Cytogenic studies over the past 50 years have hinted at the impact that copy number variations (CNVs) can have on phenotypic traits and disease susceptibility. Given the high incidence and clinical impact of CNVs, a precise, rapid and cost-effective method is needed for high-throughput validation of candidate CNV associations and for subsequent routing deployment in diagnostic settings. The predominant method used to validate CNVs in larger population is real-time or quantitative PCR (qPCR), which measures the relative rates of fluorescence increases during the exponential amplification of target and single-copy reference genes. The accuracy and precision of these measurements can be impacted by multiple factors including differences in amplification rates between the target and reference genes, variations in their amplification rates during qPCR, sampling error due to DNA concentration and analysis errors. Weaver et al. rigorously characterized these factors and found that systemic errors can be addressed by increasing the number of replicates to achieve the desired precision. however, the required number of replicates increases rapidly as finer discrimination is desired, with four replicates required to distinguish a twofold difference and up to 18 replicates to distinguish a 1.25-fold difference.
Read Digital PCR – Probing Copy Number Variations Using Bio-Rad’s QX100 Droplet Digital PCR System to learn more on how droplet digital PCR (ddPCR) can be used to determine small fold differences for higher-order CNV states.