NAT testing for HBV,HCV,HIV on donors' samples negative by ELISA tests

Objective To perform NAT testing on samples negative for HBsAg, anti-HCV and anti-HIV by ELISA, and to learn how many infected blood samples could be missed by ELISA tests.Methods Pooling the donor samples by STAR2000 sampling processor and extracting nucleic acid automatically, HBV DNA, HCV RNA and HIV-1 RNA were amplified and detected by Roche COBAS AmpliScreen TM HBV、HCV V2.0 和HIV-1 V1.5 systems. Samples of 8 donors with negative HBsAg but positive HBV DNA were tested by COBAS HBV MONITOR TM for quantitative determinations. HBsAg confirmation tests were done every 2 weeks by ABBOTT Murex HBsAg V3.Results A total of 16320 ELISA negative donor samples were tested and 8 samples were HBV DNA positive. The missing rate was 0.49‰. No HCV RNA and HIV-1 RNA were detected. Those 8 donor samples, negative for HBsAg but positive for HBV DNA,were all positive for HBcAb by ABBOTT,and 3 of them were positive for HbeAb Low serum HBV DNA loads, in the range of 102~103 copies/ml, were found in the 8 donor samples. HBsAg confirmations were performed and one donor became HBsAg positive after 18 weeks.Conclusion The results show that there is 0.49‰ missing rate of HBV with HBsAg screening by ELISA. HBcAb screening or NAT may be warranted in blood donor screening to limit HBV transmission through blood transfusion.The reason for missing HBV positive samples by ELISA could be occult HBV infection.