Digital PCR in Translational Medicine

Digital PCR (dPCR) has become a practical tool in translational medicine as demands for precision and sensitivity continue to rise. Its ability to deliver reliable, absolute quantification has led to its growing use in gene expression analysis, rare variant detection, clinical diagnostics, and more.

Strengths of dPCR

Unlike traditional PCR, which relies on endpoint measurements, or qPCR, which estimates abundance through fluorescence and standard curves, dPCR follows a different strategy. “dPCR works on the principle of partitioning the reaction into thousands of individual reactions prior to amplification—each containing a single (or no) template molecule,” stated Eric Cooper, Marketing Manager, Roche Sequencing & Life Science. After amplification is completed, each partition is scored as positive or negative based on fluorescence. By counting positive and negative partitions, dPCR enables the direct and absolute quantification of the starting material without the need for reference standards.

Cooper explained that this partitioning strategy gives dPCR several practical advantages, including tolerance to PCR inhibitors, increased sensitivity for low-abundance targets, and high precision across a wide dynamic range. Sensitivity increases further as the number of partitions rises, supporting applications that require accurate measurement of rare sequences or limited input material.

Real-world dPCR applications

These performance characteristics have made dPCR a practical choice in settings where quantitative confidence is essential. “Given its high specificity, dPCR has been extensively used for the detection of mutations and single-nucleotide polymorphisms (SNPs), particularly when the mutation frequency is known to be below 1%,” explained Marwan A. Alsarraj, Global Segment Manager, Life Science Group, Bio-Rad Laboratories. He added that dPCR excels at resolving rare mutations against wild-type backgrounds, characterizing haplotypes, and quantifying low-abundance targets in liquid biopsy samples, including circulating tumor cells and cell-free DNA.

Cooper also noted that dPCR performs well in high-sensitivity settings such as minimal residual disease (MRD) monitoring, transplant rejection, and detection of rare allelic variants that are difficult to detect with qPCR or next-generation sequencing. The method is also commonly used in gene editing studies, where desired and off-target edits often occur at very low frequencies. In addition, dPCR has been frequently applied to wastewater testing for infectious diseases, as reaction partitioning reduces the impact of PCR inhibitors and supports more reliable detection in complex samples.

Expanding roles in translational medicine

Among translational researchers, cell and gene therapy and oncology represent the most active areas of interest, explained Alsarraj. He shared that in oncology research, MRD monitoring and recurrence surveillance are prominent use cases, with groups applying tumor-informed droplet digital PCR (ddPCR) to track residual disease in patients with solid tumors after treatment. Similar personalized ddPCR approaches have been used to monitor circulating tumor DNA following colorectal cancer surgery and to identify patients at higher risk of recurrence.¹ Alsarraj noted that dPCR is also being applied to gene therapy development and biopharmaceutical quality control. For instance, in AAV vector production, dPCR has been used to assess empty and full capsid populations, supporting measurement of capsid titer, genome titer, and vector composition during development and manufacturing workflows.

Advances in platforms

Many translational dPCR applications have been enabled by advances in platform design that support diverse sample types and analytical needs while lowering barriers to adoption. “Our ddPCR platforms are designed to give researchers the highest level of precision, sensitivity, and workflow simplicity across the full spectrum of digital PCR applications,” stated Alsarraj. He emphasized that with systems spanning the QX200, QX600, QX Continuum, and QX700 series, users can select platforms suited to translational research, oncology, infectious disease, environmental testing, and biopharma workflows. Recent platform updates include qPCR-like workflows with four-color multiplexing on QX Continuum and high-throughput, seven-color multiplexing with continuous loading on QX700 for large-scale studies.

While individual platforms vary in technical design, many share common goals related to flexibility, multiplexing, and application-driven performance. Cooper described the Digital LightCycler system as “a high-quality digital PCR system that’s sensitive, precise, and flexible,” highlighting its use of multiple optical channels to support multiplexed DNA and RNA assays. He also stated that the platform offers three solid nanowell plate formats with different partition densities that give labs the ability to optimize performance for specific applications. These options support use cases ranging from the detection of rare mutations in oncology to gene expression studies and the monitoring of transplant rejection.

Integrating dPCR into the lab

Despite its growing use, dPCR is still accompanied by misconceptions that influence its adoption. One common assumption is that qPCR is inherently more cost-effective and efficient due to smaller reaction volumes and established multiplexing strategies. Alsarraj noted that while this was once true, the gap has narrowed as dPCR platforms have matured. Because amplification efficiency is not a limiting factor, he explained that dPCR can simplify multiplexing, reduce the need for repeat testing, and become more cost-effective over time, particularly when sample material is limited or the targets are rare.

Another misconception is that dPCR is restricted to highly specialized use cases. However, many labs now routinely use dPCR in translational studies because of its absolute quantification, precision, and reproducibility. Concerns about workflow complexity have also persisted, particularly in labs accustomed to qPCR. Both Alsarraj and Cooper pointed to newer platforms that use familiar workflows and software interfaces, lowering the barrier for routine use without requiring extensive retraining.

There is also a lingering perception that dPCR offers limited multiplexing or dynamic range. Alsarraj emphasized that advances in multi-color detection and assay design have expanded both, enabling reliable quantification of multiple targets across wide concentration ranges. Cooper added that dPCR is often most effective when used with existing methods rather than as a replacement. In workflows that include sequencing, dPCR is frequently used for library quantification, validation of rare variants, and longitudinal monitoring, reinforcing its role as a practical, complementary tool rather than a niche technique.

Where dPCR is headed

For laboratories using dPCR in translational work, practical considerations now play a larger role in adoption. “The future of digital PCR will primarily be driven by advancements that will enhance its throughput, automation, multiplexing capabilities, and integration into clinical settings,” stated Cooper. Expanded clinical applications driving broader adoption in diagnostics are projected to have the greatest influence on translational medicine in the coming years. Cooper also believes that using dPCR for applications such as cancer liquid biopsy, genetic and prenatal testing, and infectious disease diagnostics will play a key role in its continued clinical expansion.

Alsarraj anticipates that tumor-informed MRD monitoring using ctDNA will become routine, supported by dPCR’s absolute quantification and tolerance to inhibitors. “Multiplexing advances, such as six-color and beyond, will enable comprehensive variant panels in a single well, reducing cost and sample burden,” he emphasized. Finally, Alsarraj noted that standardization efforts through ISO and CLSI, along with IVD-ready platforms, are expected to accelerate clinical adoption, while harmonized cfDNA preanalytical workflows will improve reproducibility between laboratories.

Reference

1. Henriksen TV, Demuth C, Frydendahl A, et al. Unraveling the potential clinical utility of circulating tumor DNA detection in colorectal cancer—evaluation in a nationwide Danish cohort. Ann Oncol. 2024;35(2):229-239. doi:10.1016/j.annonc.2023.11.009