OverC® is Burning Rock Dx's multi-cancer early detection test built on the ELSA-seq technology platform. It screens more than 70,000 methylation regions on circulating cell-free DNA (cfDNA) by next-generation sequencing. This article summarizes the technology and analytical framework.
The ELSA-seq Platform
- Single-strand library preparation: stable sequencing libraries are produced from extremely low amounts of cfDNA (minimum 0.5 ng).
- Single-base resolution: methylation status is profiled at single-base resolution across the relevant regions.
- Publication: the technology was published in Nature Biomedical Engineering (Liang N et al., 2021).
The Logic of Methylation-Based Detection
Cancer cells leave methylation marks that differ from healthy cells and carry tissue-specific information. These marks appear early, produce strong signals and allow tracing the origin of the cancer tissue. OverC® comprehensively screens the regions associated with the six cancer types (lung, esophageal, colorectal, liver, pancreatic, ovarian).
The BRMERMAID® Algorithm and Scoring
- The machine-learning-based BRMERMAID® algorithm recognizes single-molecule mutation patterns and applies knowledge-based multi-level noise reduction.
- If the computed cancer signal comprehensive score is ≥ 0.5 the result is "Cancer-Associated Methylation Signals: Detected"; below it, "Not Detected".
- When a signal is detected, a tissue-of-origin prediction is produced.
Analytical Quality Framework
- The analysis is monitored through 16 quality-control steps; sample-level QC parameters include DNA concentration (≥0.33 ng/µL), methylation signal density (≥350) and signal purity.
- Laboratory accreditations: CAP (College of American Pathologists), CLIA (US clinical laboratory accreditation) and the Guangdong Clinical Laboratory Center "High-Throughput Sequencing Laboratory" certificate.
- Imported test tubes are used; samples are shipped to the laboratory at room temperature.
References
- Liang N et al. Nat Biomed Eng. 2021 Jun;5(6):586-599 (ELSA-seq technology).
- Burning Rock Dx OverC® product documentation (brbiotech.com).
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