# Monitor biomarker positivity rates across labs in real time to catch assay drift

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

## TL;DR

If one lab suddenly reports twice the rate of 'positive' biomarker results that other labs report, its assay has probably drifted. Pooling anonymised positivity rates by laboratory, assay and version, with automated outlier detection and case-mix adjustment, would catch reagent lot problems and protocol drift within weeks rather than at occasional proficiency runs.

## Summary

Statistical process control on population-level positivity rates is standard in clinical chemistry and screening programmes but not in predictive oncology biomarkers. A national feed of anonymised biomarker results by laboratory, assay and version, with automated outlier detection and case-mix adjustment, would detect reagent lot problems, protocol drift and algorithm changes within weeks rather than through occasional proficiency runs.

## Fields

- Kind: Idea
- Last checked: 2026-09-08
- Hypothesis: Surveillance will identify at least two laboratory-level drift events per year in a national system, each confirmed on re-testing, that proficiency schemes had not detected.
- Rationale: Screening programmes detect reader drift through recall-rate monitoring; the same logic applies to any test with a stable expected positivity rate.
- Proposed test: Pilot with PD-L1 and HER2 results from 30 laboratories over one year; investigate flagged outliers with sample re-testing.
- Maturity: speculative
- Actor: data

## 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

- ideas: [Publish each laboratory's biomarker proficiency results](https://onco.cc/ideas/idea-tr2-eqa-public-results/), [Version control and locked reference sets for AI algorithms used as companion diagnostics](https://onco.cc/ideas/idea-tr2-ai-cdx-change-control/)
- technologies: [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/)
- bottlenecks: [Biomarkers are not validated or standardised](https://onco.cc/bottlenecks/b-biomarker-validation/), [Data silos](https://onco.cc/bottlenecks/b-data-silos/)
- key papers: [Examination of Low ERBB2 Protein Expression in Breast Cancer Tissue](https://onco.cc/key-papers/paper-fernandez-jama-oncol/)

---
JSON: https://onco.cc/api/v1/entities/idea-tr2-positivity-rate-surveillance.json