Abstract: Background　Colorectal cancer（CRC）is a common malignant tumor of the digestive system，its morbidity and mortality present a year-by-year ascending tendency.Early diagnosis and treatment are the key to CRC prevention and treatment.However，there is short of noninvasive，simple，convenient and effective detecting methods for clinical diagnosis of CRC.Objective　To probe into the diagnostic value of plasma SEPT9 methylation test（mSEPT9）for CRC，to provide evidence for the diagnosis of this disease.Methods　Two hundred and seventy-two（126 cases of CRC，146 cases of non-CRC）cases of patients who visited the gastroenterology，gastrointestinal surgery and oncology departments of First Affiliated Hospital of Kunming Medical University between December 2017 and December 2018 were enrolled.They were divided into control group（82 cases），colorectal adenoma group（64 cases），early CRC group（72 cases）and progressive CRC group（54 cases）according to colonoscopy and pathological examination results.The relationship between positive expression of plasma mSEPT9 and the clinical characteristics of CRC patients was analyzed.The diagnostic performance of plasma mSEPT9 and serum carcinoembryonic antigen（CEA），and the combination of the two for early and progressive CRC was compared，and the accuracy of these three tests were evaluated.Results　The positive rate of plasma mSEPT9 was not related to CRC patients' age，gender，tumor location or tumor diameter（P>0.05）.The positive rate of plasma mSEPT9 was significantly lower in early CRC patients than that of progressive CRC patients（P<0.001）.The positive rate of plasma mSEPT9 was significantly higher in CRC patients with lymph node metastasis than that of those without（P<0.001）.The positive rate of plasma mSEPT9，serum CEA and the combination of the two for CRC showed significant differences across the four groups（P<0.001）.The combination of plasma mSEPT9 and serum CEA for CRC diagnosing was superior to either plasma mSEPT9 or serum CEA in terms of sensitivity，accuracy，negative predictive values，and its Kappa value was 0.514，indicating a moderate level of agreement with the gold standard.Conclusion　In the diagnosing for early and progressive CRC，the plasma mSEPT9 showed higher accuracy than serum CEA，but the accuracy of the combination of these two may be higher（in terms of sensitivity，accuracy，negative predictive values，and level of agreement with the gold standard），which may be used as a new thought or method for the diagnosis of CRC.

Key words: Plasma SEPT9, Methylation, Colorectal neoplasms, Carcinoembryonic antigen, Genetic testing, Diagnosis

摘要： 背景　结直肠癌（CRC）是消化系统常见的恶性肿瘤之一，其发病率和病死率呈逐年上升的趋势，早诊断和早治疗是防治CRC的关键，然而目前临床上仍缺乏确诊CRC的无创、简便、有效的检测方法。目的　探讨血浆SEPT9甲基化（mSEPT9）检测对CRC的诊断价值，提供CRC诊断依据。方法　选取2017年12月—2018年12月于昆明医科大学第一附属医院消化内科、胃肠外科及肿瘤科就诊的患者共272例（CRC 126例，非CRC 146例）为研究对象，按结肠镜检查及术后病理检查结果分为对照组82例、腺瘤组64例、早期癌组72例、进展期癌组54例，分析血浆mSEPT9阳性表达与CRC患者临床特征的关系；探讨血浆mSEPT9、血清癌胚抗原（CEA）及二者联合检测在4组患者中阳性率的差异；评估血浆mSEPT9、血清CEA及二者联合检测诊断CRC的价值。结果　不同年龄、性别、肿瘤部位、肿瘤最大直径CRC患者mSEPT9阳性率比较，差异无统计学意义（P>0.05）；早期癌患者血浆mSEPT9阳性率低于进展期癌患者，有淋巴结转移患者血浆mSEPT9阳性率高于无淋巴结转移患者（P<0.001）。对照组、腺瘤组、早期癌组和进展期癌组患者血浆mSEPT9、血清CEA及二者联合检测的阳性率比较，差异均有统计学意义（P<0.001）。血浆mSEPT9及血清CEA联合检测的灵敏度、准确度、阴性预测值高于单一指标检测，血浆mSEPT9联合血清CEA检测与金标准诊断一致性检验，Kappa值为0.514。结论　在早期和进展期CRC患者中，血浆mSEPT9检测的阳性率均高于血清CEA，二者联合检测对CRC的诊断价值（灵敏度、准确度、阴性预测值、与金标准诊断的一致性）可进一步提高，这为CRC的确诊提供了新思路、新方法。

关键词: 血浆SEPT9, 甲基化, 结直肠肿瘤, 癌胚抗原, 基因检测, 诊断