Applying Standard Clinical Chemistry Assay Validation to Droplet Digital PCR Quantitative Liquid Biopsy Testing

Area of Science:

• Molecular Diagnostics
• Oncology
• Biotechnology

Background:

• Droplet digital PCR (ddPCR) shows promise for quantitative cell-free DNA analysis in oncology.
• Standardized assay validation is crucial for realizing the full potential of ddPCR technology.
• Existing clinical chemistry assay validation protocols can be adapted for ddPCR.

Purpose of the Study:

• To validate quantitative ddPCR assays for oncology applications using established clinical chemistry guidelines.
• To assess the performance criteria of ddPCR assays for KRAS, EGFR, and BRAF mutations.
• To demonstrate the applicability of standard laboratory-developed test regulations to ddPCR.

Main Methods:

• Validated KRAS, EGFR, and BRAF quantitative ddPCR assays following Clinical Laboratory Improvement Act regulations and CLSI guidelines.
• Evaluated key performance metrics including LOB, LOD, LOQ, imprecision, analytical range, linearity, accuracy, and stability.
• Compared ddPCR results with orthogonal platforms like next-generation sequencing.

Main Results:

• Established ddPCR assay parameters: LOB (4 copies), LOD (12-22 copies), LOQ (35-64 copies), and dynamic range up to 30,000 copies.
• Demonstrated excellent linearity down to LOQ and accurate spike recovery.
• Achieved qualitative agreement and quantitative concordance with orthogonal methods (R² 0.83-0.99).
• Determined reference range for wild-type copies in plasma (462-6169/mL).

Conclusions:

• Standard clinical chemistry assay validation protocols are suitable for quantitative ddPCR assays.
• This standardization facilitates assay performance comparison and the establishment of minimal significant change thresholds for monitoring.
• Validated ddPCR assays provide reliable quantitative data for oncology applications.