# One digital PD-L1 scale that maps across all the competing assays

Source: https://onco.cc/ideas/idea-tr2-pdl1-digital-calibration/  
OnCo record `idea-tr2-pdl1-digital-calibration` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

There are several different PD-L1 tests, each tied to a different drug, and they disagree. A single digitally calibrated scale would let any lab's result be translated into any drug's cut-off.

## Summary

22C3, SP263, 28-8 and SP142 assays, with tumour proportion score, combined positive score and immune-cell scoring, produce different positivity for the same tumour. The Blueprint project showed partial concordance. A quantitative digital pathology reference (stain intensity and cell counts calibrated on shared reference materials) could express each assay on a common scale, so a lab running one assay could report validated equivalents for the cut-offs used in each drug label.

## Fields

- Kind: Idea
- Last checked: 2026-09-08
- Hypothesis: A calibrated digital PD-L1 score will predict benefit from PD-1 blockade at least as well as each label-specified assay in retrospective analyses of trial samples, allowing a single test to serve multiple drugs.
- Rationale: Digital quantification removes reader variability, and reference materials remove staining variability, the two dominant sources of disagreement.
- Proposed test: Stain trial samples from two registrational immunotherapy trials with all four assays plus the digital scale; compare predictive performance against outcomes.
- Maturity: early-clinical
- Actor: research

## Sources

- Bottleneck evidence (Biomarkers are not validated or standardised): Fernandez et al., Examination of low ERBB2 protein expression in breast cancer tissue (JAMA Oncology 2022): https://doi.org/10.1001/jamaoncol.2021.7239

## Connected records

- companies: [Paige AI](https://onco.cc/companies/paige/), [PathAI](https://onco.cc/companies/pathai/)
- technologies: [Digital pathology & AI](https://onco.cc/technologies/digital-pathology-ai/), [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/), [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/)
- targets: [PD-L1](https://onco.cc/targets/pdl1/)
- drugs: [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/)
- bottlenecks: [Biomarkers are not validated or standardised](https://onco.cc/bottlenecks/b-biomarker-validation/), [No one can predict who responds to immunotherapy](https://onco.cc/bottlenecks/b-immunotherapy-response/)
- key papers: [Examination of Low ERBB2 Protein Expression in Breast Cancer Tissue](https://onco.cc/key-papers/paper-fernandez-jama-oncol/)
- ideas: [Drug labels must state which biomarker assays were validated and how they compare](https://onco.cc/ideas/idea-tr2-label-assay-concordance/), [Public gold-standard datasets for validating every cancer biomarker test](https://onco.cc/ideas/idea-tr2-open-cdx-validation-sets/)

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