Vitamin B<Subscript>12</Subscript> Immunoassay on Roche Elecsys 2010: Effects of High Excess Concentration of Serum Vitamin B<Subscript>12</Subscript> in CKD Patients on Parenteral Administration

Vitamin B₁₂ being water soluble is excreted in the urine when administered in excess. The probability of finding an abnormally excess serum concentration would be almost surreal. We report a peculiar clinical situation that may impact the vitamin B₁₂ immunoassay on the Roche Elecsys 2010 due to excess analyte concentration. In separate episodes (Feb and June 2010), the Biochemistry laboratory of a tertiary-care hospital, Kolkata, India, encountered two critically ill patients with background chronic kidney disease (CKD), low urine output, and on cyanocoabalamin supplementation, who had serum vitamin B₁₂ concentrations far exceeding expected values; even post dialysis. The B₁₂ assays (pmol/l) were performed using electrochemiluminiscence immunoassay on Roche Elecsys 2010, the assay validity confirmed by concomitant quality control runs. The immunoassays failed to deliver results, flagged with “signal level below limit”. Biotin therapy was ruled out as a possible interferent. In the first episode, re-assay of a repeat draw yielded same outcome; outsourcing on Immulite provided concentration of >738 pmol/l. Serial dilution gave result of >29520 pmol/l on Elecsys 2010. In the second, we gained from past experience. Vitamin B₁₂ concentration >59040 pmol/l was conveyed to the treating nephrologist the very day. The B₁₂ immunoassay on the Elecsys 2010 employs sequential incubation steps for competitive binding that is compromised in the event of abnormally excess B₁₂ concentration in patient sera akin to the prozone effect. This knowledge may be beneficial while assaying sera of CKD patients to avoid financial loss due unnecessary repeats and delay in turnaround time.     

Access免疫分析系统对运动员血清睾酮的快速检测

目的 :寻找一种快速、准确、灵敏、环保检测运动员血清睾酮的方法。方法 :应用Access全自动微粒子化学发光免疫分析系统 (Access免疫分析系统 )及配套试剂测定运动员血清睾酮(Testosterone ,T) ,并与放射免疫分析 (RIA)方法比较。结果 :Access免疫分析系统性能良好 ;重复性 :批内平均CV %=2 .3 5 ,批间平均CV %=4.0 4;基本无交叉污染。与RIA方法比较 ,睾酮r=0 .990 2 (P <0 .0 0 1)。结论 :Access免疫分析系统具有快速、准确、灵敏、测定范围宽 ,且无污染 ,能够及时为运动员训练监控提供依据。     

重金属汞离子免疫分析方法的研究

快速定量检出环境及食品中的重金属离子已成为世界范围内的研究热点。免疫分析方法具有灵敏度高、特异性强、速度快、成本低、容易操作等优点,被广泛应用到环境和食品中重金属离子的检测中。本文主要介绍了重金属汞离子抗原制备过程中双功能试剂的选择、单克隆抗体的制备以及免疫分析方法的建立,并且就其与新型分析方法的结合趋势进行了探讨。     

Performance evaluation of the high sensitive troponin I assay on the Atellica IM analyser

IntroductionThe Fourth Universal Definition of Myocardial Infarction Global Taskforce recommends the use of high sensitive troponin (hs-Tn) assays in the diagnosis of acute myocardial infarction. We evaluated the analytical performance of the Atellica IM High-sensitivity Troponin I Assay (hs-TnI) (Siemens Healthcare Diagnostics Inc., Tarrytown, USA) and compared its performance to other hs-TnI assays (Siemens Advia Centaur, Dimension Vista, Dimension EXL, and Abbott Architect (Wiesbaden, Germany)) at one or more sites across Europe.Materials and methodsPrecision, detection limit, linearity, method comparison, and interference studies were performed according to Clinical and Laboratory Standards Institute protocols. Values in 40 healthy individuals were compared to the manufacturer’s cut-offs. Sample turnaround time (TAT) was examined.ResultsImprecision repeatability CVs were 1.1–4.7% and within-lab imprecision were 1.8–7.6% (10.0–25,000 ng/L). The limit of blank (LoB), detection (LoD), and quantitation (LoQ) aligned with the manufacturer’s values of 0.5 ng/L, 1.6 ng/L, and 2.5 ng/L, respectively. Passing-Bablok regression demonstrated good correlations between Atellica IM analyser with other systems; some minor deviations were observed. All results in healthy volunteers fell below the 99th percentile URL, and greater than 50% of each sex demonstrated values above the LoD. No interference was observed for biotin (≤ 1500 µg/L), but a slight bias at 5.0 g/L haemoglobin and 50 ng/L Tn was observed. TAT from was fast (mean time = 10.9 minutes) and reproducible (6%CV).ConclusionsReal-world analytical and TAT performance of the hs-TnI assay on the Atellica IM analyser make this assay fit for routine use in clinical laboratories.     

Development of an electrochemical immunoassay for detection of gatifloxacin in swine urine

To detect gatifloxacin (GAT) residue in swine urine, an electrochemical immunoassay was established. An indirect competitive immunoassay was developed, in which the coating antigen is immobilized in an enzyme-linked immunosorbent assay (ELISA) plate and GAT residue from the sample competes with the limited binding sites in added anti-GAT antibody. Horseradish peroxidase (HRP) conjugated to goat anti-rabbit IgG was used as the enzymatic label. A carbon fiber working electrode was constructed and current signals were detected by using hydrogen peroxide as a substrate and hydroquinone as an electrochemical mediator. The electrochemical immunoassay was evaluated by analysis of GAT in buffer or swine urine and an average value of half inhibition concentration (IC₅₀) of 8.9 ng/ml was obtained. Excellent specificity of the antibody was achieved with little cross-reaction with lomefloxacin (3.0%), ciprofloxacin (3.0%), and ofloxacin (1.9%) among commonly used (fluoro)quinolones. In conclusion, the immunoassay system developed in this research can be used as a rapid, powerful and on-site analytical tool to detect GAT residue in foods and food products.     

化学发光法与放免法测定运动员血清睾酮的比较

研究目的：探讨化学发光免疫分析与放射免疫分析测定运动员血清睾酮的差异。研究方法：采用化学发光免疫分析与放射免疫分析方法同时测定同一批运动员血清睾酮(T)的浓度。研究结果：化学发光免疫分析和放射免疫分析两种方法测定男女运动员的血清T的结果无显著性差异(P＞0．05),两种方法测定结果具高度相关(P＜0．01)。结论：化学发光免疫分析和放射免疫分析两种方法测定运动员血清睾酮的浓度同样准确、可信,可相互参考,但化学发光免疫分析更具有快速、准确、灵敏、无污染等优点,使用化学发光免疫分析在运动医学领域将具有更加广阔的应用前景。     

纳米金增强伏安免疫分析

建立了一种新的纳米金增强伏安免疫分析方法.以人免疫球蛋白G（HIgG）为模型,羊抗人免疫球蛋白G（GAH IgG）固定于电极表面构成免疫传感器界面.固定化抗体与分析目标物HIgG发生免疫反应而将HIgG捕获,再通过夹心法将纳米金标记的GAH IgG结合于电极界面.通过金增强过程可在纳米金上进一步沉积金形成直径较大的纳米金颗粒,使电极表观面积大大增加,进而显著改善电极表面的电极表面吸附电化学行为,故用循环伏安法或差示脉冲法测定的金增强前后吸附伏安电流变化值可实现界面结合的金纳米探针的含量,从而间接实现分析目标物HIgG的测定.其线性范围为50 ng/mL~1μg/mL,检测限为20 ng/mL.实验表明该法灵敏度高,选择性好,实现简便,可望成为一种新型有潜力的高灵敏免疫传感技术.     

Determination of theophylline concentration in serum by chemiluminescent immunoassay

INTRODUCTION Theophylline is one of the antiasthmatic drugs commonly used in a clinic.The individual difference of its bio-availability and the elimination rate in vivo is very large(Vergin et al.,2003).Its valid blood drug level is10~20mg/L,and it has a narrow safety range(Dawson and Whyte,1999;Li et al.,2000).As it is apt to result in the serious side-effect if the blood drug level exceeds20mg/L,monitoring the blood drug level of theophylline is necessary.In many different methods fo…     

Current status of the lateral flow immunoassay for the detection of SARS-CoV-2 in nasopharyngeal swabs

Early detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and diagnosis of coronavirus disease 2019 (COVID-19) are priorities during the pandemic. Symptomatic and suspected asymptomatic individuals should be tested for COVID-19 to confirm infection and to be excluded from social interactions. As molecular testing capacity is overloaded during the pandemic, rapid antigen tests, such as lateral flow immunoassays (LFIAs), can be a useful tool as they allow greater test availability and obtain results in a very short time. This short review aims to present the analytical properties of LFIAs in the detection of SARS-CoV-2 in nasopharyngeal swabs. Lateral flow immunoassay is a method that combines thin-layer chromatography and indirect immunochemical sandwich method and allows the detection of a specific SARS-CoV-2 antigen in nasopharyngeal swabs. Swab specimens should be adequately collected and tested as soon as possible. Users should pay attention to quality control and possible interferences. Antigen tests for SARS-CoV-2 show high sensitivity and specificity in cases with high viral loads, and should be used up to five days after the onset of the first symptoms of COVID-19. False positive results may be obtained when screening large populations with a low prevalence of COVID-19 infection, while false negative results may happen due to improper specimen collection or insufficient amount of antigen in the specimen. So as to achieve reliable results, a diagnostic accuracy study of a specific rapid antigen test should be performed.     

Biological variation of plasma ferritin in healthy adult males in south Indian population—A sample study

A sample study of biological variation of plasma ferritin in healthy adult males 19–25 years of age (n=6) in the Indian population was determined. Venous blood was collected on 3 non-consecutive days during a 3 week period. Plasma ferritin was measured using enzyme linked immunoassay in an automated immunoassay system. Analytical and Biological variation was calculated. We found a mean biological variation of 21.64%. Thus, our results indicate that biological variation contributed most to the intraindividual variation.