Understanding Biomarker Method Validation: Accuracy & Precision – Beyond Traditional Approaches

Introduction

The January 2025 FDA guidance maintains consistency with previous documents in suggesting biomarker validation should start with approaches used for drug assays. However, our extensive experience in biomarker implementation reveals why accuracy and precision require fundamentally different scientific approaches.

Understanding Traditional Drug Assay Validation

In drug concentration assays, accuracy and precision benefit from a straightforward reality: we can measure recovery of a spiked reference standard against target nominal levels and demonstrate precision through repeated measures of spiked control samples.

The Scientific Challenge of Biomarker Assays

Biomarker measurement presents a fundamentally different challenge. Unlike traditional methods using spiked controls, we must demonstrate accuracy and precision by measuring endogenous molecules with varying native analyte levels. While the approaches differ for accuracy assessment, the fundamental method for precision remains consistent: repeated measurements of the same samples to evaluate measurement variability. The key distinction is not in the method of precision determination, but in the sample type—using actual biological samples with inherent analyte variability rather than controls spiked with reference material.

Scientific Approaches to Biomarker Validation:

Through successful implementation experience, we’ve developed scientifically sound approaches:

Accuracy Assessment

• Determining relative accuracy by assigning ‘nominal’ concentrations from repeated measures of endogenous analyte repeated measures of authentic samples that have low, mid and high levels of endogenous analyte

• Reporting accuracy as bias from these assigned nominal concentrations

• Working with actual biological samples rather than spike-recovery experiments

• Understanding that relative accuracy must be demonstrated for the endogenous analyte itself

Precision Evaluation

• Conducting repeated measurements specifically using samples containing the endogenous analyte

• Demonstrating measurement reliability for a specific matrix type

• Establishing reproducibility using actual biological samples rather than spiked controls

Why This Matters

This scientifically driven approach ensures we’re actually demonstrating method performance for measuring the endogenous biomarker in its natural biological context – the true measure of method reliability.