External quality assessment for detection of methylated Syndecan 2 (SDC2) in China

Detection of Syndecan 2 (SDC2) methylation in stool DNA is a novel method for the auxiliary diagnosis of early colorectal cancer (CRC). Currently, this method has been widely applied; however, its accuracy and reliability have not been determined. The objective of this pioneering study was to evaluate the performance of clinical laboratories in China for their ability to detect SDC2 methylation from stool DNA.We generated a sample panel consisting of clinical and cell samples. The clinical samples were stool specimens from patients with or without CRC, including four positives (prepared by serial dilution from one stool specimen), one negative and one interferential sample. Two cell samples, with positive or negative methylated SDC2, were used as controls. The panel was distributed to 32 clinical laboratories for analysis of SDC2 methylation, and the results were compared and scored.The sample panel was compatible with commercially available assays and it showed appropriate stability to be an external quality assessment material. There were four false results; one hospital laboratory and one commercial diagnostic laboratory had a false-positive and a false-negative result, respectively, and one commercial diagnostic laboratory had both a false-positive and false-negative result. Among the 32 participating laboratories, 29 (90.62%) obtained an acceptable or better performance score, while 3 (9.38%) laboratories required improvement.Our results demonstrate that the detection of SDC2 methylation from stool DNA was satisfactory in China. Additionally, the importance of external quality assessment was highlighted for monitoring the performance of clinical laboratories.