STUDIES ON THE DETECTION KIT FOR THE COLORECTAL CARCINOMA ASSOCIATED LARGE EXTERNAL ANTIGEN

Objective: To investigate the detecting method and diagnostic value of the tumor marker colorectal carcinoma associated large external antigen (LEA) for colorectal carcinoma. Methods: Monoclonal antibody ND-1, which can recognize LEA, was labeled with biotin aminocaproylhydrazide (BACH) and horseradish peroxidase (HRP) respectively. One step sandwich ELISA Kit for detecting LEA in serum was developed by the biotinylated antibody and enzyme conjugation. The validity and reliability of the kit were evaluated by sera selected from clinic. Results: the OD405 of healthy group was 0.056±0.038, and that of patients was 0.553±0.441. The difference between the two groups was significant (P<0.01). The cutoff value, which was 0.248, was determined by analysis of ROC. The diagnosis sensitivity, specificity and validity of the kit were 89.29%, 87.5%, 88.54% respectively. The ROC value was 0.95. The intra-CV was less than 5%, and the internal-CV was less than 10%. There was no significant difference between the results obtained by the kit and those obtained by pathological diagnosis (P<0.01). The expression of LEA was associated with the differentiated degree of colorectal carcinoma and had no relation to the Dukes’ phase of the disease. Conclusion: LEA is practically useful tumor marker for the diagnosis of colorectal carcinoma. The kit developed can be used for the qualitative diagnosis for the disease.

THE STUDY OF COLORECTAL CARCINOMA ASSOCIATED ANTIGEN LEA IN CLINICAL PATHOLOGICAL DIAGNOSIS

Objective: To study the expression and the clinical significance of LEA in colorectal carcinoma. Methods: Immunohistochemistry S-P method to detect the expression of LEA and CEA in 140 colorectal cancer specimens and 100 non-cancerous colorectal specimens. Results: The expression of LEA is relative to tumor differentiation degree and exhibits higher selectivity in well-differentiated adeno-carcinoma (P<0.01). CEA has similar selectivity in well, moderately and poorly differentiated adenocarcinoma (P>0.05). Compared with CEA, the expression of LEA has lower positive rate in non-cancerous tissue (P<0.05). The positive rate of LEA in adenoma is much higher than surrounding non-cancerous mucosa and normal mucosa. In normal mucosa the positive rate of LEA is obviously lower than that of CEA (P<0.05). The expression of LEA and CEA has similar rule except in normal mucosa. In histological diagnosis of colorectal cancer the sensitivity of LEA is 82.9% and the specificity is 48%, while the sensitivity of CEA is 88.6% and the specificity is 35%. Conclusion: The expression of LEA is related to the differentiation degree of colorectal cancer tissue. LEA can be used as an auxiliary index for early diagnosis and a reference for the judgment of the malignancy degree of colorectal carcinoma, thus may be a new tumor marker with applicable clinic value.