Effect of long-term frozen plasma on the detection of HBsAg by ELISA / 中国输血杂志

【Objective】 To evaluate the HBsAg detection results of HBsAg+ samples after 8 years refrigeration by ELISA and evaluate the effectiveness of the current storage policy of retained samples. 【Methods】 A total of 100 HBsAg+ plasma samples by ELISA from May 2014 to March 2015 and refrigerated at -20℃ were collected and retested for HBsAg using the same method after thawing in 2023. 【Results】 The HBsAg retest results of 100 plasma samples were all positive, with the concordance rate of 100%, though there was a significant decrease in the S/CO value after refrigeration(27.52 vs 19.03, P<0.05). 【Conclusion】 Long-term refrigeration can lead to a decrease in the S/CO value of HBsAg ELISA detection,but it does not affect the positive results.

Correlation between serological screening of human T-lymphotropic virus antibodies and confirmatory tests / 中国输血杂志

【Objective】 To explore the correlation between serological screening of human T-lymphotropic virus antibodies (anti HTLV) and Western blot(WB) confirmatory tests among blood donors, so as to explore the infection status of HTLV Ⅰ/Ⅱ in Guangzhou. 【Methods】 The anti HTLV Ⅰ/Ⅱ enzyme-linked immunosorbent assay(ELISA) kit was used to screen voluntary blood donors from Guangzhou Blood Center from July 2016 to August 2022. WB was used to confirm 395 reactive blood samples by ELISA. The correlation between the S/CO values of anti HTLV Ⅰ/Ⅱ ELISA reagents and the confirmatory test was analyzed using ROC curves. 【Results】 The results showed that 25 out of 395 initially screened reactive blood donor samples were confirmed as HTLV positive by WB, while 16 were uncertain. ROC curve analysis showed a correlation between the S/CO values by ELISA and the confirmatory test results: the S/CO value at the highest Youden index was 3.789, which was the optimal threshold. The S/CO value had a certain correlation with the predicted positive rate of confirmatory results (P<0.05): the larger the S/CO value, the higher the predicted positive value. The overall prevalence of HTLV in Guangzhou is relatively low. 【Conclusion】 The prevalence of HTLV among blood donors in Guangzhou is low.Since the false positive rate of HTLV Ⅰ/Ⅱ antibody by ELISA serological screening is high, the confirmatory testing is particularly important.

HBsAg high S/CO negative samples : A comparative analysis between nucleic acid minipool test and individual test / 中国输血杂志

【Objective】 To compare the results by minipool and individual NAT on blood samples with HBsAg detection S/CO value between 0.25-0.90 by ELISA, in order to re-evaluate the safety of NAT for such negative samples with high HBsAg S/CO value and provide references for the optimization of detection process. 【Methods】 A total of 30 blood samples which were non-reactive for HBsAg by ELISA twice and with the S/CO value of any reagent between 0.25-0.90 (defined as " high S/CO value negative" ) from our center from February to October 2020 were collected, and minipool test of 6 samples and individual test were performed in parallel. 11 samples which were negative by minipool tests but positive by individual test were submitted to repeated NAT minipool tests, and the results of each test were recorded and analyzed. 【Results】 The median S/CO values of the 30 samples by two ELISA reagents were 0.565 and 0.320, respectively, and the differences were statistically significant (P 0.05). 【Conclusion】 The NAT-yield of samples with high ELISA HBsAg S/CO value was high in individual test and low in minipool test, and the NAT-yield in minipool test could be improved by repetitive test. Therefore, the safety of NAT for samples with high HBsAg S/CO value should be re-evaluated as minipool test is dominant in blood stations. Individual NAT test is recommended for such samples currently as there is no any other more sensitive detection approaches.

A retrospective analysis of 2 728 HIV antibody screening positive samples / 公共卫生与预防医学

Objective To analyze the positive results of HIV antibody screening in the laboratory of AIDS confirmation center of Hubei Provincial Center for Disease Control and Prevention from 2014 to 2020, and to provide a basis for improving detection strategies. Methods A total of 2 728 primary screening positive specimens received by the laboratory of Hubei confirmation center from 2014 to 2020 were retested with two reagents. Specimens with at least one reactive result were confirmed with western blot (WB). The samples with uncertain or negative WB results were further confirmed by nucleic acid quantitative detection. The test results were analyzed retrospectively. Results A total of 2 297 specimens with positive retest results were confirmed by WB, with a positive rate of 93.47%. The highest proportion of patients was from medical institutions. The positive rate detected by 4 diagnostic kits was apparently higher in S/CO＞10 cases than that in S/CO≤10, and the difference was statistically significant (P 5 000cps / ml, and 12 cases were TND. 13 of the 30 WB negative samples had nucleic acid test results＞5 000CPs/mL . Conclusions The coverage of HIV screening laboratories in hospitals at all levels should be further increased to find more HIV infected persons. The anti-HIV ELISA S/CO ratio is correlated with the positive results confirmed by western blot. Therefore, ELISA S/CO ratio can be used to predict anti-HIV antibody positivity. For samples with uncertain or negative WB detection, supplemental nucleic acid test should be carried out timely for early diagnosis.

Analysis of Reentry Test for the Donors Showing Reactivity or Grey Zone in a HBV Surface Antigen Assay by a Chemiluminescent Immunoassay / 대한수혈학회지

BACKGROUND: If donors who were deferred due to the reactivity or grey zone in HBV surface antigen (HBsAg) assay want to donate blood again, they need to pass reentry tests. On the other hand, approximately half of the donors who are subject to the reentry tests cannot be reentered. This study examined the association between the sample to cutoff (S/Co) value of the HBsAg assay and the final results of the reentry test. METHODS: This study analyzed the S/Co values of the HBsAg assay and the final results of the reentry tests for the 3,947 donors from January 2008 to December 2017 using the database of Blood Information Management System of the Korean Red Cross. RESULTS: 1,767 donors (44.8%) were not reentered among 3,947 deferred donors. Among 1,585 donors showing ≥10 of the S/Co value in the HBsAg screening test, 1,542 donors (97.3%) were not reentered. The additional reentry tests were performed on 120 donors who were not reentered in the first reentry test; 98 donors (81.7%) were still not reentered. Overall, 4.6% of the donors showing a grey zone in the HBsAg assay were not reentered. CONCLUSION: The reentry test needs to be restricted for the deferred donors showing a more than 10 S/Co value. The application of the grey zone of current HBsAg assay will need to be continued to enhance the HBV-related blood safety.

The Correlation between the S/CO Ratio of Anti-HCV ELISA, and the Results of the RIBA and RNA Test / 대한수혈학회지

BACKGROUND: Recombinant immunoblot assay (RIBA) or RNA test is considered to be a supplemental test for confirming a HCV infection. A correlation has been reported between the signal-to-cutoff (S/CO) ratios of a third generation HCV enzyme-linked immunosorbent assay (ELISA) and a confirmed HCV infection. This study examined the results of an evaluation of domestic anti-HCV EIA and immunoblot kit (RIBA) in Korean donors. METHODS: A total of 375,576 donor samples were tested for anti-HCV using the LG third generation HCV ELISA (LG HCD 3.0 TMB, LGphD, Korea) and HCV RNA by NAT (Biomerieux/Roche RT-PCR, 24 pool). The anti-HCV repeat reactive samples were further tested by third generation RIBA (LG HCD Confirm, LGphD, Korea). A positive result by either the nucleic acid amplification test (NAT) or RIBA was interpreted as a confirmed HCV infection. RESULTS: There were 506 out of the 375,576 donor samples (0.13%) that were anti-HCV repeat reactive (RR) by routine screening ELISA. The confirmed HCV prevalence in the donors was 0.01% (RIBA 42/375,570, RNA 36/375,570). 443 samples from the 506 repeat reactive samples in ELISA (87.6%) showed a S/CO ratio 3.6 (mean 4.40+/-0.80), compared with the negative group (mean 1.54+/-0.64). CONCLUSION: There was a good correlation between a high S/CO ratios and a confirmed HCV infection. In addition, samples showing a low S/CO ratio with an ID (Indeterminate) or negative RIBA result suggest a high probability of nonspecific reactivity in ELISA.