Abstract: Objective To explore the rationality of the grey zone determination in anti-HIV detections by ELISA in screening of blood donation. Method sA retrospective analysis was performed with anti-HIV positive and grey zone (0.5≤s/co<1) specimens that were subsequently subjected to Tongling Center for Disease Control for confirmation from January 2014 to December 2017. The ROC curve was used to compare the sensitivity and specificity of the reagents under different s/co conditions. Twenty negative specimens of anti-HIV(s/co<0.5 ) were randomly selected for WB tests. Results A total of 39991 specimens were tested by the reagents from Wantai company,and 26 positive specimens and 22 grey zone specimens were found. Fifteen positive and 7 grey zone specimens were detected out by the reagents provided by Lizhu company. Among them,however,only 5 specimens were confirmed to be positive by Tongling CDC. Conclusion The over-sensitive values of s /co recommended by the reagent manufacturers for blood screening is able to meet our requirements and the setting of grey zone may cause unnecessary waste of donated blood.

Key words: Grey, zone, ROC, curve, Anti-HIV, ELISA