Maintaining QC Masks

A QC (quality control) mask is used to define the insertion of duplicate, replicate, blank, standard and spike QC samples into a stream of samples, using a rack layout mechanism, following the rules and definitions that are established for the tests in the laboratory.

QC Mask Scope

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

Properties of a QC Mask

A QC mask can have:

A container type—The rack or tray used to hold samples for a particular scheme, and defines the default rack size to be used in calculating QC placements.
Multiple QC mask placements—The position and name of any QC samples that are positioned in the rack when the QC mask is applied to a particular scheme. A QC mask placement specifies how duplicate, replicate, blank, standard and spike QC samples are placed within a stream of samples.

Use of QC Mask

QC samples are inserted into a group of samples that require analysis, to allow reliability, consistency and other quality metrics to be measured for the analytes that are active for QC assessment within a scheme.

QC masks are assigned to sample schemes, inherited from the scheme version, to control the insertion of QC samples within the analytical sample stream. QC masks allows the automatic placement of quality control samples, which assist in the quality control of analysis, into the physical racks that hold the samples for a job scheme, without the need to specify individual QC samples in the job. The analytical stream may be those sample schemes associated with a job scheme, or just those registered for a job scheme at a later time, or those being added to a laboratory batch job.

Samples in a production job can have an append or overwrite QC process run to add QC samples to the production job, and samples in a laboratory batch job can have an append QC process run to add QC samples to the laboratory batch job.

When a QC sample is created from a QC mask member placement, the sample's Primary Analytical Type and Primary QC Type Code are determined from the QC mask member's QC Type Code. The sample's Secondary Analytical Type and Secondary QC Type Code are determined from the QC mask member's Secondary QC Type Code. These two properties will fully define the type of QC assessment that is performed upon the QC sample.

Structure of a QC Mask

The purpose of a QC mask is to fix the placement and selection of QC samples when inserted, or appended, to the sample scheme stream. QC mask creation includes specifying the default rack size and QC placements.

Note: A duplicate and replicate QC mask member placements cannot exist in the same QC mask.

A QC mask with a duplicate QC mask member placement can only be attached to a scheme that has a Scheme Type of Sample Preparation. A QC mask with a replicate QC mask member placement can only be attached to a scheme that has a Scheme Type of Analytical Preparation or Analytical.

Default Rack Size

The QC mask application offers a great deal of flexibility. A default rack size can be applied to samples processed by a QC mask. This is done by selecting a Container Type for the QC mask, such that, the container type's Default Number of Containers becomes the rack size. For in-rack placements, the rack size is used as a placement cycle delimiter, and defaults the block size to the rack size. This default size can be subsequently adjusted by the operator.

QC Placements

Specify each QC mask member. Each QC mask member pertains to a placement that must be made into the sample group.

Example: Add two blanks to a rack, one as a reagent blank, and the other as an instrument rinse blank by defining two QC mask members.

Specifying a QC mask member involves the following steps:

Specifying a QC placement as either cross-rack or in-rack.
A cross-rack placement treats all samples in the scheme as though they are in one rack, that is, there is no resetting of the position of the next block based upon a rack delimiter.
An in-rack placement takes the rack size into consideration and distributes QC (and redistribute unknown samples) with strict adherence to block size.
All cross-rack placements are applied first during an update/overwrite QC process, followed by the in-rack placements.
Selection of samples for creating duplicate, replicate and spike QC samples, and the placement of standard or blank QC samples, can be associated with the rack structure (in-rack), or applied to the entire sample stream (cross-rack). For example, one blank at the start of the batch is an example of a cross-rack placement.
Specifying the primary analytical type and primary QC type of QC samples created by the QC placement.
When a new QC mask member is created, the first action is to select the Analytical Type and QC Type Code.
Any QC sample that is created by a QC mask member placement has its Primary Analytical Type and Primary QC Type set to the QC mask member's Analytical Type and QC Type Code, respectively. Refer to create a QC type for primary assessment. For the example, the Analytical Type is selected as BLANK and QC Type Code is selected as REAGENT_BLANK, or the Analytical Type is selected as BLANK and QC Type Code is selected as RINSE_BLANK.
Specify the source samples for duplication, replication and spiking.
If the QC mask member's Analytical Type is Duplicate, Replicate or Spike, then the Selection determines which sample is used as the original sample for duplication, replication or spiking.
The Selection Type limits the selection of the original sample to those samples in the incoming sample stream that have a specified Primary Analytical Type.
The Placement determines where the QC sample is placed in relation to the original sample, or rack boundary.
Specify the cycling of selections and placements.
Per Block is the size of the block of samples into which this QC mask member placement is made.
A selection and placement to create a duplicate, replicate or spike QC sample is made as long as the block contains the Minimum number of samples of the specified Selection Type. A placement to create a standard or blank QC sample is made as long as the block contains the Minimum number of unknown, duplicate, replicate or spike QC samples.
Specify whether multiple consecutive QC samples are to be placed.
To create a set of a QC samples, that is, where a number of QC samples of the same Analytical Type and QC Type are placed consecutively in the rack, the Number to Apply must be adjusted to a number greater than one.
The first and subsequent QC samples all have their Primary Analytical Type and Primary QC Type Code set to the QC mask member's Analytical Type and QC Type Code.
Specify whether multiple consecutive QC samples are to be linked as duplicate or replicate pairs.
When multiple consecutive QC samples are placed such that their is a first and subsequent QC samples that have the same Primary Analytical Type and Primary QC Type, the subsequent QC samples may be linked to the first QC sample to allow replicate or duplicate assessment between the pairs.
In this case, as long as the QC types are set up correctly, if a Secondary QC Type Code is selected, then the subsequent QC samples have their Secondary QC Type Code set to the QC mask member's Secondary QC Type Code, and have their Secondary Analytical Type set to the secondary QC type's Secondary Analytical Type.
Refer to create a QC type for secondary duplicate or replicate assessment.
For example, where a QC type with a Code of STD has an Analytical Type of Standard, and a QC type with a Code of STD_DUP has an Analytical Type of Standard, a Secondary Analytical Type of Replicate and a Linked QC Type Code of STD, and a QC mask member is created with its Analytical Type set to Standard, QC Type Code selected as STD, Number to Apply set to 2, and Secondary Analytical Type Code selected as STD_DUP, when the QC mask is applied, then two samples are created, such that, each sample has a Primary Analytical Type of Standard and a Primary QC Type Code of STD, but the second sample also has its Secondary Analytical Type set to Replicate and Secondary QC Type Code set to STD_DUP. Both samples undergo standard assessment, but the second sample also undergoes replicate assessment.
If a sample with secondary QC characteristics is added as a separate QC mask member, the sample is only assessed based upon its primary assessment characteristic.
Specify whether to propagate any QC samples created for a job scheme into sequel job schemes, based upon:
a) deemed precursor scheme relationships between sample preparation schemes and any analytical preparation or analytical scheme, and
b) actual precursor scheme relationships defined in the CCSCHM—Scheme application.
Precursor-sequel schemes relationships are used so that any QC sample that is registered for a precursor job scheme is propagated to, that is, registered for, a sequel job scheme.
Where the Propagate is selected, when a QC sample is created in a precursor job scheme, then it is propagated to any sequel job scheme and registered there also.
For example, a duplicate QC sample created for a sample preparation job scheme is propagated into a sequel analytical preparation or analytical scheme if the unknown sample is registered in those schemes. Similarly, a standard QC sample created in an analytical preparation job scheme is also created in a related analytical job scheme. A scheme that is set to inherit propagated QC samples may add its own QC distribution. This is overlaid onto the rack created by propagation and, for the purposes of QC insertion, the pre-propagated QC are considered as though they are unknown sample types. That is to say, their position in a rack is subservient to that of the incoming QC mask samples, but does not extend to them being selected for duplication or replication. Refer to maintain precursor schemes for a scheme.
Specify the standard material for blank, standard or spike QC placement.
A blank, standard or spike placement should be associated with either a Standard Code or Standard Group Code, although if initially left empty, this can be populated after the blank, standard or spike QC sample is created.
If the placement is associated with a standard group instead of with a standard, the standard is determined from the group at time of creating the QC sample.
The current lot number is determined from the standard also at time of creating the QC sample.

Previewing QC Masks

Once a QC mask is specified, it can be previewed in the context of a selectable number of samples so that you can see the typical placements that would be made, although if random selection is used, obviously this can vary. A preview can be used to check the QC mask configuration before it is applied to a job scheme in a job.

QC Mask Effect on the Process of Adding QC Samples to a Job

When an append QC process is applied to a job, QC samples are registered to the job based upon each sample scheme's QC Mask Code. Refer to Creating QC Samples using QC Masks.

Creation and Maintenance of QC Masks

QC masks are created and maintained using the CCQCMK—QC Mask application, which is also accessed using the Analysis Setup » QC Masks menu option.

Dependencies and Restrictions

QC masks created at organisation level can be used at laboratory level, but cannot be altered. QC masks can only be created for Analytical scheme types, and cannot be shared across scheme versions.