Interlaboratory consistency of SDC2 promoter methylation detection in colorectal cancer using the post-optimized materials

Fecal DNA-based Syndecan 2 (<i>SDC2</i>) methylation detection is a promising non-invasive strategy for early colorectal cancer (CRC) screening. In China, commercial assays for <i>SDC2</i> methylation detection vary in sensitivity and specificity, yet there is no standardized external quality assessment (EQA) to ensure accuracy. This study utilized CRISPR-Cas9 and homology-directed repair (HDR) technologies to edit the <i>SDC2</i> promoter in 293T cells, creating hypermethylated and heterogeneous cell lines. These cell lines were used to develop an EQA panel for <i>SDC2</i> methylation. We established a 10-sample panel, encompassing a range of methylation levels, and conducted an EQA across 140 laboratories. Among 1,400 results, 0.57% were incorrect. The optimized EQA materials effectively monitor the accuracy of <i>SDC2</i> methylation detection in CRC, supporting reliable and consistent clinical testing and contributing to early CRC screening and diagnosis in China.