PT  - JOURNAL ARTICLE
AU  - Batenchuk, Cory
AU  - Albitar, Maher
AU  - Zerba, Kim
AU  - Sudarsanam, Sucha
AU  - Chizhevsky, Vladislav
AU  - Jin, Chelsea
AU  - Burns, Virginia
TI  - A real-world, comparative study of FDA-approved diagnostic assays PD-L1 IHC 28-8 and 22C3 in lung cancer and other malignancies
AID  - 10.1136/jclinpath-2018-205362
DP  - 2018 Dec 01
TA  - Journal of Clinical Pathology
PG  - 1078--1083
VI  - 71
IP  - 12
4099  - http://jcp.bmj.com/content/71/12/1078.short
4100  - http://jcp.bmj.com/content/71/12/1078.full
SO  - J Clin Pathol2018 Dec 01; 71
AB  - Aims At the time of analysis, two widely used, drug-specific, tumour-cell programmed death ligand 1 (PD-L1) assays were approved by the US Food and Drug Administration for anti-PD-1 therapies: the Dako PD-L1 immunohistochemistry (IHC) 28-8 pharmDx assay and the Dako PD-L1 IHC 22C3 pharmDx assay. Given that the majority of current PD-L1 testing in US clinical practice is performed at commercial reference laboratories, we aimed to evaluate the concordance of the 28-8 and 22C3 assays in a real-world setting.Methods Matched PD-L1 IHC 28-8 and 22C3 results from routine assessment were obtained from 1930 patients, including 412 confirmed to have lung cancer, submitted from hospitals in over 38 US states/territories. Biopsies were stained, reviewed and scored by trained/certified pathologists at a single cancer reference laboratory between 2015 and 2017. Rate of concordance between assay findings was assessed by Bland-Altman analysis; overall per cent agreement (OPA), positive per cent agreement and negative per cent agreement; and Cohen’s kappa.Results PD-L1 IHC 28-8 and 22C3 displayed strong correlation across all samples and in samples with a confirmed lung cancer diagnosis irrespective of biopsy site. The OPA was 97%–98% for all samples, depending on the expression level defining PD-L1 positivity. In the Bland-Altman analysis, the mean difference in percentage of tumour cells positively stained for PD-L1 between the paired assay findings was –0.80% for all samples and –0.93% in samples with a confirmed lung cancer diagnosis.Conclusions These data, in conjunction with recent findings, support the analytical concordance of the PD-L1 IHC 28-8 and 22C3 assays for assessing per cent tumour-cell membrane PD-L1 expression.