Abstract: Objective To analyze the serological characteristics and HBV DNA levels of HBsAg-negative blood donors with occult HBV infection and their correlation. Methods The blood donors were screened for HBsAg by two different ELISA reagants and the qualified samples were tested for HBV DNA by nucleic acid amplification （NAT）. The positive blood donors were further tested by HBV marker detection and Quantitative Real-time PCR for HBV DNA. Results A total of 29890 samples were detected HBsAg negative by twice ELISA test. Of the 29890 HBsAg-negative samples,31 were detected positive for HBV DNA by NAT. Among the 31 donations screened non-reactive in both rounds of HBsAg testing by ELISA,3 cases were reactive for HBsAg by the means of chemiluminescence. Among the 28 HBsAg - HBV DNA + donations,2 cases （7.1%）were identified as window period infection and 26 cases （92.9%）were identified as occult HBV infection （OBI）. NAT lowered the residual risk of HBV by 9.37/10⁴. On the basis of the serological profile,OBI can be mainly distinguished into two seropositive patterns （HBsAb and HBcAb positive or isolated HBcAb positive）. Of the 28 OBI donations,the HBV DNA levels with HBsAb negative was higher than that with HBsAb positive （P<0.05）. Conclusion HBV remains a risk of transfusion-transmitted infection through ELISA detection in HBsAg-negative blood donors,and OBI is frequent. The application of NAT in blood screening is very important for assuring the safety of blood. The OBI blood donors with HBsAg-negative have certain serological patterns,in which HBsAb-negative donors may have a higher residual risk of transfusion-transmitted HBV infection.

Key words: HBsAg, Occult HBV infection, Nucletic acid testing, Residual risk, Blood donors