Analytical validation of the DropXpert S6 system for diagnosis of chronic myelocytic leukemia

Digital PCR is a powerful method for absolute nucleic acid quantification and is widely used in the absolute quantification of viral copy numbers, tumor marker detection, and prenatal diagnosis. However, for most of the existing droplet-based dPCR systems, the droplet generation, PCR reaction, and droplet detection are performed separately using different instruments. Making digital PCR both easy to use and practical by integrating the qPCR workflow into a superior all-in-one walkaway solution is one of the core ideas. A new innovative and integrated digital droplet PCR platform was developed that utilizes cutting-edge microfluidics to integrate dPCR workflows onto a single consumable chip. This makes previously complex workflows fast and simple; the whole process of droplet generation, PCR amplification, and droplet detection is completed on one chip, which meets the clinical requirement of "sample in, result out". It provides high multiplexing capabilities and strong sensitivity while all measurements were within the 95% confidence interval. This study is the first validation of the DropXpert S6 system and focuses primarily on verifying its reliability, repeatability, and consistency. In addition, the accuracy, detection limit, linearity, and precision of the system were evaluated after sample collection. Among them, the accuracy assessment by calculating the absolute bias of each target gene yielded a range from -0.1 to 0.08, all within ±0.5 logarithmic orders of magnitude; the LOB for the assay was set at 0, and the LoD value calculated using probit curves is MR4.7 (0.002%); the linearity evaluation showed that the R² value of the BCR-ABL was 0.9996, and the R² value of the ABL metrics calculated using the ERM standard was 0.9999; and the precision evaluation showed that all samples had a CV of less than 4% for intra-day, inter-day, and inter-instrument variation. The CV of inter-batch variation was less than 7%. The total CV was less than 5%. The results of the study demonstrate that dd-PCR can be applied to molecular detection and the clinical evaluation of CML patients and provide more precise personal treatment guidance, and its reproducibility predicts the future development of a wide range of clinical applications.