Objective To establish and confirm the hepatitis B surface antigen(HBsAg) enzyme linked immunosorbent assay(ELISA) high specificity S/CO limit as blood donor deferral criterion.Methods A total of 783 HBsAg ELISA reactive and 588 non-reactive samples were collected, and confirmed by HBsAg electrochemiluminescence detection and neutralization test.Receiver operating characteristic curve (ROC curve) was used to evaluate the S/CO limit under 95% and 99% specificity.Another 124 HBsAg ELSIA reactive samples were tested for five kinds of hepatitis B virus(HBV) markers by using electrochemiluminescence detection to verify the blood donor deferral limit.The blood donor deferral limits of 3 laboratories, using the same reagents, were compared.Results The 95% specificity S/CO limit of two reagents were 0.24 and 0.65, the 99% specificity S/CO limit of two reagents were 3.89 and 3.62.The 99% specificity S/CO limit was set as the blood donor deferral criterion.Verify test indicated that the samples, with S/CO higher than the blood donor reentry limit of reagent 1 and 2, were all from HBV infected donor.The 99% specificity S/CO limits of reagent 1 in the other three laboratories were 3.77, 3.60 and 13.42 respectively.And the 99% specificity S/CO limits of reagent 2 in the other three laboratories were 27.73, 31.75 and 1.17.Conclusion The blood donor deferral limit of HBsAg ELISA could identify the true positive blood donor, and reduce the number of blood donor, entering the reentry process.It might not suit to adopt a unified donor deferral limit in different laboratories, even using the same reagents.

Objective:To evaluate the impact of sample pooling strategy on 2019-nCoV RNA detection results.Methods:Ten negative swabs were stored in 6 ml virus transport medium, mixed thoroughly and diluted 1∶2 and 1∶10. Inactivated 2019-nCoV culture medium was added to simulate pooling samples: 10 pooling samples, 5 pooling samples and 1 swab sample. Extraction and amplification were made using three nucleic acid extraction reagents a, b, and c with different extraction methods and systems, as well as five 2019-nCoV detection reagents A-E with various template loading volumes and sensitivities respectively.Results:For the same sample, the Ct values of extracted templates a were 2.10±0.47 and 3.46±0.62 earlier than extracted templates b and c. For samples with identical amplifying, the Ct valves of N and ORF1ab gene of A reagent were 1.16±0.48 and 2.36±0.54 earlier than that of reagent B. Adding nucleic acid of 10 negative swabs to the amplification system lagged the Ct values of reagent A by about 1.36±0.32 Ct, while Ct values of reagent B were not affected. Extracted by regent a, a lag of 1.66±0.39 Ct on average was observed in C, D, and E reagents in detecting pooling samples of ten swabs as compared with one swab sample. When extracting 400 copies/ml pooling samples of ten swabs by reagent a, N gene could be detected by reagents C and E, but not by reagent D.Conclusion:Large amount of extraneous DNA is introduced by sample pooling, which could interfere the effiency of extraction and amplification. Strategies of using extraction reagents with large loading volume and high effiency, together with amplification reagents with large template volume and low limit of detection are helpful for ensuring detection sensitivity of pooling samples, and greatly reducing the risk of false negative results.