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Assessment method

Pathology laboratories enrolled in the scheme participate in an assessment run by staining slides circulated from NordiQC. The laboratories obtain unstained slides only after electronic submission of relevant protocols with the information requested in the form at www.nordiqc.org. Only one protocol is accepted for each epitope. If a laboratory submits a second protocol for a given epitope (e.g., because of corrections), it overwrites the first.


Only the stains listed at a particular run can be submitted for assessment. If a laboratory does not stock an antibody needed for the detection of an epitope, it cannot be replaced by another antibody. This is due to the design of multitissue blocks and the need for a large number of comparable stains in order to make a proper assessment. For the same reason, stains are not assessed if inappropriate antibodies have been used.


The sections circulated are serial sections cut from multitissue blocks containing several normal and tumour tissues. For each epitope two (and only two) unstained sections are sent to laboratories, which have submitted protocols before the announced deadline. Together with the slides, basic information (tissues included, deadline for submission etc.) is provided. Unstained slides are sent at the date indicated on the Participation page. Individual arrangement for obtaining slides is not possible. As for the first run in a fiscal year, an invoice is included.


Laboratories are requested to perform staining using their standard protocol. One (and only one) slide for each epitope should be submitted to NordiQC for assessment together with the in-house control slide. The other NordiQC slide should be kept in the laboratory as control. In case slides are broken at the receipt, NordiQC should be contacted by e-mail.


All stained NordiQC slides are assessed and marked by the assessor group. Generally, the assessment is based on the staining intensity and distribution in cells expected to stain, background staining, signs of cross-reactivity, counter-staining and tissue preservation during the staining process. Detailed criteria are indicated on the assessment page for each marker. The control stains are not assessed. However, they are requested in order to interpret insufficient stains and - in the future - also to guide the selcetion of controls. Slides submitted after deadline will also be assessed, but there may be some delay.


Provided the use of an appropriate antibody, each stain is marked as optimal, good, borderline or poor.

- Optimal staining: The staining is considered perfect or close to perfect in all of the included tissues.

- Good staining: The staining is considered fully acceptable in all of the included tissues. However, the protocol may be optimized to ensure the best staining intensity and signal-to-noise ratio.

- Borderline staining: The staining is considered insufficient, e.g., because of a generally too weak staining or a false negative staining of one of the included tissues, or a false positive staining reaction. The protocol should be optimized.

- Poor staining: The staining is considered very insufficient e.g., because of false negative staining of several of the included tissues, or a marked false positive staining reaction. An optimization of the protocol is urgently needed.

Moderate or strong false positive staining due to, e.g., endogenous biotin is not compatible with an optimal staining.


● The laboratory should compare their stains and protocols with the optimal stains and recommended protocols published at www.nordiqc.org. A protocol recommended by NordiQC as well as changes suggested by the assessment have to be tested carefully in the individual laboratory before implementation into the diagnostic work. NordiQC cannot take any responsibility for the consequences of changes in protocols or methods in a laboratory.


Examples of optimal and suboptimal staining results are uploaded on the website as of the date indicated on the Participation page. Among protocols giving an optimal staining, 2-4 are presented as recommended protocols. These are selected to reflect a spectrum of antibodies and methods and to represent different participating laboratories. The names and e-mail addresses of laboratories providing optimal protocols are given in the protocols to encourage direct communication between laboratories. If a participant providing a protocol wish to remain anonymous, this should be specified in the Comments field. Suboptimal stains are presented anonymously with indication of possible problems or errors in the protocols.


The core group informs all participants about their individual scores via e-mail.  In case of a borderline or poor staining result, suggestions for protocol optimization are given. In some cases comments are given also to good stains, e.g., in case of excessive counter-stain.


In case of borderline or poor marks, the laboratory may request a reassessment of either the original stain or a new stain: Two new unstained sections may - when available - be obtained from NordiQC for a new staining, e.g., after improvement of the protocol. To obtain new sections, the participant must fill out a new protocol form before deadline for the next run. In the form, select "Other epitope by appointment", specify the epitope, fill in protocol data, and write "Reassessment' in the Comments field. The new sections are sent together with the sections for the next run and the stains included for assessing at the assessor meeting.


Submitted stains (including control stains) are stored in the NordiQC file for future documentation. The laboratories may request the stains for review but they must be returned to NordiQC.



Last update 03-03-2008