Abstract:

Objective: To compare the results of three brands of ELISA (enzyme-linked immunosorbent assay） kits for detection of serum anti-Saccharomyces cerevisiae antibody ASCA)and to evaluate the performance of each kit for clinical reference. Methods: One hundred and forty patients with inflammatory bowel disease (IBD) were enrolled, including 53 patients with ulcerative colitis (UC), 87 patients with Crohn'sdisease (CD); and 40 other patients were served as disease control group (DC). Three ELISA kits (kid A is a domestic brand, B and C are imported brands) were used to detect ASCA-IgA and ASCA-IgG, and the results were analyzed and compared. Results: The detection rates of ASCA-IgA and/or ASCA-IgG in CD group were higher than those in UC group and DC group (P<0.05), but there was no significant difference between UC group and DC group (P>0.05). In UC group and DC group, the positive rates of three kits had no significant difference (P>0.05); in CD group, the positive rates of kit A and B had no significant difference (P>0.05), but the result of kit C was lower than that of kit A and B (P<0.05). The results of consistency analysis showed that kits A and B had moderate consistency in detecting ASCA-IgA (Kappa: 0.423), kits A and C, kits B and C showed poor consistency (Kappa: 0.111 and 0.074, respectively); kits A and B, kits B and C and kits A and C showed moderate consistency in detecting ASCA-IgG (Kappa: 0.414, 0.447 and 0.584, respectively). The analytical performance of detecting ASCA-IgA, ASCA-IgG by three ELISA kits separately and jointly for the diagnosis of IBD showed that the sensitivity was kit A (37.90%, 27.86%, 43.57%), kit B (20.71%, 45.00%, 51.43%), kit C (9.29%, 22.14%, 25.71%); specificity was kit A (87.5%, 85.00%, 77.50%), kit B (92.50%, 90.00%, 87.50%) and kit C (97.5%, 90.0%, 87.50%). The Youden index was kit A (0.25, 0.12, 0.21), kit B (0.13, 0.35, 0.38), kit C (0.07, 0.12, 0.13). The AUC area obtained by receiver operating characteristic (ROC) curve were kit A(0.72, 0.54, 0.59), kit B (0.54, 0.72, 0.69), kit C (0.64, 0.52, 0.57). Conclusions: All the three kits had high positive rate in CD group, It showed that ELISA detection of ASCA has certain application value for the diagnosis and differential diagnosis of CD. The consistency of test results of different kits was not satisfactory, the consistency of the results of ASCA-IgG was better than that of ASCA-IgA. All three kits have low sensitivity and are not suitable for IBD screening of the population. Detecting ASCA-IgG and ASCA-IgA antibodies simultaneously could improve the detection sensitivity. Test performance showes kit B > A >C. The imported kit is not necessarily superior to the domestic kit, and the brand of kit should be selected according to the actual situation.

Key words: Crohn’s disease, Ulcerative colitis, Anti-saccharomyces cerevisiae antibody, Enzyme-linked immunosorbent assay