Abstract: Objective To construct a stool- based human protein diagnostic system using the Luminex liquid chip system for early diagnosis of colorectal tumors. Methods From January, 2021 to January, 2023, 70 patients with colorectal cancer (CRC), 42 patients with colorectal adenoma (CRA), and 38 healthy individuals were recruited from our hospital for detecting fecal protein levels of matrix metalloproteinase-9 (MMP-9), retinol- binding protein 4 (RBP4), chitinase-3-like protein 1 (CHI3L1), and complement component 3a (C3a) using Luminex liquid chip technology and serum levels of carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) using chemiluminescence assay. Receiver-operating characteristic (ROC) curve analysis was used for assessing the diagnostic efficacy of the combination of MMP- 9, RBP4, CHI3L1 and C3a and the combination of CEA and CA19-9 for colorectal tumors. Results The fecal contents of MMP-9, RBP4, CHI3L1, and C3a were significantly higher in CRC patients than in healthy individuals (P<0.05). Fecal MMP-9 and CHI3L1 levels were significantly higher in CRC than in CRA patients (P<0.05), but RBP4 and C3a levels did not differ significantly (P>0.05). CRC patients had significantly higher serum CEA and CA19- 9 levels than healthy individuals and CRA patients (P<0.05), but the differences were not significant between the latter two groups (P>0.05). ROC analysis showed that the sensitivity and specificity of the combination of MMP-9, RBP4, CHI3L1, and C3a was 91.4% and 100.0%, for diagnosing CRC, 81.0% and 89.5% for diagnosing CRA, and 83.9% and 97.4% for a combined diagnosis of CRC and CRA, respectively. Z-test analysis indicated that fecal MMP-9, RBP4, CHI3L1, and C3a contents had a greater diagnostic efficacy than serum tumor markers CEA and CA19-9 for a combined diagnosis of colorectal tumors (P<0.05). Conclusion The Luminex liquid chip detection system for detecting decal RBP4, MMP-9, CHI3L1, and C3a provides an effective means for early diagnosis of colorectal tumors with a greater diagnostic efficacy than serum CEA and CA19-9 levels.

Key words: colorectal cancer; early diagnosis; fecal protein; Luminex liquid chip technology