Evaluation of a new automated assay for hepatitis B surface antigen (HBsAg) detection VIDAS HBsAg Ultra

In a multicenter study a new automated screening assay, VIDAS HBsAg Ultra (long (L) and short (S) incubation protocol (Biomérieux, Marcy l'Etoile, France), was compared to a well established test (AxSYM HBsAg v2, Abbott Diagnostics, Wiesbaden, Germany) for the detection of hepatitis B virus (HBV) surface antigen (HBsAg). A total of 32 seroconversion panels, sera from the chronic phase of infection, dilution series of the WHO standard, S gene mutants (recombinant mutants and diluted and undiluted sera harbouring mutants with single or multiple amino acid (aa) substitutions, n = 40) and isolated anti-HBc positive samples were tested for the evaluation of sensitivity. Sera from HBsAg negative blood donors, pregnant women, hospitalized patients and potentially cross-reactive samples were investigated to determine the specificity of the new assay. The VIDAS HBsAg Ultra (L+S) had a higher sensitivity than the alternative assay for the detection of acute hepatitis B in seroconversion panels. The mean time of the diagnostic window was shortened with the VIDAS HBsAg Ultra (L) and (S) in comparison with the AxSYM HBsAg v2 by 1.06 and 0.66 days, respectively. The VIDAS HBsAg Ultra (L) did not detect one diluted sample out of six bearing the single aa G145R substitution, and two out of 12 diluted samples harbouring multiple aa substitutions. The analytical sensitivity of the assays varied from one surface mutant to another. While no false positive results were obtained with the VIDAS HBsAg Ultra (L+S) among potentially interfering samples, four false positives were detected with the AxSYM HBsAg v2. The respective values for sensitivity for the VIDAS HBsAg Ultra (L), (S) and the AxSYM HBsAg v2 were 99.07%, 97.87% and 94.14%. The specificities were 100% (VIDAS HBsAg Ultra L and S) and 99.6% (AxSYM HBsAg v2). In conclusion, the VIDAS HBsAg Ultra is highly sensitive and specific and represents an improvement for the detection of HBsAg in routine diagnostic laboratories.     

Multicenter evaluation of Xpert HIV-1 viral load assay for HIV quantification in China

New approaches to increase HIV-1 testing and HIV-1 viral load (VL) monitoring are needed for people living with HIV (PLHIV) in China. The Xpert HIV-1 VL assay was prequalified by the World Health Organization in 2017 but has not been evaluated in China. A multicenter evaluation was conducted to assess the accuracy of the Cepheid Xpert HIV-1 VL assay compared to the Abbott RealTime HIV-1 assay in China. Overall agreement was seen in 558 of 562 specimens (99.29%) with a κ value of 0.962. Pearson's coefficient between the two assays was 0.943. Analyzed by the Bland-Altman method, the mean bias was −0.54 log₁₀ copies/mL, and 94.05% results fell within the 95% confidence limit of agreement (−1.248 to 0.168 log₁₀ copies/mL). The coefficient of variation of the Cepheid Xpert HIV-1 VL assay ranged from 0.61% to 1.55%, as determined by testing eight positive plasma specimens with three different lots on different days. Due to its simplicity, random-access, rapid turnaround time, and accuracy, the Xpert HIV-1 VL assay can be used in local hospitals and clinics that bear the burden of identifying and treating HIV patients in China.     

Multicenter evaluation of the NucliSens EasyQ HIV-1 v1.1 assay for the quantitative detection of HIV-1 RNA in plasma

The Nuclisens EasyQ HIV-1 v1.1 assay (Biomerieux) is a real-time detection method combined with NASBA technology designed to measure plasma HIV-RNA. Its performance was assessed in 1008 clinical specimens collected from individuals infected with clade B (774) and non-B (234) HIV-1 variants at four European laboratories. The results were compared with those obtained using three other commercial viral load assays: Cobas Amplicor Monitor HIV-1 v1.5 (Roche), Versant HIV-1 RNA assay (Bayer) and Nuclisens HIV-1 QT (Biomerieux). Overall, the linearity, specificity and reproducibility of the EasyQ assay was comparable with that from the other tests. The correlation coefficient (R) between methodologies was 0.85 for Amplicor; 0.87 for Versant; and 0.91 for Nuclisens. The specificity of the assay was 99.4%. Of note, Versant missed 17% of specimens with non-B subtypes which could be detected by EasyQ, while Amplicor provided similar results than EasyQ. HIV-1 group O specimens were only detected by the EasyQ assay. In conclusion, the performance of the EasyQ assay seems to be similar to that of other HIV-1 viral load tests currently on the market, but it is more sensitive than Versant for HIV-1 non-B subtypes and shows a wider dynamic range than Amplicor. Moreover, as it incorporates the advantage of real-time detection procedures, it facilitates high throughput and short turnaround time.     

Enzyme-linked immunosorbent assay for detection of human antibodies to Salmonella typhi Vi antigen

An enzyme-linked immunosorbent assay (ELISA) was developed to detect antibodies to Salmonella typhi Vi antigen in human serum, and the results were compared with those from a previously described hemagglutination assay (HA). The ELISA detected Vi antibodies at a titer of greater than or equal to 20 in 40 (52%) of 77 sera from typhoid fever patients, whereas the HA gave titers of greater than or equal to 20 in 35 (47%). Determination of titers of serum specimens from 170 persons without typhoid fever revealed Vi antibody titers of greater than or equal to 20 in 4 (2.3%) by the ELISA and 3 (1.7%) by the HA. Unlike the sensitized erythrocytes used in the HA, the ELISA reagents have a shelf life of greater than or equal to 1 year. The ELISA may be preferred by some laboratories, especially those already performing other ELISA tests.     

Multicenter evaluation of a fully automated screening test, VIDAS HIV 1 + 2, for antibodies to human immunodeficiency virus types 1 and 2.

A multicenter study was done to evaluate the sensitivity, specificity, and efficiency of a new screening test for the simultaneous detection of human immunodeficiency virus type 1 and 2 (HIV-1 and HIV-2) antibodies. The VIDAS HIV 1 + 2 (bioMérieux, Marcy l'Etoile, France) is a fully automated enzyme-linked fluorescent immunoassay that uses synthetic peptides from immunodominant regions of gp41 of HIV-1 and gp36 of HIV-2 as antigens. A total of 2,984 samples were evaluated with this system in six different laboratories, and the results were compared to those obtained with other enzyme-linked immunosorbent assays. The VIDAS HIV 1 + 2 assay showed a very good performance in terms of sensitivity (100%) and specificity (99.6%), requiring minimal manipulation and short incubation time (32 min) to give results similar to or better than those of the other enzyme-linked immunosorbent assays used for screening.     

The immunoenzyme detection of the HIV-1 antigen by using monoclonal antibodies to protein p24]

A test system using monoclonal antibodies to HIV p24 was developed for solid-phase ELISA for detection of HIV antigen (AG) which helped detect the content of AG in samples with trace concentrations, less than 25 pg/ml. The test system can be used for AG monitoring in natural specimens (serum of HIV-infected patients and culture medium of infected cells) and for determination of antigen-recombinant product of HIV gag gene.     

Comparative evaluation of eight commercial enzyme linked immunosorbent assays and 14 simple assays for detection of antibodies to HIV

To evaluate the performance of 22 assays for the detection of antibodies to HIV. Twenty-two assays for the combined detection of antibodies to HIV-1 and HIV-2, were evaluated on the same panel of serum specimens of diverse origin. Eight of the assays were ELISAs and the remaining 14 were simple, assays read visually. The specimen panel consisted of anti-HIV positive and negative samples from Africa (n=192), Europe (n=206), Asia (n=99) and Latin America (n=98). In addition to estimations of sensitivity and specificity, the assays were assessed, using a novel scoring system, for their ease of performance and for their suitability for use in small laboratories and clinics. The sensitivities of the assays in terms of seroconversion were assessed using series of specimens collected from nine individuals undergoing seroconversion. Eight ELISAs and eight of 14 simple assays had sensitivities and specificities of >99 and 95%, respectively. The results of these evaluations will be of assistance to those responsible for the selection of appropriate anti-HIV assays according to laboratory circumstances, the purpose of the testing and the population being tested.     

重组抗原Em18双抗原夹心酶联免疫吸附试验法检测泡球蚴抗体的建立及初步评价

目的 建立双抗原夹心酶联免疫吸附试验(ELISA)检测泡状棘球蚴抗体的方法.方法 重组抗原Em18(rEm18)作为包被抗原,以辣根过氧化物酶(HRP)标记rEm18抗原为检测抗原,建立检测人血清中泡状棘球蚴抗体的双抗原夹心ELISA方法;应用方阵滴定法对包被抗原、酶标抗原等条件进行优化,并对该系统的灵敏性、特异性、重复性进行初步分析评价.结果 rEm18最佳包被浓度为2.5μg/mL,HRP标rEm18稀释度为1∶800.灵敏度为92％(46/50),特异性为94％(47/50),假阴性率为8％ (4/50),假阳性率为6％ (3/50),批内变异≤9.55％,批间变异≤14.79％,与Em2-ELISA试剂盒检测结果有良好的一致性.结论 本研究成功建立了快速检测泡球蚴特异性抗体的ELISA法,其可以用于人泡球蚴病的早期诊断.     

Salivary detection of HIV-1 antibodies using recombinant HIV-1 peptides

Salivary antibodies may play a role in the absence of HIV-1 transmission by saliva. We evaluated the presence of salivary IgG antibodies to HIV-1 using a recombinant ELISA. Whole saliva was collected from 21 HIV-1-seropositive individuals and assayed in an ELISA, ASQ (Beckman Instruments, Brea, CA), consisting of a panel of six HIV-1 recombinant peptides. Saliva samples from 20 individuals demonstrated IgG to one or more peptides and 18 to two or more peptides. Samples from 20 seropositive individuals were reactive with the gp41 peptide, whereas only 12 were reactive with the two gp120 peptides. Nineteen of twenty salivas also had detectable IgG antibodies to HIV-1 by Western blotting. The results indicate that viral-specific IgG antibodies are present in the saliva of a high percentage of HIV-infected individuals and that a recombinant peptide ELISA for saliva might be useful for the detection of HIV-1 infection.     

Spectrophotometric assay for the detection of antibodies to DNA

A spectrophotometric assay for the detection of anti-DNA antibodies in the sera of patients with various connective tissue diseases is described. The sensitivity of the method was compared with hemagglutination and enzyme-linked immunosorbent assay. The method is convenient, specific and suitable for use in clinical laboratories where facilities for radioimmunoassay do not exist.     

国产HIV-1p24抗原检测试剂盒的评价

目的探讨国产的HIV-1 p24抗原检测试剂盒进行药物筛选研究的可行性。方法对国产试剂盒的使用性能与Biomerieux公司商品化的Vironostika试剂盒进行比较,评估国产试剂盒的敏感性、重复性及检验效能。结果国产试剂盒具有较高的敏感性和重复性,在体外药效学筛选实验中国产试剂盒的阳性检出率及药物评价结果与Vironostika试剂盒差异无统计学意义(P>0.05)。结论国产试剂盒具有较好的使用特性,在药物筛选中可以用国产试剂盒替代Vironostika试剂盒。     

Assessment of the performance of a rapid, lateral flow assay for the detection of antibodies to HIV

Rapid HIV assays have recently been shown to have important applications for various testing situations, including early identification of infected individuals, to allow intervention strategies in a clinically relevant time frame. A rapid, lateral flow, HIV-1/2/O assay was evaluated using 2,000 serum or plasma samples from various risk groups and geographic locations, including HIV-1 and HIV-2 positive sera from five countries. Two U.S. Food and Drug Administration (FDA)-licensed screening assays and a FDA-licensed confirmatory assay were used as reference tests. The rapid assay exhibited a near-perfect sensitivity (99.2%) and an excellent specificity (99.9%). Moreover, its analytical sensitivity was found to be better than most FDA-licensed enzyme-linked immunosorbent assays (ELISAs), detecting infection at the same time as the most sensitive ELISA in two of five seroconversion panels, and at the same time or earlier than four of five ELISAs in all five panels. We conclude that this rapid assay is a suitable test for the detection of HIV infection that could be particularly useful in developing countries where facilities may not support the use of instrumentation.     

A preliminary evaluation of five HIV antigen detection assays

Five commercial assays for detecting HIV antigen were evaluated using a panel of 40 coded samples in six laboratories. All assays were capable of detecting HIV-1 antigen (HIV-1 Ag), and are likely to prove useful for monitoring supernatant fluids from a variety of cell cultures. The concentration of HIV-1 protein which the assays detected varied from 25 ng/ml down to 25 pg/ml. Three of the five assays were also able to detect HIV-2 Ag. More extensive evaluations are needed to determine the sensitivity and specificity of these assays on serum samples and body fluids.