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Quality Assurance Unit - Scheme Details

PT Number
Scheme title
Scheme outline for IHC

There will be 6 rounds of assessment per annum. In each round participants will be requested to perform two specialised immunohistochemistry methods. Participants will normally be issued with two unstained paraffin sections per method. One of these slides per method should be returned by the participants for assessment along with a self-provided in-house control slide for each requested immunohistochemistry method.

Each batch of slides issued is quality control checked to ensure that all slides issued are homogeneous within the batch. The period covering the distribution has been included when the expiry dates of samples were determined.


It is important to not remove or obscure the original identification system on the self-provided in-house control slide labels. After receipt the participantís lab identity system will be made anonymous by covering over with removable adhesive labels.

Information requested

Details of methods and/or reagents used should be recorded on the result entry sheets. This enables the provision of useful feedback from assessors to participants. This information is not assessed and will not appear on the final report.  


The assessment of submissions is designed to be as fair and consistent as possible. The assessment process is subcontracted to personnel who are qualified and well-practised assessors in techniques of Veterinary Immunohistochemistry. During assessment scores will be allocated to various criteria based on the quality of results in certain immunohistochemistry techniques and final scores will be awarded once the assessments are completed.


Reports are issued electronically, these will include: 

  • a summary of results for each technique
  • participant's scores
  • the overall mean and a histogram of overall scores
  • digital images of selected examples accompanied by comments provided by the Assessors.
Participants with restricted repertoires

The participant is responsible for communicating via the reporting form whether an immunohistochemical technique is part of their repertoire.

When a technique is not part of a participant’s repertoire, this will be classified as such and will not be assessed or scored.

Participants who fail to submit a slide tested for an immunohistochemical technique that is part of their declared repertoire will be classed as a non submission.

Each distribution will request two immunohistochemistry techniques from any of those listed below

Smooth Muscle Actin (Alpha)
Endothelial marker (of choice)
Macrophage Marker
Mast Cell Marker
Melanoma marker (of choice)
Pan B Cell marker (of choice)
Pan Cytokeratin
Pan T Cell marker (CD3)
Plasma cell marker (of choice)
Proliferation marker

Where it is the participant's laboratory’s policy to refer immunohistochemical techniques or slides to another department or laboratory, these should be included in the declared repertoire and the PT material referred to the relevant third party as if it were diagnostic material.

The department’s original submission material will be returned.

Performance monitoring

Good performance in one category cannot be offset against substandard performance in another.

The scheme organisers will not monitor substandard performance. This should be arranged by the participantís themselves and any subsequent investigations dealt with accordingly. However, participants are welcome to contact the scheme organiser or assessor for advice on such matters.

Poor performance is considered to be defined by receiving a score of 2 or lower.

Appeals procedure

Participants who are dissatisfied with any of their scores received can re-submit the slides to be re-assessed. These slides will be reassessed at the next scheduled round of assessment after receipt.
The participant should initially contact the scheme organiser and then return the slides for reassessment.

Any returned slides will be added to the list of the next round of assessment. After reassessment the slides will be returned to the participant.

The appeals procedure will remain confidential.

Slides are to be returned within

21 days

Sample type

Unstained paraffin sections of animal tissue.

Packaging and transport details

Transfer may be provided by normal post or Courier. Courier delivery will incur additional charges. Please contact the QA unit (VETQAS) for further details.

Participants are liable for the cost of return postage.

It is advisable that participants record receipt and dispatch of all PT materials.

When using plastic slide mailers, please take particular care when packing to protect the slides from movement such as filling any upper vacant space with padding. Also, seal the lid onto the container with adhesive tape to avoid spillage and breakage.

Number of distributions per year:



Various aspects of the Proficiency testing schemes may at times be subcontracted. When this occurs it is placed with a competent subcontractor and the Quality Assurance Unit is responsible to the scheme participants for the subcontractors work.

Date scheme started:


Accreditation Status:

ISO/IEC 17043: 2010 Conformity assessment Ė General requirements for proficiency testing.


(Alpha) Smooth Muscle Actin
A multi-block may be presented containing the following tissue: normal small intestine, gastrointestinal stromal tumour (GIST) and normal liver.
There should be intense labelling of the smooth muscle layers in the muscularis mucosae, including the fine actin filaments within the villus region, moderate to strong labelling of all the myofibroblasts, moderate to strong, labelling of the neoplastic cells in the GIST and strong labelling of all smooth muscle in any surrounding vessels. In the liver the majority of the perisinusoidal cells must show an at least weak to moderate labelling. Labelling should remain cytoplasmic in nature.
Calcitonin/Calcitonin Receptor
The tissue provided is usually medullary thyroid carcinoma.
Strong to medium labelling of the tumour cells.
The tissue could be pancreas, adrenal and/or small intestine.
We expect to see to see strong dark labelling within the neuroendocrine cells within the intestinal mucosa. However to test the sensitivity of participant’s methodology there should also be least some weak to moderate labelling of the nerve cell process within the outer muscular layers of the intestine as the expression of chromogranin in these cells although present is in lower levels.
The tissue provided is usually that of a Gastrointestinal stromal tumour (GIST), and expected results are strong to moderate staining of all the tumour cells.
The tissue provided is usually infected with feline infectious peritonitis (FIP).
Successful coronavirus immunolabelling should demonstrate medium to strong labelling within macrophages containing the virus and is characterised by numerous distinct intracytoplasmic granules.
The tissue provided is usually colon.
The smooth muscle cells should be well labelled with strong labelling of the muscularis mucosae and muscularis propria. There should also be a moderate to strong labelling of the majority of smooth muscle cells in the vessels. No reaction must be seen in the epithelial cells.
The tissue provided is usually normal skin and/or liver. There should be strong labelling of the cell junctions in the skin epithelium and a moderate to weak staining in all the cell junctions between the hepatocytes.
Endothelial marker
The antibody chosen should specifically react with the cytoplasm of endothelial cells from normal and neoplastic blood vessels and from lymphatic vessels. It also reacts with endocardium, platelets and megakaryocytes.
At all times the background should be clear.
The tissue provided is CNS.
In the CNS the anti-GFAP should label astrocytes and some ependymal cells. In the PNS Schwann cells, satellite cells and enteric glial cells are labelled.
At all times the background should be clear.
Macrophage Marker
The tissue provided could be liver and/or spleen.
There should be moderate to strong labelling of the hepatic Kupffer cells in the liver and strong cytoplasmic labelling of the macrophages in the red pulp and marginal regions of the spleen. There should be no labelling of the liver hepatocytes or the T or B cell populations in the spleen.
Mast Cell Marker
The tissue provided is mast cell tumour.
There should be strong predominantly membranous labelling of the mast cells with negative labelling of all other cells.
The tissue provided is from an amelanotic melanoma.
There should be moderate to strong, distinct cytoplasmic labelling of the majority of the neoplastic cells with no background labelling.
Pan B cells
The tissue provided is usually normal lymph node.
There should be strong labelling of the mantle zone B-cells, the germinal centre B-cells and the interfollicular B-cells in the lymph node. Other cells should remain negative.
Pan Cytokeratin
The tissue provided could be liver, oesophagus and/or colon.
In the liver the bile duct epithelium should be strongly labelled with the majority of hepatocytes moderate to strongly labelled, particularly the hepatocyte membrane.
There should be a strong distinct cytoplasmic labelling of the squamous epithelial cells in the oesophagus and of the simple columnar cells in the colon.
Pan T Cell (CD3)
The multi block presented contains normal canine lymph node, a lymphoma of canine intestinal origin with a scattered population of T cells and normal equine colon.
There should be strong sharp labelling of both normal and neoplastic T cells mostly present in surface membranes.
In the lymph node there should be moderate to strong labelling of all T cells within the interfollicular T zones as well as the small numbers present in the germinal centres.
All the T cells should be moderately to strongly labelled in the colon mucosa.
There should be moderate to strong labelling of the scattered population of T cells within the B cell lymphoma with no labelling of other cells present particularly the large population of B cells present.
Plasma Cell Marker
The tissue provided is a plasmacytoma and tonsil.
The antibody used should be able to demonstrate normal and neoplastic plasma cells. Depending on the antibody used, a subset of B-cells in the light zone of the germinal centre should be labelled, along with plasma cells, activated T-cells and a wide spectrum of related hematolymphoid neoplasms derived from these cells.
Proliferation Marker
The multi-block supplied contains the following tissues: normal lymph node and ileum which has a proliferative disorder.
Participants should obtain strong sharp nuclear labelling of the majority of germinal centre B lymphocytes in the lymph node and strong labelling of the majority of nuclei in the proliferating glands and crypt base.
The tissue provided is colon and pancreas.
Moderate to strong positive labelling should be observed in Schwann and glial cells in the colon and pancreatic islet cells. Labelling should demonstrate a strong clear nuclear and cytoplasmic pattern. Other cell types should be clean.
The tissue provided is adrenal and colon.
Laboratories are expected to demonstrate the presence of synaptophysin in the adrenal medulla with medium to strong labelling in the adrenal medullary cells with no background or non-specific labelling of the other cell types.  In the colon there should be strong labelling of all the axons and plexus present, along with a moderate to strong labelling of the endocrine cells of the mucosa.
The tissue provided is tonsil.
There should be a moderate to strong cytoplasmic labelling of all all the peripheral B- and T-cells must with no labelling in the surface squamous epithelial cells.

In all of the above, section quality should not impair the result.

For price and details of annual distributions please see price list or contact:
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