Interobserver Reliability of Programmed Cell Death Ligand-1 Scoring Using the VENTANA PD-L1 (SP263) Assay in NSCLC

J Thorac Oncol. 2020 Apr;15(4):550-555. doi: 10.1016/j.jtho.2019.11.010. Epub 2019 Nov 25.


Introduction: The VENTANA PD-L1 (SP263) Assay is approved for use with anti-programmed cell death-1/programmed cell death ligand-1 (PD-1/PD-L1) therapies in NSCLC and urothelial carcinoma. Here, we investigate interobserver reliability of the SP263 assay, applied to PD-L1 scoring of tumor cells (TCs) in NSCLC.

Methods: Six practicing European pulmonary pathologists independently scored the proportion of TCs expressing PD-L1 (TC score) from 200 archival, commercially sourced, formalin-fixed paraffin-embedded NSCLC resections stained using the SP263 assay. Agreement in scores was analyzed using the intraclass correlation coefficient and concordance in patient's classification using Fleiss' kappa.

Results: Results from 172 samples showed strong pair-wise correlations between pathologists (R2 >0.89) for TC scoring with an intraclass correlation coefficient of 0.96. Overall agreement was greater than 90% for TC of 1% and above, and greater than 94% for TCs of at least 25% and at least 50%. Fleiss' kappa showed substantial agreement for TC of 1% and above, and almost perfect agreement for TCs of at least 25% and at least 50%.

Conclusions: Assessment of TC score in NSCLC was highly reproducible using the SP263 assay, building confidence in the accuracy of this assay in selection of patients for anti-PD-1/PD-L1 therapy.

Keywords: Assay reliability; Immunohistochemistry; Interobserver concordance; Programmed cell death ligand-1; SP263.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis
  • B7-H1 Antigen*
  • Humans
  • Immunohistochemistry
  • Ligands
  • Lung Neoplasms*
  • Reproducibility of Results


  • B7-H1 Antigen
  • Ligands