The stool

Background: Methylated Methods: The gold standard diagnostic technique that was used was colonoscopy combined with a pathological analysis of biopsied tissue. Stool DNA was extracted from 1,002 stool samples (445 from CRCs, 115 from adenomas, and 442 from controls) and then bisulfite-converted, followed by real-time quantitative methylation-specific polymerase chain reaction. Blood mSEPT9 levels were quantified by the Epi proColon 2.0 assay, and serum CEA, CA19-9 and CA724 levels were measured by electrochemiluminescence. The main indexes used during the evaluation were sensitivity, specificity and the area under the receiver operating characteristic curve (AUC). Results: Stool mSDC2 detected 69.7% of CRCs, which was significantly higher than 53.8% by plasma mSEPT9, 37.2% by CEA, 13.1% by CA19-9 and 17.5% by CA724; for adenoma, the detection rates were 31.3%, 11.1%, 2.3% and 11.9%, respectively. The AUC of mSDC2 in detecting CRC was 0.83, compared to 0.72, 0.75, 0.63 and 0.54 for mSEPT9, CEA, CA19-9 and CA724, respectively. mSDC2 identified patients with stage I-III CRC with a sensitivity of 71.6%, which was significantly higher than that of mSEPT9, CEA, CA19-9 and CA724 (54.2%, 35.5%, 11.9%, and 15.0%, respectively); for stage IV CRC, the sensitivities of mSDC2, mSEPT9, CEA, CA19-9 and CA724 were 75.9%, 82.6%, 79.3%, 36.0% and 56.5%, respectively. SDC2 and CEA had a significantly higher sensitivity for distal CRC than for proximal CRC. Conclusions: The stool SDC2 methylation test had a better performance in detecting nonmetastatic CRC and adenoma than evaluations of mSEPT9, CEA, CA19-9 and CA724 in blood. Our findings could be used to modify approaches for CRC prevention and early detection.