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Diagnostic Accuracy in Fit-for-Purpose PD-L1 Testing

Carol C Cheung1,2, Hyun J Lim3, John Garratt4

  • 1Department of Pathology, Laboratory Medicine Program, University Health Network.

Applied Immunohistochemistry & Molecular Morphology : AIMM
|February 22, 2019
PubMed

Insights

External quality assurance for PD-L1 testing presents challenges. Applying "fit-for-purpose" principles to proficiency testing (PT) runs enhances patient safety by improving diagnostic accuracy assessment for immunohistochemistry assays.

Area of Science:

  • Oncology
  • Pathology
  • Clinical Diagnostics

Background:

  • PD-L1 testing via immunohistochemistry (IHC) poses significant challenges for clinical laboratories and external quality assurance (EQA) programs.
  • Proficiency testing (PT) for predictive biomarkers necessitates a "fit-for-purpose" approach at all stages, from design to reporting.

Purpose of the Study:

  • To explore approaches for sample design and result analysis in PD-L1 PT runs to enhance patient safety.
  • To apply "fit-for-purpose" principles to PD-L1 PT runs, ensuring accurate assessment of diagnostic assays.

Main Methods:

  • Canadian Immunohistochemistry Quality Control (CIQC) conducted educational PT runs using unstained slides with tissue cores from 104 primary NSCLC and tonsil tissues.
  • Laboratories tested tissues with their current PD-L1 assays.
  • Diagnostic sensitivity and specificity were calculated against "gold standards" using the "3D" approach (drug-disease-diagnostic assay).

Main Results:

  • Significant variation in the performance (accuracy) of diagnostic assays was observed, dependent on the selection of "fit-for-purpose" gold standards and cut-off points.
  • The study highlighted the impact of chosen standards and cut-offs on assay performance evaluation.

Conclusions:

  • "Fit-for-purpose" in PD-L1 PT requires clearly declared run purposes, designated purpose-specific gold standards, and PT materials designed for accurate diagnostic assessment.
  • Implementing "fit-for-purpose" principles is crucial for reliable PD-L1 testing and improved patient safety.

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