Allele-Specific Digital PCR Enhances Precision and Sensitivity in the Detection and Quantification of Copy Number...

Area of Science:

• Genomics
• Molecular Diagnostics
• Cancer Research

Background:

• Accurate measurement of copy number (CN) alterations is crucial for cancer diagnostics but challenging in heterogeneous samples like biopsies.
• Digital PCR is a key technology, traditionally using reference genes or allelic imbalance of single-nucleotide polymorphisms (SNPs) for CN quantification.
• The SNP-based method leverages the allelic imbalance of heterozygous germline SNPs within the target locus for CN measurement.

Purpose of the Study:

• To compare the precision and sensitivity of classic digital PCR methods versus a novel SNP-based approach for measuring CN alterations.
• To evaluate these methods in silico and in vitro using control and biological samples, including FFPE specimens.

Main Methods:

• In silico and in vitro evaluation of classic and SNP-based digital PCR approaches.
• Analysis of control samples with known CN values and biological specimens (uveal melanomas, FFPE samples).
• Duplex and multiplex experimental setups focusing on heterozygosity for SNPs on chromosomes 3p and 8q.

Main Results:

• Both methods yielded accurate CN values under ideal conditions (stable reference for classic, single variant imbalance for SNP-based).
• The SNP-based approach demonstrated superior precision and sensitivity for CN values below 4.6 compared to the classic method.
• Detection rates for a CN of 2.1 were approximately 75% with the SNP-based approach versus 40% with the classic approach; SNP-based also outperformed for FFPE samples.

Conclusions:

• The SNP-based approach significantly enhances the detection limits for CN alterations in heterogeneous DNA using digital PCR.
• This improved sensitivity and precision make the SNP-based method particularly valuable for analyzing challenging sample types like FFPE tissues.