What type of MRD assay is Precise MRD?

• A. RNA-based expression assay
• B. Protein-based assay
• C. PCR-only assay
• D. Tumor-informed, whole genome sequencing-based assay

Answer: (D)

Detecting minimal residual disease relies on tracking cancer-specific signals in the blood after treatment. Precise MRD is designed as a tumor-informed, whole-genome sequencing–based test: it starts by sequencing the patient’s tumor to identify its unique set of mutations, then monitors those exact mutations in the patient's plasma cell-free DNA with ultra-deep sequencing. Because you’re following mutations that come specifically from that individual’s tumor, the test achieves very high sensitivity and specificity for residual cancer, even when tumor burden is extremely low. This approach stands apart from RNA-based expression assays, which measure gene activity that can be influenced by non-tumor factors; protein-based assays that rely on surface markers; or PCR-only assays that target a limited, predefined mutation set and may miss other cancer clones. A tumor-informed, whole-genome sequencing–based strategy also captures a broad mutational landscape and tumor heterogeneity, increasing the chance of detecting any remaining malignant cells. It does require tumor tissue for the initial sequencing and can be more resource-intensive, but offers comprehensive and sensitive MRD detection, which is why this type is used.