. QC materials rely on a standard specification to dictate the limits of acceptability for any particular scheme, or analytical instrument. It is the adherence to these prescribed limits that allows a batch of results to be reported confidently to the customer.
• Multiple hazards—Labels can be configured to contain hazard warnings for standards.
• An evaluation script—Used for custom assessment.
• Reporting details, including a pass, warning and failure statement.

Relative values can be entered, but these are converted to and persisted as absolute limits.

Use of QC Standards

A sample can be created as a blank QC sample, standard QC sample or spike QC sample, and linked to a QC standard and its current standard lot, which, in turn, links to a standard specification. Then the QC sample's results are assessed against the limits for the standard specification.

QC standards can be made members of various standard groups to assist with assigning standards to blank, standard and spike QC samples created from QC mask members.

Standard lots allow for batch variation in QC materials. Batch variance may not be an issue with certified reference materials but can be significant where standard materials are created in-house or where supplier may vary over time. The standard and standard lot hierarchy allows a specification to be adjusted without causing a disturbance to historical data for a particular material since the specification is a property of the standard lot.

Standard Status

Standards and standard lots have a tri-state activity statuses:

• Draft
• Active
• Suspended.

The flows are:

• Activate: Draft --> Active or Suspended --> Active
• Deactivate: Active --> Draft
• Suspend: Active --> Suspended.

The difference between a draft and suspended standard is minor: both states prohibit the selection of the standard or associated standard lot on a drop-down choice. However, suspension implies the standard or standard lot was previously active and now should NOT be used, whereas draft implies that the standard or standard lot is still undergoing checking and validation processes so is not yet ready for use by the laboratory. This only can occur after activation.

When deactivating or suspending a standard or standard lot, the user is given the option to enter a reason as to why the action is being performed.

Standard Specifications

Specifications are created for standard lots, to apply sets of warning and failure limits (QC limits) to the QC samples created from the standard lot. These limits are initially calculated according to the statistical detection limit and repeatability of the scheme version analytes (SVAs).

Where a standard lot is linked to a standard specification, when the standard and its current standard lot is applied to a blank, standard or spike sample, then the sample is linked to the standard specification.

Then when a result is received for the sample, the result is assessed against the limits for the MATCHING SAMPLE SCHEME ANALYTE UNIT in the standard specification on the sample to determine whether they fall within the expected range, and to set the sample scheme analyte's Standard Status. This status rolls into the sample scheme analyte's Composite QC Status.

The STANDARD_AUTO_CREATE_LOT_AND_SPEC application preference is used to create a standard lot and its specification automatically when a standard is created, and link it automatically to the standard lot.

Creation of Standards

Every time a standard is created, a standard lot and a specification associated with the standard lot are created automatically if permitted by the preferences that are set up at configuration. The newly created standard lot displays in the drop down list for Current Standard Lot Number, and the standard lot's specification displays in Specification Code column of the Lot Specifications tab.

When a new standard is created, the standard, and any standard Lot and associated specification that were created automatically, are activated automatically. You can suspend or deactivate a standard lot using the Suspend or Deactivate buttons.

Laboratory administrators or managers can mark a standard as approved for export, so that it is available for importing into other organisations. Organisational administrators can then approve those finalised standards to be used by their laboratories so that all the standards are standardised globally.

Allowing Standards as Spikes

If the ALLOW_STANDARDS_AS_SPIKES application preference is:

• Checked, then a QC mask placement can be associated with a standard that has a Standard Type of Standard or Spike, and a spike QC sample can be associated with a standard that has a Standard Type of Standard or Spike.
• Unchecked, then a QC mask placement can only be associated with a standard that has a Standard Type of Spike, and a spike QC sample can only be associated with a standard that has a Standard Type of Spike.

Types of Samples that Link to Standards

Samples that have a Primary Analytical Type or Secondary Analytical Type of Blank, Standard or Spike need to link to a standard, standard lot and standard specification for standard assessment to take place after result entry, to set the sample scheme analyte's Standard Status, which then rolls up into the sample scheme analyte's Composite QC Status.