Abstract: Objective: To investigate the resolution of sampling probe towing positive in automatic enzyme immunoassay instrument.Methods: Anti-human immunodeficiency virus (HIV),anti-treponema pallidum (TP),anti-hepatitis C virus (HCV) or hepatitis B surface antigen (HBsAg) strong positive specimens were collected from routine screening test.The towing positive simulation test was performed in RMP 200 automatic enzyme immunoassay under use of demineralized water or 0.1% Tween-20 weak alkaline solution for sampling probe irrigation solutions conditions.By comparison of the two groups results,it was observed that 0.1% Tween-20 weak alkaline solution in role of avoid sampling probe towing positive and it effect on ELISA.Results: It was found that every of anti-HIV,anti-TP,anti-HCV,and HBsAg sepecimen had experienced towing positive under use of demineralized water for sampling probe irrigation solutions.Among them,anti-HIV towing positive was most obvious and had 6 towing positive holes;while HBsAg appeared only a towing weak positive hole.In contrast to demineralized water,all towing positive phenomena of anti-HIV,anti-TP,anti-HCV and HBsAg strong positive specimens were avoided under use of 0.1% Tween-20 weak alkaline solution for sampling probe irrigation solutions.Moreover,the results of quality control serum,positive and negative control under two different irrigation solutions had no significant difference for the same test item (P>0.05).Conclusions: The use of 0.1% Tween-20 weak alkaline solution for sampling probe irrigation solutions could avoid appearance of sampling probe towing positive in automatic enzyme immunoassay instrument and it had no significant effect on ELISA.