[Analysis of Reasons Causing False Positive of HBsAg Single-ELISA-Reactive in Blood Donors].

OBJECTIVE: To explore the reasons causing the false positive of HBsAg single-ELISA-reactive in blood donors of Jiangsu province so as to provide reference data for the return of blood donors. METHODS: Serological test: HBsAg ELISA parallel detection was performed on 319 444 samples of blood donors from 2014 to 2017; the ECLIA was employed to confirm the single-ELISA-reactive (S/CO≥0.5) samples, the nucleic acid test was used to detect the HBV DNA on the all single-ELISA-reactive samples in 6/8 people mixed/single. Reagent evaluation: the Receiver-Operating-Characteristic curve (ROCC) was drawn by the ECLIA/NAT results as the gold standard, and the diagnostic performance of reagents A and B under different cut-off was evaluated. RESULTS: A total of 227 (0.71‰) single-ELISA-reactive samples were detected among 319 444 blood donors, including 39 cases (17.2%) of positive HBsAg and 12 cases (5.3%) of positive HBV DNA; Under the maximum YI, the COI (1.0) employed by the manufacturer recommendation has a better diagnostic value than laboratory COI (0.5), and the capability of reagent A was better than that of reagent B (AUC: 0.661 vs 0.632; Youden: 0.329 vs 0.297), but the specificity of both reagents was restricted (＜60%). Under the maximum YI, the best cut-off value of reagents A and B were 2.4 and 1.4 COI, respectively. Compared with the cut-off value of manufacturer, the sensitivity of reagents A decreased by 33% and the false positive rate decreased by 60% while the sensitivity of reagent B increased by 140% and the false positive rate increased by 36%, respectively. CONCLUSION: The false positive of HBsAg single-ELISA-reactive in blood donors is caused by the limited specificity of ELISA reagent and the setting of COI values. According to ROCC maximum YI method, the COI can be set as 2.4 COI and (0.5-1.4) COI for reagent A and B to reduce false positive rate.

Selective malaria antibody screening among eligible blood donors in Jiangsu, China.

The risk of transfusion-transmitted malaria is a major concern in many countries. This study investigated the prevalence of malaria antibodies and parasitemia in eligible blood donors in Jiangsu, in Eastern China. Malaria antibodies were detected in 2.13% of the 704 plasma samples studied. We found that the prevalence of malaria antibodies was not significantly correlated with gender, occupation and frequency of donation, but it increased with age. No Plasmodium was observed in red blood cells and no Plasmodium DNA was detected in any of the antibody-positive samples. The prevalence of malaria antibodies was not higher than expected in Eastern China.

A facile method to prepare high-performance magnetic and fluorescent bifunctional nanocomposites and their preliminary application in biomolecule detection.

Magnetic and fluorescent bifunctional nanocomposites have great potential in biomolecule detection and biological imaging applications. So far, it remains a challenge to prepare bifunctional nanocomposites with high colloidal and fluorescent stability. To address this problem, we utilized a simple ring-opening reaction to conjugate Fe3O4 and CdZnSeS quantum dots (QDs). The surface amine groups of SiO2-coated Fe3O4 nanoparticles (Fe3O4@SiO2) opened the rings of the surface maleic anhydride groups of poly(styrene-co-maleic anhydride)-coated CdZnSeS QDs (QDs@PSMA), and then the resulting nanocomposite was functionalized with Jeffamine M-1000 polyetheramine (JMP) by a ring-opening reaction. The structures and properties of the bifunctional nanocomposites were fully characterized by transmission electron microscopy, dynamic light scattering, spectrofluorometry and vibrating sample magnetometry. The results indicated that the nanocomposites prepared by the conjugation method had dramatically higher quantum yields (QYs) than those prepared by the SiO2 co-encapsulation method. After introducing JMP, the nanocomposites exhibited high fluorescent and colloidal stability over a wide pH range (pH 2-13), a low level of protein adsorption in PBS with 10% fetal bovine serum at 37 °C, and a negligible level of nonspecific binding when incubated with HeLa cells. Sandwich fluoroimmunoassay results indicated that the nanocomposites can be successfully applied in a variety of diagnosis and bioimaging applications.

Quantum dot-based immunochromatography test strip for rapid, quantitative and sensitive detection of alpha fetoprotein.

Rapid, quantitative detection of tumor markers with high sensitivity and specificity is critical to clinical diagnosis and treatment of cancer. We describe here a novel portable fluorescent biosensor that integrates quantum dot (QD) with an immunochromatography test strip (ICTS) and a home-made test strip reader for detection of tumor markers in human serum. Alpha fetoprotein (AFP), which is valuable for diagnosis of primary hepatic carcinoma, is used as a model tumor marker to demonstrate the performance of the proposed immunosensor. The principle of this sensor is on the basis of a sandwich immunoreaction that was performed on an ICTS. The fluorescence intensity of captured QD labels on the test line and control line served as signals was determined by the home-made test strip reader. The strong luminescence and robust photostability of QDs combined with the promising advantages of an ICTS and sensitive detection with the test strip reader result in good performance. Under optimal conditions, this biosensor is capable of detecting as low as 1 ng/mL AFP standard analyte in 10 min with only 50 µL sample volume. Furthermore, 1000 clinical human serum samples were tested by both the QD-based ICTS and a commercial electrochemiluminescence immunoassay AFP kit simultaneously to estimate the sensitivity, specificity and concordance of the assays. Results showed high consistency except for 24 false positive cases (false positive rate 3.92%) and 17 false negative cases (false negative rate 4.38%); the error rate was 4.10% in all. This demonstrates that the QD-based ICTS is capable of rapid, sensitive, and quantitative detection of AFP and shows a great promise for point-of-care testing of other tumor markers.