Evaluation of the Abbott ARCHITECT Toxo IgM assay

Development of the ARCHITECT Toxo IgM assay has been done to assist the clinician in acute Toxoplasma gondii infection detection, especially in pregnant women. Its use, in conjunction with ARCHITECT Toxo IgG and Toxo Avidity assays, will provide an array of assays particularly useful in the monitoring of pregnant females to determine the risk of maternal transmission of the parasite. Specificity results from 2 testing sites, using populations of pregnant females, hospital patients, and blood donors, demonstrated that the assay has an overall resolved relative specificity of 99.89% (confidence interval, 99.68–99.98%). Relative specificity for pregnant female specimens was 99.95% (n = 2031). Excellent seroconversion sensitivity was observed for the ARCHITECT Toxo IgM assay, which was similar to the Abbott AxSYM Toxo IgM assay (Abbott Laboratories, Abbott Park, IL). In more than 90% of the panels tested, the 1st bleed detected in the serial bleeds was the same for both assays.     

Comparative evaluation of the ARCHITECT Toxo IgG, IgM, and IgG Avidity assays for anti-Toxoplasma antibodies detection in pregnant women sera

We assessed the performance of the ARCHITECT Toxo IgG, IgM, and IgG Avidity assays against corresponding assays on AxSYM and Vidas using 730 sera from pregnant women. The ARCHITECT Toxo IgG and IgM assays showed a relative sensitivity of 97.5% and 89.9% and a relative specificity of 99.1% and 99.8%, respectively. If IgM sensitivity is calculated only for sera drawn less than 4 months after infection, the relative sensitivity rises to 98.1%. Correlation between the ARCHITECT and Vidas Avidity assays was 0.87 (n = 103). Testing 86 IgG-positive specimens from recent infection (<4 months), we never obtained high avidity results, but 2 specimens were in the gray zone, whereas sera from past infections (>4 months) exhibited high avidity results in 72.5% (137/189) of cases. The method can be used reliably to exclude recent infections in sera with concurrently positive results for IgM and IgG (IgG, >3 IU/mL).     

A new human IgG avidity test,using mixtures of recombinant antigens (rROP1, rSAG2, rGRA6), for the diagnosis of difficult-to-identify phases of toxoplasmosis

The preliminary diagnostic utility of two mixtures of Toxoplasma gondii recombinant antigens (rROP1+rSAG2 and rROP1+rGRA6) in IgG ELISA and IgG avidity test has been evaluated. A total of 173 serum samples from patients with toxoplasmosis and seronegative people were examined. The sensitivity of IgG ELISA for rROP1+rSAG2 and rROP1+rGRA6 was 91.1% and 76.7%, respectively, while the reactivity for sera from patients where acute toxoplasmosis was suspected was higher, at 100% and 95.4%, respectively, than for people with chronic infection, at 88.2% and 70.6%. In this study a different trend in avidity maturation of IgG antibodies for two mixtures of proteins in comparison with native antigen was observed. The results suggest that a new IgG avidity test using the mixtures of recombinant antigens may be useful for the diagnosis of difficult-to-identify phases of toxoplasmosis. For this reason, selected mixtures after the additional tests on groups of sera with well-defined dates of infection could be used as a better alternative to the native antigens of the parasite in the serodiagnosis of human T. gondii infection.     

风疹病毒特异性IgG抗体亲和力测定的临床意义

目的区分风疹病毒原发性感染、继发性感染的病毒活化或再感染。方法对12 y以下患儿的风疹病毒IgG抗体(RV-IgG)阳性血清,采用尿素变性酶联免疫吸附实验(ELISA法)测定RV-IgG抗体亲和力指数(AI)。结果1~12 y的患儿中,只有4.8%(3/63)的病例有低亲和力抗体(AI<30%)。1 y以内患儿中高达56.2%(18/32)的病例有低亲和力抗体,明显高于1~12 y患儿。1 y以内患儿中,1~3 mo和4~6 mo患儿低亲和力抗体比例低(分别为36.4%和44.4%),而7~12mo患儿有83.3%为低亲和力抗体。结论RV的早期感染大都发生在1y以内。IgG抗体亲和力测定是鉴别初次感染和体内病毒活化及再感染的有效方法。     

Evaluation of the Abbott ARCHITECT Chagas prototype assay

Serologic tests are established tools for the diagnosis of Chagas disease applied to support a safe blood supply in endemic countries. However, sensitivity and specificity of most commercially available enzyme-linked immunosorbent assays (ELISAs) are not regarded as adequate enough to rely on a single assay to determine the Trypanosoma cruzi infection status of a blood donor or a patient. The overall assay performance is driven by the general choice of antigens and the actual antigen cocktail provided in the test. In this report we describe key performance data of the Abbott ARCHITECT Chagas prototype assay in comparison to the well-recognized bioMérieux ELISA cruzi assay. The ARCHITECT assay demonstrated superior specificity (99.99% versus 99.93%) and sensitivity (99.85% versus 98.38%), along with excellent precision, thus showing the potential to serve as single assay to determine the T. cruzi status of a given blood unit or diagnostic specimen on a fully automated instrument platform.     

Combination of line immunoassays Mikrogen recomLine CMV IgG and recomLine CMV IgG Avidity helps to date the onset of CMV primary infection

CMV IgG avidity assays are widely used and can be helpful in pregnant women to date the onset of CMV primary infection; however, these tests are not standardized and sometimes give inconclusive results. We evaluated the performances of Mikrogen recomLine CMV IgG and IgG Avidity compared to the VIDAS CMV IgG Avidity. On a first sample set of 89 sequential sera collected from 40 women with precisely determined onset of CMV primary infection, the combination of Mikrogen recomLine CMV IgG and IgG Avidity showed an accurate interpretation in 83.1% (74/89), an incorrect result in 4.5% (4/89), and an inconclusive result in 12.4% (11/89) and showed a better sensitivity to diagnose infections <14?weeks compared to VIDAS (85.9% vs. 76.9%). On a second sample set of 89 sera with an intermediate VIDAS CMV IgG Avidity, the combination of line immunoassays provided additional information on the time of infection in 79% (70/89) of the samples. This combination of line assays is useful as additional confirmatory testing and can help to date more precisely the onset of CMV primary infection.     

Comparative evaluation of the new ARCHITECT EBV assays considering different testing algorithms

In the current evaluation, Epstein-Barr virus (EBV) serology was performed on 1113 routine serum samples. Although the initial request for all samples from the general practitioner was EBV IgM testing, 80.9% were classified as past infections. The ARCHITECT^® viral capsid antigen (VCA) IgM, VCA IgG, and EBV nuclear antigen (EBNA) 1 IgG assays showed good results for sensitivity and specificity, being 100.0%, 98.3%, and 100.0% and 99.9%, 95.4%, and 99.6%, respectively. Using an algorithm based on initial EBNA-1 IgG testing, followed by VCA IgG and IgM for samples that were not EBNA-1 IgG reactive, the number of tests per sample could be reduced to nearly 50% compared to parallel testing. The high sensitivity and specificity of the ARCHITECT^® EBNA-1 IgG assay in combination with a low number of grayzone results are a precondition for the chosen test algorithm. Thus, the newly developed ARCHITECT^® EBV panel is suitable for accurate and cost-efficient EBV serology in a routine clinical laboratory.     

Evaluation of the Roche Elecsys Toxo IgG and IgM electrochemiluminescence immunoassay for the detection of gestational Toxoplasma infection

Unidentified gestational infection with Toxoplasma gondii may lead to fetal infection with severe complications later in childhood. Because diagnosis of maternal infection solely depends on serology, routine tests with high sensitivity and specificity are required. In this study, the new Roche Elecsys Toxo IgG and IgM immunoassay was compared with Sabin-Feldman dye test and immunosorbent agglutination assay-IgM as reference test. Serum samples were analyzed from 927 pregnant women, including 100 negative, 706 chronic, and 121 acute infections. The combination of both Elecsys IgG and IgM assays demonstrated high sensitivity and specificity of 97.1% and 100.0%, respectively, and a positive and negative predictive value of 100.0% and 81.3%, respectively. The Elecsys assay is a useful tool as a first-line screening method to detect gestational infections. However, if gestational infection is assumed, confirmatory testing by a reference laboratory might be necessary to discriminate between pre- and postconceptional infection to start antiparasitic treatment to avoid mother-to-fetus transmission and severe sequelae.     

Use of SAG2A recombinant Toxoplasma gondii surface antigen as a diagnostic marker for human acute toxoplasmosis: analysis of titers and avidity of IgG and IgG1 antibodies

We evaluated the reactivity of IgG and IgG1 antibodies by immunoassays in sera from patients with acute and chronic phases of toxoplasmosis against 2 recombinant antigens, SAG2A (full molecule) and SAG2ADelta (truncated molecule from the epitope recognized by A4D12 monoclonal antibody [mAb]), in comparison with soluble Toxoplasma antigen (STAg). Results demonstrated higher IgG reactivity in acute sera with both STAg and SAG2A than in chronic phase sera, and this difference was more evident for IgG1 antibodies to SAG2A. Low reactivity to SAG2ADelta was found in sera from both phases. ELISA-IgG-SAG2A showed high sensitivity (95%) and specificity (100%). ELISA-IgG1-SAG2A sensitivity was significantly higher (90%) for acute than for chronic (67%) phases. ELISA-IgG avidity using STAg demonstrated high performance for characterizing sera with high avidity (>60%), whereas the ELISA-IgG1 avidity-SAG2A immunoassay was the best to define chronic phase infection. It can be concluded that SAG2A is an antigen that may be used as a diagnostic tool to characterize the acute phase Toxoplasma gondii infection. Also, the epitope recognized by A4D12 mAb may be critical for the recognition of this molecule.     

Performance characteristics of the Euroimmun enzyme-linked immunosorbent assay kits for Brucella IgG and IgM

Brucella IgG and IgM ELISA kits manufactured by Euroimmun (Lubeck, Germany) were evaluated in a reference laboratory setting. Intraassay coefficient of variation (CV) values were ≤10% for positive sera and ≤12% for negative sera; interassay CVs were ≤12% for positive sera and ≤20% for negative sera. The tube agglutination test (TAT) was performed on 51 sera exhibiting various ELISA reactivity profiles. All 18 sera negative for both IgG and IgM by ELISA were TAT negative (titer <1:80), whereas 31 (94%) of 33 sera positive for IgG and/or IgM were TAT positive; the 2 discordant sera were IgG positive IgM negative by ELISA. None of 41 sera from healthy laboratory employees were ELISA IgG positive, whereas 1 (2%) of 41 was ELISA IgM positive. Similarly, 0 of 149 potentially cross-reactive sera (containing rheumatoid factor or antibodies to selected Gram-negative bacteria) was ELISA IgG positive, whereas 4 (3%) of 149 were ELISA IgM positive. These findings demonstrate the acceptable performance of the Euroimmun ELISAs for Brucella antibodies.     

Performance evaluation of serum IgG subclass quantification using a SPAPLUS turbidimetric analyzer and comparison with the BNII nephelometer

Abstract

IgG consists of four subclasses: IgG1, IgG2, IgG3, and IgG4. Changes in the serum concentration of each subclass reflect different clinical situations, and quantification of each subclass is important to assess patients’ clinical states. Herein, we evaluated the analytical performance of the SPAPLUS turbidimetric analyzer (The Binding Site, Birmingham, UK) for IgG subclass. Precision, linearity, comparison with the BNII system (Siemens Healthineers, Erlangen, Germany), and reference interval were assessed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. The repeatability and within-laboratory precision were within 5% for all IgG subclasses. The coefficient of determination (R²) was higher than 0.99 for the analytical measurement range in all IgG subclasses. Comparison between SPAPLUS and BNII revealed significant differences in IgG1, IgG3, and IgG4 (p?相似文献   

Total IgG method insensitivity to the presence of IgG4 immunoglobulins

Objective

IgG4 related disease (IgG4RD) is detected in part by measurement of serum IgG4 levels in patients suspected to have the condition. The immunonephelometric methods that are used to measure serum IgG4 are susceptible to hook effect errors. The quality control parameter IgGRDiff = 100 ∗ [Sum (IgG1, IgG2, IgG3, IgG4) − Total IgG] / Average [Sum (IgG1, IgG2, IgG3, IgG4), Total IgG] is theoretically of use in detecting large IgG4 hook effect. We evaluated the IgGRDiff parameter in this context.

Design and methods

Retrospective review of the IgGRDiff parameter in a cohort of patient samples. All samples were tested with the Siemens BNII analyzer utilizing Siemens (total IgG) and Binding Site (IgG subclass) reagents. The 95th percentile for the absolute value of IgGRDiff was determined and compared to the IgGRDiff values for the samples with known hook effect error. IgGRDiff was regressed against IgG4Rsum [IgG4Rsum = 100 ∗ IgG4 / (IgG1 + IgG2 + IgG3 + IgG4)].

Results and discussion

The 95th percentile of the absolute value of the IgGRDiff parameter was 22.8% in our study sample set (n = 163). The absolute value of the IgGRDiff was < 22% in 4/6 cases indicating low sensitivity of IgGRDiff in identifying IgG4 hook effect errors. IgG4Rsum was directly correlated with IgGRDiff (IgGRDiff = 1.21 ∗ IgG4Rsum − 7.9, R² = 0.62) indicating that the total IgG measurement has little or no reactivity with IgG4 immunoglobulins.

Conclusions

The Siemens’ Total IgG method is insensitive to IgG4 and should not be used as a quality control parameter to detect IgG4 hook effect.     

HBsAg blood screening and diagnosis: performance evaluation of the ARCHITECT HBsAg qualitative and ARCHITECT HBsAg qualitative confirmatory assays

A low initial reactive rate for screening assays is important for time- and cost-effective infectious disease testing. Therefore, the new ARCHITECT HBsAg Qualitative screening assay, in conjunction with the new ARCHITECT HBsAg Qualitative Confirmatory assay, was introduced. As the role of hepatitis B surface antigen (HBsAg) as surrogate marker for HBV resolution and the monitoring of drug effectiveness are becoming increasingly important, the established ARCHITECT HBsAg Quantitative assay remains available on the market. Precision, sensitivity, and specificity of the newly developed screening assay were in the range of established HBsAg assays. Seroconversion sensitivity was slightly superior compared to other commercially available assays. An initial reactive rate of 0.2% (without HBsAg-confirmed positive samples of 0.17%) for the ARCHITECT HBsAg Qualitative assay was observed. As the new screening assay is a 1-step assay format, the "high-dose hook effect" was investigated to assess the risk of false-negative results, but even very high positive HBsAg samples obtained signals clearly above the cutoff.     

头颈部IgG4相关性疾病的临床及MRI诊断

目的:探讨头颈部IgG4相关性疾病的MRI诊断和临床分析,提高其诊断及鉴别诊断。方法:对我院12例头颈部IgG4相关性疾病的MRI资料进行回顾性研究,结合其临床表现进行分析。结果:所有患者均有血清IgG4升高,其中手术病理6例,6例皮质类固醇激素治疗病灶缩小;12例中,包括局限性硬化性硬脑膜炎4例,垂体炎3例,双侧颌下腺炎3例,双侧泪腺炎2例;其中3例同时累及三叉神经。结论:头颈部IgG4相关性疾病的MRI表现有一定特征性,结合临床及IgG4升高,可以提高对疾病的认识。     

柴桂合剂对反复呼吸道感染患儿血浆促炎症细胞因子、IgG亚类的影响

目的：探讨柴桂合剂对反复呼吸道感染患儿（RRTI）血浆促炎症细胞因子（PIC）及IgG亚类的影响。方法：采用酶联免疫吸附试验（EuSA）检测RRTI患儿急性期和柴桂合剂治疗后血浆IL-6、IL-8、TNF-α和IgG亚类等指标的变化，并与正常对照组比较，部分指标间行直线相关分析。结果：RRTI组急性期血浆IL-6、IL-8、TNF-α、IgG1均值较正常对照组明显升高；IgG亚类缺陷检出率为33．33％。柴桂合剂治疗后RRTI组血浆IL-6、TNF-a均值明显降低，但仍高于正常对照组；IL-8无显著变化；IgG1均值则较急性期明显升高；IgG亚类缺陷纠正率达78．57％。结论：IL-6、IL-8、TNF-α在RRTI发病过程中可能起重要作用；柴桂合剂可能具有抑制RRTI患儿PIC产生和提高血浆IgGl水平的作用。     

Avidity and positive allosteric modulation/cooperativity act hand in hand to increase the residence time of bivalent receptor ligands

Bivalent ligands bear two target‐binding pharmacophores. Their simultaneous binding increases their affinity (avidity) and residence time. They become ‘bitopic’ when the binding sites at the target permit the pharmacophores the exert allosteric modulation of each other's affinity and/or activity. Present simulations reveal that positive cooperativity exacerbates these phenomena, whereas negative cooperativity curtails them, irrespective of whether the association or dissociation rates of the individual pharmacophores are affected. Positive cooperativity delays the attainment of equilibrium binding, yielding ‘hemi‐equilibrium’ conditions and only apparent affinity constants under usual experimental conditions. Monovalent ligands that bind to one of the target sites decrease the bitopic ligand's residence time concentration‐wise; their potency depends on their association rate and thereon acting cooperativity rather than on affinity. This stems from the repetitive, very fast reformation of fully bound bitopic ligand‐target complexes by rebinding of freshly dissociated pharmacophores. These studies deal with kinetic binding properties (of increasing interest in pharmacology) of bitopic ligands (a promising avenue in medicinal chemistry).     

ABO新生儿溶血病与O型孕妇血清中IgG及其亚类含量的相关分析

目的探讨O型孕妇血清IgG抗体及其亚型含量与新生儿溶血病(HDN)的关系。方法采用血型血清学方法,对317名夫妇血型不合的O型孕妇作IgG抗体效价检测,并对其中有妊娠史的287名孕妇作IgG抗体水平比较;采用ELISA法对71名HDN患儿及其母亲、65名健康O型孕妇和51名健康新生儿的IgG亚类作定量分析。结果1)317名新生儿中发生ABOHDN71例(22.4%),其中抗-A46例、抗-B25例;2)随着妊娠次数的增加,IgG抗体效价≥64者的比例和ABO-HDN发病率升高,>2次妊娠与第2次妊娠间有统计学差异;3)患儿及其母亲体内IgG抗体的含量显著高于正常对照组,且以IgG1抗体为主,患儿体内的IgG1比例(61.9%)高于母体(52.8%)。结论新生儿ABOHDN的发病率随其母亲体内IgG抗体效价的升高而升高,且与母亲体内IgG1呈正相关。夫妇血型不合的O型孕妇应定期检测IgG抗体及其亚类含量。     

幽门螺旋杆菌IgG抗体及现症感染条带(CIM)蛋白抗体联合检测在健康查体人群中的临床应用

目的探讨采用胶体金幽门螺旋杆菌IgG抗体和现症感染条带蛋白抗体联合检测在健康查体人群中的临床应用价值,了解查体人群HP现症感染情况及治疗依据。方法采用采胶体金幽门螺旋杆菌IgG抗体和现症感染条带蛋白抗体联合检测试剂盒对1 434名查体者进行HP感染检测,并对HP阳性者随机抽样进行组织学检查以明确诊断,并对两种方法检测结果进行统计学分析。对现正感染者进行内科规范治疗后再次做现正感染条带的复检。结果健康查体人群HP感染率为58.2%,CIM线感染检出率98.4%,组织学检查感染检出率98.8%,二者差异无统计学意义(P0.05),男女检出率二者无显著差异(P0.05)。治疗后CIM线消失或减弱说明有效率为89%。结论采用胶体金幽门螺旋杆菌IgG抗体和现症感染条带蛋白抗体联合检测适合各级医院大规模查体需要,也可作为现正感染者的对症治疗依据和疗效观察,具有较高的临床应用价值。     

Current status of available standards for quality improvement of assays for detection of autoantibodies to nuclear and intracellular antigens

Considerable progress has been made in the improvement of clinical assays for the detection of autoantibodies to nuclear and intracellular antigens with the use of available World Health Organization (WHO) and Arthritis Foundation/Centers for Disease Control (AF/CDC) standards. The ultimate goal of standardization is for various clinical laboratory test results to be interchangeable and for an exchange of data to be done with confidence. This report discusses the available standards. In addition, significant technical problems and variations in methodologies for the detection of autoantibodies to intracellular antigens noted during a 4-year study by a European Consensus Study Group are detailed. Currently, there is a need for a future generation of reference preparations and standards that will show specific antibody reactivity on sensitive enzymes and immunoblotting assays. Standardization efforts should be done to characterize specific nuclear and cellular antigen preparations that may be of natural or of recombinant technology origin. © 1994 Wiley-Liss, Inc.