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Verification and validation of the anti-PD-L1 antibody, Clone 22C3 on a laboratory-developed test
  1. Shane Brennan1,
  2. Julie O'Neill1,
  3. Susan Kennedy1,2
  1. 1 Pathology, Saint Vincent's, Dublin, Ireland
  2. 2 Pathology, Royal Victoria Eye and Ear Hospital, Dublin, Ireland
  1. Correspondence to Dr Shane Brennan, Pathology, Saint Vincent's, Dublin 4, Ireland; brennanshane1{at}


Aims The first aim of this study is to compare and validate the performance of the programmed death receptor ligand 1 (PD-L1) IHC 22C3 pharmDx assay kit processed via Dako Omnis platform with the Dako Autostainer Link 48. The second aim is to examine the concordance of scoring by pathologists using the same immunohistochemistry (IHC) assay on the Dako Omnis platform and the Dako Autostainer Link 48.

Methods Fourty-seven formalin-fixed, paraffin-embedded tissue blocks of head and neck squamous cell carcinoma tumour were stained with the PD-L1 IHC 22C3 pharmDx assay kit processed via the Dako Autostainer Link 48 and the Dako Omnis platform. Combined positive score (CPS) was ascribed by two scoring pathologists, with discordant cases provided with an agreed score.

Results First, identical staining patterns were identified. Second, high agreement of PD-L1 scores when a CPS cut-off of 1 was implemented illustrated an overall agreement of 94%, positive agreement of 100% and negative agreement of 88%. Finally, results highlight an intraexaminer concordance of 89% and interexaminer concordance of 85% and 92%.

Conclusions In conclusion, we propose to open for discussion the deconstruction of the current practice of a compulsory companion diagnostic test (CDT) for a particular PD-L1 immunohistochemical assay. The implementation of laboratory developed tests as an alternative to the CDT poses as a novel and readily available method to surmount limitations posed to pathology laboratories.

  • Pathology, Molecular
  • Pathology, Oral
  • Pathology, Surgical
  • Head and Neck Neoplasms

Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.

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Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.

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  • Handling editor Runjan Chetty.

  • Contributors Conceptualisation: SK. Methodology: JON conducted the laboratory analysis on selected slides reviewed by SB/SK. SK/SB conducted quality analysis of the staining and scoring. Results: assimilation and interpretation conducted by SK/SB. Writing: SK and SB. SK is the guarantor.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.