Comparison of four digoxin immunoassays with respect to interference from digoxin-like immunoreactive factors

Objectives: Comparison of a new monoclonal digoxin assay with three polyclonal digoxin assays for their cross-reactivity to digoxinlike immunoreactive factors (DLIF) and digoxin metabolites.

Design and Methods: Sixty-:six nondigitalized patient samples from 5 different groups: neonates, women in 3rd trimester pregnancy, and patients with liver or renal diseases, or undergoing organ transplants, and 139 samples from digoxin-treated patients of 4 categories (hospital sick, liver, renal, and outpatients) were compared in 4 different digoxin assays: (a) ACS™ Digoxin (ACS) developed for the automated chemiluminescent Ciba Corning ACS 180^® system, (b) Baxter Stratus™ (Stratus, a fluoroimmunoassay), (c) Ciba-Corning Magic^TM (Magic, a radioimmunoassay), and (d) an in-house radioimmunoassay (RIA). The ACS^TM and RIA were also compared for their cross-reactivity to four principal digoxin metabolites.

Results and Conclusion: Among the nondigitalized specimens, no significant DLIF interference was found for all 4 assays among the pregnant women or liver and transplant patients. However, the neonates registered high DLIF interference with Magic™ and RIA, but none for ACS™ or Stratus™. DLIF interference in renal samples was highest in the Magic assay and lowest in RIA. Among the specimens with digoxin, a higher number of discrepant samples were found from the sick patients than from outpatients. In 75% of such discrepant samples, the ACS™ result was less than other assay results, suggesting DLIF as the probable cause. The two assays differed most in their cross-reactivity to the deglycated metabolites, digoxigenin and its mono-digitoxoside.     

Rapid detection of oleander poisoning by Dimension Vista digoxin assay (Flex Reagent Cartridge)

Oleander poisoning can be detected by digoxin immunoassays and for last two decades the fluorescence polarization immunoassay (FPIA) has been used for rapid detection of oleander poisoning in clinical laboratories. Recently, Abbott Laboratories (Abbott Park, IL) discontinued this assay. Therefore, we explored the possibility of using another digoxin assay (Dimension Vista Flex Reagent Cartridge, Tina Quant, EMIT 2000 and old FPIA assay for comparison) for rapid detection of oleander poisoning. When aliquots of drug-free serum pools were supplemented with pure oleandrin or oleander extract, we observed the highest apparent digoxin values using Dimension Vista digoxin assay (Flex Reagent Cartridge). We also observed significant apparent digoxin values in vivo in sera of mice both 1 and 2 hr after feeding with oleander extract. When a serum pool prepared from patients taking digoxin was further supplemented with various amounts of oleander extract, the highest falsely elevated digoxin values were observed with Dimension Vista digoxin assay. Monitoring free digoxin using Dimension Vista digoxin assay (Flex Reagent Cartridge) did not eliminate this interference. Digibind neutralized digoxin-like factors of oleander extract and such effect can be monitored by observing significant reduction in apparent free digoxin levels in the presence of Digibind as measured in the protein-free ultrafiltrate using Dimension Vista digoxin assay (Flex Reagent Cartridge).     

Current status of fluorescent immunoassays

In 1941 fluorescent compounds were first introduced as immunochemical labels in assay systems. Several forms of quantitative fluorescent immunoassay, which represent a major alternative to radioimmunoassay and enzyme immunoassay, have been developed and are now widely used in many clinical laboratories. This paper discusses these forms and procedures and their advantages over radioimmunoassay and enzyme immunoassay.     

血液灌流对地高辛中毒患者治疗作用的临床研究

目的研究血液灌流对地高辛中毒患者的治疗作用。方法严重地高辛中毒患者6例,给予血液灌流治疗,观察血液灌流对血中地高辛浓度和中毒症状的影响。结果经过一次或两次血液灌流治疗可消除地高辛的中毒症状,非常显著地降低血中地高辛的浓度。结论血液灌流能有效地清除血中的地高辛。     

地高辛中毒24例原因分析

目的分析导致地高辛中毒的相关原因。方法 24例接受地高辛治疗的心力衰竭患者,风湿性心脏病并心力衰竭2例,冠心病并心力衰竭8例,高血压性心脏病并心力衰竭4例,扩张型心肌病并心力衰竭1例,肺源性心脏病并心力衰竭9例,对导致地高辛中毒的因素进行分析。结果地高辛中毒与肝肾功能、电解质紊乱、年龄、缺氧、相关药物等有关2,4例病例均全部早期发现,早期治疗。结论使用地高辛时对易导致中毒的高危人群应及时监测血药浓度,调整剂量。     

Laboratory diagnosis of syphilis with automated immunoassays

The serological detection of specific antibodies to Treponema pallidum is of particular importance in the diagnosis of syphilis. The purpose of this study was to evaluate diagnostic performances of automated immunoassays in comparison with T. pallidum hemagglutination test (TPHA) and Western Blot (WB). The retrospective study was performed with different panels of sera: 244 clinical and serological characterized syphilitic sera and 203 potentially interfering samples. All the sera were tested by Enzygnost Syphilis, ARCHITECT Syphilis TP, TPHA, and homemade WB. The diagnostic performances of the two assays were very similar: both Enzygnost Syphilis and ARCHITECT Syphilis TP performed with a sensitivity of 99.2%, whereas the specificity was 98.5 and 98.4%, respectively. Considering the suitability for automation, both immunoassays may represent a good choice as a screening test. However, the use of a confirmatory test, such as TPHA or WB, remains a must in order to avoid false‐positive results. J. Clin. Lab. Anal. 23:1–6, 2009. © 2009 Wiley‐Liss, Inc.     

CEDIA法测定血清地高辛的实验观察与临床应用

目的克隆酶供体免疫分析技术（CEDIA）与放免法（RIA）测定血清地高辛的两种实验方法的观察比较。方法采用CEDIA对206例心脏疾病患者的血清地高辛浓度进行测定。结果经统计学分析，151例非中毒组和55例中毒组血清地高辛浓度分别为1．23±0．46ng／ml和2．59±0．62ng／ml。结论实验结果与国外报道接近，与放射免疫分析进行相关实验，结果r=0．9263，相关良好。     

Fatal digoxin poisoning: An unsuccessful resuscitation with use of digoxin-immune Fab

A 1-month-old infant suffered cardiac arrest shortly after presentation to the emergency department. The child had a history of heart disease treated with digoxin. The infant died despite intensive resuscitative efforts, including the use of digoxin-specific Fab antibodies. A brief discussion of this case and the use of digoxin-specific antibodies is presented.     

Evaluation of the performance of 5 commercialized enzyme immunoassays for the detection of Taenia solium antibodies and for the diagnosis of neurocysticercosis

This study aimed to evaluate 5 enzyme immunoassays for detecting human antibodies against Taenia solium in human serum and for the diagnosis of neurocysticercosis (NCC): DRG™, RIDASCREEN™, NOVATECH™, CYPRESS™, and IVD™. A collection of 114 reference serum samples were used. All sera were tested both by ELISA and by an immunoblot method (enzyme-linked immunoelectrotransfer blot [EITB]). When compared with EITB, the Ridascreen™ test had the best positive concordance rate (85.1-91.2%) and the NovaLisa test™ showed the optimal negative concordance rate (93.7-95.6%). All tests had a sensitivity under 72% and a specificity above 60%. The best sensitivity was obtained using Ridascreen™ test (71.4%). An optimal specificity was achieved by the NovaLisa test™. T. solium-positive sera all cross-reacted with E. granulosus positive samples. In the commercial assays evaluated here, the most appropriate ELISA test for screening may be the Ridascreen™ assay. Antibody detection seems to be not appropriate for NCC diagnosis because of its overall lack of sensitivity.     

Performance characteristics of five automated serum cortisol immunoassays

BACKGROUND: Serum cortisol measurements are used to help diagnose conditions of cortisol deficiency and excess. Automated, nonisotopic immunoassays are used in most clinical laboratories. METHODS: Linearity, imprecision, and method comparison studies for serum cortisol assays were performed with the Access, Advia Centaur, AxSYM, Elecsys 2010, and IMMULITE 2000 analyzers. RESULTS: All methods demonstrated acceptable linearity with the AxSYM method showing the least deviation from target values. The Elecsys 2010 method was the most precise for all three levels of quality control material. Method comparison studies demonstrated good concordance among methods except for two patient samples that gave results on the Elecsys 2010 that were significantly higher than the other methods. Differences in assay calibration were observed. CONCLUSIONS: Overall, all methods performed well. Additional calibration standardization efforts are required to truly harmonize the results from each assay. The Elecsys 2010 method is less specific than other automated methods based on two discordant patient results.     

Clinical outcomes from early use of digoxin-specific antibodies versus observation in chronic digoxin poisoning (ATOM-4)

Introduction: In our previous study on chronic digoxin poisoning, there was a minor improvement after treatment with digoxin-specific antibody (digoxin-Fab). We hypothesised patients with elevated digoxin concentrations may derive little benefit from digoxin-Fab because their presenting complaint was more closely related to their multiple co-morbidities. We aimed to compare the outcome of patients who were initially treated with digoxin-Fab with those that received supportive care.

Method: Patients were prospectively recruited to the study if they had an elevated digoxin concentration, signs or symptoms of toxicity thought to be from digoxin. Patients who were initially managed with digoxin-Fab were compared with those not initially receiving digoxin-Fab (observation group). Patients presented with ventricular arrhythmias before initial assessment were excluded from the analysis. Primary outcome was mortality. Secondary outcomes were length of stay (LOS), change in heart rate (HR) and potassium concentration.

Results: From September 2013 to January 2018, 128 patients were recruited of which 78 (61%) received initial digoxin-Fab. Digoxin-Fab and supportive care groups had an initial median heart rate of 46 (range: 20–120) vs 52 bpm (range: 29–91) (p?=?.06), systolic blood pressure of 110?mmHg (range: 65–180) vs 125?mmHg (range: 90–184) (p?=?.009), respectively. Digoxin concentrations 4.4?nmol/L (range: 3.3–9) vs 4.2 (range: 2–11.2) (p?=?.42) and potassium concentrations 5.4?mmol/L (range: 3–11) vs 5.1?mmol/L (range: 3.5–8.2) (p?=?.33) were similar. Median dose of digoxin-Fab used was 1.5 vials (IQR: 1–2). There were 9 (12%) deaths in the Fab group compared to 7 (14%) in those treated with supportive care (risk difference ?2.5%; 95% CI: ?14 to 9%; p?=?.68). The median LOS was six days in both groups. Mean changes in potassium concentration [?0.5?±?0.1 vs. ?0.4?±?0.1?mmol/L; difference ?0.1 (95% CI: ?.02, 0.4), p?=?.70] and HR within 4?h [8?±?1 vs. 7?±?3 bpm; difference ?1.0 (95% CI: ?6.7, 4.8), p?=?0.74] were similar in the two groups.

Conclusions: This study did not appear to show any benefit from the routine use of digoxin-Fab in patients thought to have chronic digoxin poisoning. These patients have multiple co-morbidities that may be contributing to their clinical features, other treatments are often equally effective.     

Rapid speciation of the five most medically relevant candida species using PCR amplification and a microtiter plate-based detection system

Background: Diagnosis of disseminated candidiasis can be difficult, as patient symptoms are often vague and blood cultures negative despite systemic involvement. Rapid detection of Candida would be advantageous, as delays in initiating antifungal therapy increase mortality. Conventional blood culturing methods require at least 3-7 days for detecting and speciating isolates, especially non-albicans species. In contrast, DNA amplification techniques make it possible to detect Candida DNA directly from clinical samples, thus eliminating the need to culture.Methods and Results: This study describes a polymerase chain reaction (PCR)-based assay, which permits amplification and speciation of the five most medically relevant Candida species, which cause over 95% of all Candida infections, namely, C. albicans, C. tropicalis, C. (Torulopsis) glabrata, C. parapsilosis, and C. krusei. Speciating these isolates has become more important recently with the introduction of fluconazole, and antifungal drug that has lower nephrotoxicity than fungizone but a narrower host range.Conclusions: By using this PCR-based assay in conjunction with a rapid microtiter plate-based detection system, samples can be analyzed for Candida DNA from five species in a single day. This represents a significant time saving as compared with the more lengthy but commonly used techniques of agarose gel electrophoresis and Southern blot hybridization for PCR product detection. (Mol Diagn 1996 Jun;1(1):51-58)     

Effect of Asian ginseng, Siberian ginseng, and Indian ayurvedic medicine Ashwagandha on serum digoxin measurement by Digoxin III, a new digoxin immunoassay

Asian ginseng, Siberian ginseng, and Indian Ayurvedic medicine Ashwagandha demonstrated modest interference with serum digoxin measurements by the fluorescent polarization immunoassay (FPIA). Recently, Abbott Laboratories marketed a new digoxin immunoassay, Digoxin III for application on the AxSYM analyzer. We studied potential interference of these herbal supplements on serum digoxin measurement by Digoxin III assay in vitro and compared our results with the values obtained by Tina-quant assay. Aliquots of drug-free serum pool were supplemented with various amounts of Asian ginseng, Siberian ginseng, or Ashwagandha approximating expected concentrations after recommended doses and overdoses of these herbal supplements in serum. Then digoxin concentrations were measured by the Digoxin III and Tina-quant (Roche Diagnostics) assay. We also supplemented aliquots of a digoxin pool prepared from patients receiving digoxin with various amounts of these herbal supplements and then measured digoxin concentrations again using both digoxin immunoassays. We observed modest apparent digoxin concentrations when aliquots of drug-free serum pool were supplemented with all three herbal supplements using Digoxin III assay (apparent digoxin in the range of 0.31-0.57 ng/ml), but no apparent digoxin concentration (except with the highest concentration of Ashwagandha supplement for both brands) was observed using the Tina-quant assay. When aliquots of digoxin pool were further supplemented with these herbal supplements, digoxin concentrations were falsely elevated when measured by the new Digoxin III assay. For example, we observed 48.2% (1.63 ng/ml digoxin) increase in digoxin concentration when an aliquot of Digoxin pool 1 (1.10 ng/ml digoxin) was supplemented with 50 microl of Asian ginseng extract (Brand 2). Measuring free digoxin does not eliminate the modest interferences of these herbal supplements in serum digoxin measurement by the Digoxin III assay.     

The effects of digoxin and β-methyldigoxin on the heart rate of decompensated patients with atrial fibrillation

Eighteen patients with atrial fibrillation were given digoxin 0.13 mg twice daily for 3 weeks and beta-methyldigoxin 0.10 mg twice daily for another 3 weeks. At the end of each 3 week period an exercise test was performed and the effects on the heart rate of the two drugs were compared. No difference in heart rate was obtained at rest, whereas the heart rate after 6 min of exercise was higher during treatment with digoxin (131 beats/min) than when the patients were taking beta-methyldigoxin (124 beats/min). There were no significant differences between digoxin and beta-methyldigoxin in their effects on the ECG (R-R intervals, T-wave, Q-T duration). The plasma concentrations of the two glycosides were determined by radioimmunoassay and by 86Rb-uptake inhibition assay. Comparable plasma concentration values (1.0 ng/ml for digoxin, 1.1 ng/ml for beta-methyldigoxin, mean values) were obtained by radioimmunoassay, but the 86Rb-technique gave significantly higher values (mean 1.5 ng/ml) for beta-methyldigoxin. It is concluded that beta-methyldigoxin is equal to digoxin for producing slowing of the heart rate in patients with atrial fibrillation.     

应用基因芯片快速检测临床常见细菌

目的 应用基因芯片对临床常见的8种致病细菌进行检测.方法 选取8种临床常见的致病细菌,包括金黄色葡萄球菌、铜绿假单胞菌、肺炎克雷伯菌、大肠杆菌、奇异变形杆菌、产气肠杆菌、荧光假单胞菌、宋内志贺菌.以16S rRNA基因为目的基因,白行设计通用引物系列扩增目的片段,针对高变区域设计探针,建立基因芯片检测体系,并对所选细菌...     

TaqMan实时荧光定量PCR检测肺炎链球菌

目的利用实时荧光定量聚合酶链反应（实时PCR）方法进行肺炎链球茵的检测和流行病学调查。方法用实时PCR技术扩增并检测400例临床标本的肺炎链球菌的自溶素（1yt）基因,并将其与传统的培养法进行对比。结果400例,临床标本中,实时PCR检测肺炎链球菌为阳性的有78例（阳性率为18％）,传统培养法结果为阳性的有29例（阳性率为7．25％）。结论实时PCR是一种灵敏、特异、快速的检测肺炎链球菌方法,其可用于肺炎链球菌的诊断和流行病学调查。     

A comparison of SARS-CoV-2 nucleocapsid and spike antibody detection using three commercially available automated immunoassays

IntroductionCommercially available serological assays for SARS-CoV-2 detect antibodies to either the nucleocapsid or spike protein. Here we compare the performance of the Beckman-Coulter SARS-CoV-2 spike IgG assay to that of the Abbott SARS-CoV-2 nucleocapsid IgG and Roche Anti-SARS-CoV-2 nucleocapsid total antibody assays. In addition, we document the trend in nucleocapsid and spike antibodies in sequential samples collected from convalescent plasma donors.MethodsPlasma or serum samples from 20 individual SARS-CoV-2 RT-PCR-positive inpatients (n = 172), 20 individual convalescent donors with a previous RT-PCR-confirmed SARS-CoV-2 infection (n = 20), were deemed positive SARS-CoV-2 samples. RT-PCR-negative inpatients (n = 24), and 109 pre-SARS-CoV-2 samples were determined to be SARS-CoV-2 negative. Samples were assayed by the Abbott, Roche, and Beckman assays.ResultsAll three assays demonstrated 100% specificity. Abbott, Beckman, and Roche platforms had sensitivities of 98%, 93%, and 90% respectively, with the difference in sensitivity attributed primarily to samples from immunocompromised patients. After the exclusion of samples immunocompromised patients, all assays exhibited ≥ 95% sensitivity. In sequential samples collected from the same individuals, the Roche nucleocapsid antibody assay demonstrated continually increasing signal intensity, with maximal values observed at the last time point examined. In contrast, the Beckman spike IgG antibody signal peaked between 14 and 28 days post positive SARS-CoV-2 PCR and steadily declined in subsequent samples. Subsequent collections 51–200 days (median of 139 days) post positive SARS-CoV-2 RT-PCR from five inpatients and five convalescent donors revealed that spike and nucleocapsid antibodies remained detectable for several months after confirmed infection.ConclusionsThe three assays are sensitive and specific for SARS-CoV-2 antibodies. Nucleocapsid and spike antibodies were detectable for up to 200 days post-positive SARS-CoV-2 PCR but demonstrated markedly different trends in signal intensity.     

Rapid and specific detection of PCR products using light-up probes

Newly developed light-up probes offer an attractive tool for PCR product detection. The light-up probe, which consists of a thiazole orange derivative linked to a peptide nucleic acid oligomer, hybridizes specifically to complementary nucleic acids. Upon hybridization the thiazole orange moiety interacts with the nucleic acid bases and the probe becomes brightly fluorescent. This eliminates the need to separate bound from unbound probes and reduces the risk of cross contamination during sample handling. We demonstrate here the applicability of light-up probes in two different PCR assays, one directed towards the human beta-actin gene and the other towards the invA gene of Salmonella. The probes do not interfere with the PCR reaction and can either be included in the sample mixture or added after completed amplification. The specificity of the probe is found to be excellent: a single-base mismatch in the target sequence is sufficient to prevent probe binding as indicated by the lack of fluorescence increase. Furthermore, a clear correlation is found between the intensity of gel bands and the measured probe fluorescence in solution, which suggests that the amount of PCR products can be quantified using light-up probes.