Elecsys Assay Research Articles

Serum human epididymis protein 4 (HE4) may be a better tumor marker in early lung cancer

BackgroundHuman epididymis protein 4 (HE4) had been shown to be an ideal biomarker in ovarian cancer. However, there were fewer reports on its application in lung cancer. We explored the diagnostic value of serum HE4 as a biomarker in early lung cancer by comparing it with other biomarkers. Methods162 individuals including 112 cases of lung cancer at early stage and 50 healthy people as controls were enrolled. The serum concentrations of biomarkers were determined with the Roche Elecsys assays. ResultsIn comparison to the other biomarkers such as carcinoembryonic antigen (CEA), neuron-specific-enolase (NSE), serum cytokeratin 19 fragment (CYFRA 21-1) and progastrinreleasing peptide (proGRP), serum HE4 was one of the biomarkers with the highest sensitivity (43.8%) and specificity (95.0%) for early lung cancer diagnosis. In terms of histological results, serum HE4 was the best biomarker both in adenocarcinoma (AC) and squamous carcinoma (SC), and serum proGRP was the best in small cell lung cancer (SCLC). The combination of proGRP, NSE and HE4 could determine the histological type of lung cancer with a very high accuracy of 93.8%. ConclusionsThese findings suggested that serum HE4 was a better biomarker in early lung cancer than other frequently-used biomarkers.

Performance Evaluation of the Elecsys Neuron-Specific Enolase Assay

This article is available from http://www.labmedonline.org 2015, Laboratory Medicine Online This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Neuron-specific enolase (NSE) is an enzyme specifically found in neurons and neuroendocrine tissue. It is a common marker for small cell lung cancer diagnosis and is also useful as a predictor of brain damage. This study evaluates the performance of Elecsys NSE (Roche Diagnostics, Switzerland), an electrochemiluminescent immunoassay. Methods: The precision, linearity, limit of detection, and reference interval of the Elecsys NSE, as well as the correlation between Elecsys NSE and ELSA-NSE (Cis-Bio International, France) were evaluated in accordance with the Clinical Laboratory Standards Institute (CLSI) guidelines. PreciControl Tumor Marker (Roche Diagnostics), patient sera, and sera from healthy individuals were used for the analysis. Results: The measured coefficient of variation for the assay was below 3%, and it demonstrated linearity from 0.20 to 234.5 ng/mL. The detection limit was 0.032 ng/mL and the reference interval ranged from 0.05 to 16.3 ng/mL. Compared with the ELSA-NSE assay, the correlation coefficient was 0.9128. Conclusions: The Elecsys assay showed suitable precision, linearity, limit of detection and reference range for clinical laboratory use; however, the correlation coefficient of Elecsys NSE as compared to ELSA-NSE was below 0.975. This result may be associated with the use of different monoclonal antibodies in the two different NSE assays. Elecsys NSE demonstrated a high sensitivity without the use of radioactive reagents; therefore, Elecsys NSE will be quite useful for NSE analysis in the clinical laboratory setting.

Clinical performance of a new hepatitis B surface antigen quantitative assay with automatic dilution

Hepatitis B virus surface antigen (HBsAg) levels reflect disease status and can predict the clinical response to antiviral treatment; however, the emergence of HBsAg mutant strains has become a challenge. The Abbott HBsAg quantification assay provides enhanced detection of HBsAg and HBsAg mutants. We aimed to evaluate the performance of the Abbott HBsAg quantification assay with automatic sample dilutions (shortened as automatic Architect assay), compared with the Abbott HBsAg quantification assay with manual sample dilutions (shortened as manual Architect assay) and the Roche HBsAg quantification assay with automatic sample dilutions (shortened as Elecsys). A total of 130 sera samples obtained from 87 hepatitis B virus (HBV)-infected patients were collected to assess the correlation between the automatic and manual Architect assays. Among the 87 patients, 41 provided 42 sera samples to confirm the linearity and reproducibility of the automatic Architect assay, and find out the correlation among the Elecsys and two Architect assays. The coefficients of variation (0.44–9.53%) and R2 = 0.996–1, which were both determined using values obtained from the automatic Architect assay, showed good reproducibility and linearity. Results of the two Architect assays demonstrated a feasible correlation (n = 130 samples; R = 0.898, p < 0.01). With regard to subgroups, correlations between the two Architect assays were better in the hepatitis B e antigen (HBeAg)-negative group (HBeAg-negative group vs. HBeAg-positive group: R = 0.885 vs. R = 0.865, both p < 0.01) and low HBV DNA group (low DNA group vs. high DNA group: R = 0.886 vs. R = 0.844, both p < 0.01). Significant correlations were also found between the results of the Elecsys and Architect assays (R > 0.93 in all cases). In conclusion, the correlation between the automatic and manual dilution Architect assays was feasible, particularly in the HBeAg-negative and low DNA groups. With lower labor costs and less human error than the manual version, the Abbott automatic dilution Architect assay provided a good clinical performance with regard to the HBsAg levels.

Diagnosis of preeclampsia with soluble Fms–like tyrosine kinase 1/placental growth factor ratio: an inter–assay comparison

The angiogenic factor ratio soluble Fms–kinase 1 (sFlt–1)/placental growth factor (PlGF) is a novel diagnostic tool for preeclampsia. We compared the efficacy of the KRYPTOR (BRAHMS) automated assays for sFlt–1 and PlGF with the Elecsys (Roche) assays in a routine clinical setting. Preeclamptic women (n = 39) were included shortly after the time of diagnosis. Normotensive control pregnancies were matched by gestational age (n = 76). The KRYPTOR assays performed comparably or superior to Elecsys (sFlt–1/PlGF area under the curve 0.746 versus 0.735; P = .09; for non–obese 0.820 versus 0.805, P = .047). For early–onset preeclampsia, KRYPTOR area under the curve increased to 0.929 with a 100% specificity for preeclampsia at cut–off 85 and an 88.9% sensitivity for preeclampsia at cut–off 33. For women with preeclampsia and preterm delivery or Hemolysis, Elevated Liver enzymes, Low Platelet count (HELLP) syndrome, the KRYPTOR sFlt–1/PlGF ratio was manifold increased (P < .01). The sFlt–1/PlGF ratio proved especially useful in early–onset preeclampsia, preeclampsia with preterm delivery or HELLP, and among non–obese women.

Regional adjustment of thyroid hormone reference intervals

Abstract Background: We conducted a study in a metropolitan area to establish regional reference intervals for thyreotropin (TSH) and the thyroid hormones free triiodthyronine (fT3) and free thyroxine (fT4). This was due to the different reference ranges, based on varying regional trials, presented for a widely used electrochemiluminescence immunoassay system. Methods: We investigated 292 apparently healthy adult subjects and excluded those with known history of thyroid disease, abnormal findings in the ultrasonographic examination of the thyroid gland, or elevated thyroid autoantibodies in serum. Accordingly, 204 of 292 subjects were included as the reference collective. We measured serum concentrations of TSH, fT3, and fT4 using the Elecsys assays from Roche Diagnostics and calculated the 2.5th and 97.5th percentiles. Results: The nonparametrically calculated reference values for TSH and fT4 were 0.58–3.49 mIU/L and 11.58–20.46 pmol/L, respectively. Statistically remarkable is the finding of a normal Gaussian distribution of the fT3 serum concentration, leading to the parametric reference interval of 3.56–5.88 pmol/L. Conclusions: The established reference values for this regional collective showed tighter intervals than the reference ranges provided by the manufacturer. A carefully selected study population, based on the correspondent National Academy of Clinical Biochemistry criteria, ensured a valid set of reference ranges for TSH, fT3, and fT4, providing a basis for accurate in vitro thyroid testing. The 2.5th percentile for the fT3 is now in better accordance with clinical findings.

Cross-reactivity of steroid hormone immunoassays: clinical significance and two-dimensional molecular similarity prediction.

BackgroundImmunoassays are widely used in clinical laboratories for measurement of plasma/serum concentrations of steroid hormones such as cortisol and testosterone. Immunoassays can be performed on a variety of standard clinical chemistry analyzers, thus allowing even small clinical laboratories to do analysis on-site. One limitation of steroid hormone immunoassays is interference caused by compounds with structural similarity to the target steroid of the assay. Interfering molecules include structurally related endogenous compounds and their metabolites as well as drugs such as anabolic steroids and synthetic glucocorticoids.MethodsCross-reactivity of a structurally diverse set of compounds were determined for the Roche Diagnostics Elecsys assays for cortisol, dehydroepiandrosterone (DHEA) sulfate, estradiol, progesterone, and testosterone. These data were compared and contrasted to package insert data and published cross-reactivity studies for other marketed steroid hormone immunoassays. Cross-reactivity was computationally predicted using the technique of two-dimensional molecular similarity.ResultsThe Roche Elecsys Cortisol and Testosterone II assays showed a wider range of cross-reactivity than the DHEA sulfate, Estradiol II, and Progesterone II assays. 6-Methylprednisolone and prednisolone showed high cross-reactivity for the cortisol assay, with high likelihood of clinically significant effect for patients administered these drugs. In addition, 21-deoxycortisol likely produces clinically relevant cross-reactivity for cortisol in patients with 21-hydroxylase deficiency, while 11-deoxycortisol may produce clinically relevant cross-reactivity in 11β-hydroxylase deficiency or following metyrapone challenge. Several anabolic steroids may produce clinically significant false positives on the testosterone assay, although interpretation is limited by sparse pharmacokinetic data for some of these drugs. Norethindrone therapy may impact immunoassay measurement of testosterone in women. Using two-dimensional similarity calculations, all compounds with high cross-reactivity also showed a high degree of similarity to the target molecule of the immunoassay.ConclusionsCompounds producing cross-reactivity in steroid hormone immunoassays generally have a high degree of structural similarity to the target hormone. Clinically significant interactions can occur with structurally similar drugs (e.g., prednisolone and cortisol immunoassays; methyltestosterone and testosterone immunoassays) or with endogenous compounds such as 21-deoxycortisol that can accumulate to very high concentrations in certain disease conditions. Simple similarity calculations can help triage compounds for future testing of assay cross-reactivity.

Erythrocyte binding preferences and receptor specificities of influenza virus

Background: Chronic hepatitis B infection (CHBI) is known to be associated with dysfunction of cellmediated immunity. However, little is known about the changes of immune response during CHBI, particularly the correlation between alterations of peripheral immune cell populations with hepatitis B surface antigen (HBsAg) levels and hepatitis B e antigen (HBeAg) status. Our goal is to look into the alteration of peripheral blood lymphocytes (PBL) including B lymphocytes, NK cells and T cells subsets in patients with (CHBI) and to elucidate their correlation with the level of HBsAg (qHBsAg) and HBeAg status. Methods & Materials: The immunophenotype profile of PBLs in 50 CHB patients and 20 age and sex matched healthy donors were analysed by flowcytometry (FCM). The profile of T cell subsets in patientswas also analysed based on the presence or absence of HBeAg and on the quantitation of HBsAg. Serum HBsAg was quantified by Elecsys assay (Roche Diagnostics, Germany). Results: Significant alteration in PBL percentage of the T lymphocytes subset were found in patients as compared to healthy controls showing reduction inbothCD4+andCD8+ cells (p <0.001) as well as reduction in CD4+ /CD8+ ratio (p <0.01). Meanwhile, there were no significant changes in other PBLs (Total T, B, and NK cells). There was no significant alteration in the percentage of T lymphocytes between HBeAg positive and HBeAg negative patients.However, an important correlationwasobservedbetween HBsAg level and the percentage of T andNK cells (r = 0.366; p<0.01, r = 0.462; p<0.01 respectively). Conclusion: Our findings suggest that there is evidence of alteration in the immunological response in chronic hepatitis B infection, reflected in the significant changes in the peripheral blood lymphocyte population subsets and serum HBsAg levels, which may affect the progression of the disease process in these patients.

Clinical evaluation of the Roche Elecsys® CMV IgG Avidity assay

Congenital cytomegalovirus (CMV) infection has potentially severe consequences in newborns. The testing of pregnant women for CMV-specific antibodies may be useful for the identification of women at risk of transmitting the infection to the fetus. The determination of CMV IgG avidity helps to establish the timing of infection as IgG avidity matures during the course of infection. This study examines the performance of the Elecsys® CMV IgG Avidity assay using preselected samples from patients at different phases of CMV infection. The Elecsys® CMV IgG Avidity assay was tested at three sites using sequential samples from patients with recent primary CMV infection, as well as single samples from patients with recent primary or past CMV infection. The Elecsys® assay discriminated well between early (low avidity) and late (high avidity) phases of infection in sequential serum samples. Overall, 98.8 % of low-avidity samples corresponded to infection onset <180 days before sampling and 77.8 % of all high-avidity results corresponded to infection onset >90 days before sampling. The assay’s sensitivity was 90–97 %, with specificity ranging from 89 to 100 %, depending on the consideration of gray-zone avidity values. Single samples from recent primary or past infection showed similar distributions of avidity results. The Elecsys® CMV IgG Avidity assay results are in agreement with preselected samples from patients with primary or past CMV infection, showing that the test is an adequate predictor of the phase of infection.

Screening models using multiple markers for early detection of late-onset preeclampsia in low-risk pregnancy

BackgroundOur primary objective was to establish a cutoff value for the soluble fms-like tyrosine kinase 1(sFlt-1)/placental growth factor (PlGF) ratio measured using the Elecsys assay to predict late-onset preeclampsia in low-risk pregnancies. Our secondary objective was to evaluate the ability of combination models using Elecsys data, second trimester uterine artery (UtA) Doppler ultrasonography measurements, and the serum fetoplacental protein levels used for Down’s syndrome screening, to predict preeclampsia.MethodsThis prospective cohort study included 262 pregnant women with a low risk of preeclampsia. Plasma levels of pregnancy-associated plasma protein-A (PAPP-A) and serum levels of alpha-fetoprotein, unconjugated estriol, human chorionic gonadotropin, and inhibin-A were measured, and sFlt-1/PlGF ratios were calculated. All women underwent UtA Doppler ultrasonography at 20 to 24 weeks of gestation.ResultsEight of the 262 women (3.0%) developed late-onset preeclampsia. Receiver operating characteristic curve analysis showed that the third trimester sFlt-1/PlGF ratio yielded the best detection rate (DR) for preeclampsia at a fixed false-positive rate (FPR) of 10%, followed by the second trimester sFlt-1/PlGF ratio, sFlt-1 level, and PlGF level. Binary logistic regression analysis was used to determine the five best combination models for early detection of late-onset preeclampsia. The combination of the PAPP-A level and the second trimester sFlt-1/PlGF ratio yielded a DR of 87.5% at a fixed FPR of 5%, the combination of second and third trimester sFlt-1/PlGF ratios yielded a DR of 87.5% at a fixed FPR of 10%, the combination of body mass index and the second trimester sFlt-1 level yielded a DR of 87.5% at a fixed FPR of 10%, the combination of the PAPP-A and inhibin-A levels yielded a DR of 50% at a fixed FPR of 10%, and the combination of the PAPP-A level and the third trimester sFlt-1/PlGF ratio yielded a DR of 62.5% at a fixed FPR of 10%.ConclusionsThe combination of the PAPP-A level and the second trimester sFlt-1/PlGF ratio, and the combination of the second trimester sFlt-1 level with body mass index, were better predictors of late-onset preeclampsia than any individual marker.

Screening models for early detection of late-onset preeclampsia with various markers in low-risk pregnancy population

Screening models for early detection of late-onset preeclampsia with various markers in low-risk pregnancy population

An immunoglobulin G complexed form of thyroid-stimulating hormone (macro thyroid-stimulating hormone) is a cause of elevated serum thyroid-stimulating hormone concentration

Macrocomplexes can be the cause of elevated serum hormone concentrations and may cause diagnostic confusion. This is well recognized for prolactin and commonly screened for using polyethylene glycol (PEG) precipitation. The phenomenon and a suitable screening method is less familiar with respect to thyroid-stimulating hormone (TSH). Samples sent to the laboratory for routine analysis of thyroid function and found to have a TSH >10 mU/L were evaluated to determine the prevalence of macro-TSH in the Roche Elecsys assay, using PEG precipitation with confirmation by gel filtration chromatography. Of 495 samples tested, 3 (0.6%) were found to have macro-TSH. From the distribution of recoveries, a cut-off <25% was determined for identifying samples requiring further investigation for the presence of macro-TSH. The prevalence of elevated TSH due to macro-TSH was found to be 0.6%. Laboratories should be aware of this cause of assay interference.

Quantification of hepatitis B surface antigen and E antigen: correlation between Elecsys and Architect assays

Quantification of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) and their change model during treatment are emerging as a useful tool for assessing the outcome of hepatitis B virus (HBV) infection and predicting the efficacy of antiviral therapy. The aim of this study was to compare the performance of the Elecsys and Architect assays for HBsAg and HBeAg quantification. Quantification of HBsAg and HBeAg, determined by these two assays, were assessed in 1292 sera from patients with chronic hepatitis B(CHB). HBeAg quantification in serum was performed by calibrating the results through HBeAg Paul-Ehrlich international (PEI) reference standard. The HBV genotype was determined by direct sequencing and phylogenetic analysis. Of 1292 samples, the distribution of genotype was 514 (39.78%) genotype B, 776 (60.06%) genotype C, 2 (0.16%) genotype D. The results of HBsAg and HBeAg quantification between the Architect and Elecsys assays were significantly correlated (HBsAg: r=0.939; HBeAg: r=0.987), independent of HBV genotype and treatment phase. The mean differences between the two methods (the log10 [Elecsys] - the log10 [Architect]) were 0.075log10 IU/mL and -0.149log10 PEIU/mL in quantifying HBsAg and HBeAg, respectively. This study demonstrates a high correlation between the Elecsys and the Architect assays in quantifying HBsAg and HBeAg, regardless of HBV genotype. Both the two assays can be used to monitor the HBsAg and HBeAg levels in patients with chronic hepatitis B.

Quantification of hepatitis B e antigen between Elecsys HBeAg and Architect HBeAg assays among patients infected with hepatitis B virus

BackgroundAmong patients infected with hepatitis B virus (HBV), quantification of hepatitis B e antigen (HBeAg) is accruing substantial clinical relevance as a marker for HBeAg-loss during treatment. No direct comparison has been made between assays that quantify HBeAg. ObjectivesTo compare the performance of HBeAg quantification (qHBeAg) between Architect and Elecsys HBeAg assays among 183 patients with chronic HBV infection (94 treatment-naïve HBV-monoinfected and 89 antiretroviral-experienced HIV-HBV co-infected). Study designqHBeAg was determined in Paul Erlich Institute Units (PEIU)/mL using previously designed protocols. Values were compared with correlation and linear regression. Bland–Altman analysis was used to compare mean differences (d¯) between Elecsys and Architect assays and limits of agreement (LOA) (±2 standard deviations [SD]). ResultsBetween-assay correlation was significant overall (r=0.970), yet stronger for qHBeAg<1000 (n=131) versus >1000PEIU/mL (n=52) as determined by the Elecsys assay (r=0.969 vs. 0.880, respectively). On average, the Elecsys assay reported qHBeAg at 13.3PEIU/mL lower than the Architect assay (LOA: −415.9, 389.3), while LOA between assays were much wider at higher levels (<1000: −198.2, 147.9; ≥1000PEIU/mL: −688.4, 721.5). Further analysis indicated that d¯ did not change substantially with respect to HBV genotype, precore mutation, and CD4+ cell count, regardless of HBeAg-level. Nevertheless, seven of eight patients with highly divergent between-assay results had HBV-DNA>2000IU/mL. ConclusionsElecsys and Architect assays report similar qHBeAg units with high correlation. Since qHBeAg was performed using an in-house approach, a commercially-available assay could reduce between-assay discrepancies, especially at higher HBeAg-levels.

Performance of the Elecsys Rubella IgG Assay in the Diagnostic Laboratory Setting for Assessment of Immune Status

Rubella in early pregnancy bears a high risk for congenital defects (e.g., cataracts, hearing loss, and heart disease) and for long-term sequelae in the newborn. Despite implementation of vaccination programs in many regions, the threat of devastating consequences from congenital rubella virus infection remains and careful screening of maternal immune status before and during pregnancy helps to reduce the risk. This study compared the performance of the Elecsys Rubella IgG assay with that of other assays routinely used for screening. Samples from 1,090 women undergoing routine antenatal care were tested using the Elecsys and Enzygnost Rubella IgG assays and the hemagglutination inhibition test. Samples with hemagglutination inhibition titers of <32 (n = 148) were additionally tested using the Vidas, AxSYM, Liaison, and Architect Rubella IgG assays. Agreement of qualitative results from the Elecsys, Enzygnost, and hemagglutination inhibition assays was good in all samples. All assays showed 100.0% specificity. In samples with hemagglutination inhibition titers of <32, the Elecsys, AxSYM, and Enzygnost assays showed higher sensitivity (>90.0%) than the other immunoassays (78.6 to 82.4%). The Elecsys assay reported significantly higher rubella virus IgG levels than the other immunoassays across the whole set of 1,090 samples, with the largest bias and deviation from limits of agreement in Bland-Altman analysis. In conclusion, the Elecsys assay is highly sensitive and specific with regard to qualitative results and suitable for routine automated screening. However, given the considerable variation between quantitative results from different immunoassays, testing methods should be documented and the same assay used throughout an individual's antenatal follow-up wherever possible.

Switching between parathormone (PTH) assays: the impact on the diagnosis of renal osteodystrophy

Clinical guidelines for decision-making in chronic kidney disease (CKD) consider parathormone (PTH) levels. The measured PTH values differ if novel full length PTH(1-84) assays are used instead of earlier intact iPTH assays. In this study we analyzed how the classification of CKD patients alters when iPTH assays are switched to PTH(1-84) assays. Plasma samples were collected prior to dialysis sessions from 110 consecutive CKD patients on maintenance hemodialysis. PTH levels were determined with iPTH assays (Elecsys, Architect and DiaSorin Liaison N-tact) and PTH(1-84) assays (Elecsys and Liaison). Using KDIGO guidelines patients were classified as being below, above and in the recommended target range (RTR) of PTH. The results of classification with different assays were evaluated and, a novel calculation method of RTR was implemented. The prevalence of patients with PTH in RTR is comparable with each assay, but the individual patients differed. PTH(1-84) Elecsys and Liaison assays classified more patients as being below RTR than iPTH Elecsys and Architect but not Liaison N-tact assay (27.3%, 22.7% vs. 41%, 31.8%, and 36.4%, respectively). In turn, PTH(1-84) Elecsys and Liaison assays identified less CKD patients with PTH above the RTR than iPTH except N-tact assays (6.4%, 10% vs. 16.3%, 19%, and 6.3%, respectively). Using our calculation method, our discrimination values for PTH(1-84) assays to achieve classification identical to that with iPTH Elecsys were lower than those recommended by the manufacturer. Current guidelines for the treatment of secondary hyperparathyroidism in CKD should consider the type of assays used for PTH measurement. Each laboratory should assess its own RTR for PTH tests to achieve comparable classification. The presented calculation is simple, it mimics an everyday situation, switching from one assay to another one, and provides useful RTR values for PTH tests.

Comparison of immunoassays for NTproBNP conducted on three analysis systems: Milliplex, Elecsys and RIA

ObjectivesThe aim of this study was to evaluate a Milliplex NTproBNP immunoassay and to compare its performance with the Roche Elecsys assay and an in house NTproBNP radioimmunoassay (RIA). Design and methodsSamples were analyzed for NTproBNP in all 3 assays following the manufacturer's instructions and/or our previously published methodologies. ResultsSimilar plasma concentrations and assay reproducibility were observed for the Roche assay and in house RIA. However, the Milliplex assay produced much lower concentrations than the other two assays (versus Roche Elecsys bias of −367.9pg/mL, (LOA −907.6 and 171.8)), and only quantified results for 63 of the 111 samples assessed. Of these 46 samples had acceptable errors of measurement (within sample coefficients of variation <20%) equating to 41% of the total samples measured. ConclusionsThe Milliplex assay, in its current form, does not produce results comparable with the Roche Elecsys 2010 assay or our in house RIA, and does not perform well as a quantitative assay. It may provide qualitative results (ie high, medium or low concentration), and serve as a rudimentary screening assay.

Elecsys Hepatitis B Surface Antigen Quantitative Assay: Performance Evaluation and Correlation with Hepatitis B Virus DNA during 96 Weeks of Follow-up in Chronic Hepatitis B Patients

BackgroundTreatment for chronic hepatitis B aims to suppress virus replication and virus sequestration in hepatocytes. Covalently closed circular (ccc) DNA is the template for transcription of viral genes and is responsible for viral persistence. However, limited data are available for quantification of hepatitis B surface antigen (HBsAg) in Korea.MethodsWe evaluated the Elecsys HBsAg II quant assay (Roche Diagnostics, USA) for within-run, between-run, and between-day precisions, linearity, carryover, and clinical specificity. In total, 156 serum samples were evaluated for correlation between HBsAg and hepatitis B virus (HBV) DNA. Serial samples were obtained from 10 patients at 0, 12, 24, 48, 72, and 96 weeks during follow-up.ResultsThe assay detected HBsAg in a linear range of 0.5-48,696 IU/mL. Within-run, between-run, and between-day CVs were 2.9-4.1%, 0-1.5%, and 1.5-4.9%, respectively. Cross-reactivity between potentially interfering substances was absent, and the carryover rate was 0.00002%. The correlation of measurements between the Elecsys assay and HBV DNA PCR was weak (r=0.438, P=0.002). For predicting virologic response, cutoff values of 10,275 IU/mL and 3,846 IU/mL at 12 and 24 weeks after treatment initiation showed positive predictive values of 77.1% and 85% and negative predictive values of 84.6% and 50%, respectively.ConclusionsThe Elecsys HBsAg II quant assay showed good performance for precision, linearity, carryover rate, and specificity. HBsAg level at baseline, 12 weeks, and 24 weeks after treatment initiation can predict virologic response, and the assay can be used for HBsAg quantification in clinical practice.

Cardiac Biomarker Responses to Dobutamine Stress Echocardiography in Healthy Volunteers and Patients with Coronary Artery Disease

To the Editor: Cardiac stress testing provides important diagnostic and prognostic information in ischemic heart disease (1). The sensitivity and specificity of stress testing are limited, however (2). If a circulating biomarker could reliably reflect the short-lived ischemia that occurs with stress testing and if differences in marker-release patterns could be associated with grades of risk for negative outcomes, one would expect the sensitivity, specificity, and overall utility of stress testing to improve substantially. High-sensitivity cardiac troponin assays have potential to be earlier markers of myocardial ischemia (3, 4). B-type natriuretic peptide signal peptide (BNPsp)1 is a recently discovered circulating biomarker (5). In the setting of ST-segment elevation myocardial infarction, BNPsp concentrations increase early, preceding myoglobin peaks. BNPsp has not been reported to date in less extreme forms of cardiac ischemia. We document the release of BNPsp, N-terminal pro–B-type natriuretic peptide (NT-proBNP), and troponin T as measured with a high-sensitivity assay (hsTnT) during dobutamine stress echocardiography (DSE) in patients with coronary artery disease (CAD) and in healthy volunteers. Blood samples were collected from 16 CAD patients and 10 healthy volunteers just before DSE and serially for 4 h. Plasma BNPsp was measured with a locally developed RIA (5). hsTnT and NT-proBNP concentrations were measured with commercially available Elecsys assays (Roche Diagnostics). …

Evaluation of the New Elecsys Toxo IgG Avidity Assay for Toxoplasmosis and New Insights into the Interpretation of Avidity Results

Detection and treatment of acute toxoplasmosis during pregnancy can avoid severe disease of the fetus. In this context, assessment of anti-Toxoplasma IgG avidity has been shown to exclude recent infection. The Elecsys Toxo IgG and IgM assays (Roche Diagnostics) have been validated for screening pregnant women and a new assay, Elecsys Toxo IgG Avidity, was recently developed. Our aims were to investigate the performance characteristics of this new avidity assay and explore whether additional information can be provided by avidity assays. The Elecsys assay was compared with the Vidas (bioMérieux) and Architect (Abbott) Avidity assays using two sets of serum samples (n = 291 and n = 255). The rate of general agreement between the Elecsys and Vidas assays was 74%, and that between the Elecsys and Architect assays was 83%. For 11% of the serum samples, avidity was high with the Vidas assay and within the gray zone with the Elecsys assay. None of the assays detected high-avidity antibodies in serum taken <4 months after infection. Avidity values of >90% were exclusively reported in sera taken >9 months after infection by the Elecsys and Architect assays. Almost all avidities of <19% with the Elecsys assay and <17% with the Architect assay corresponded to sera taken <3 and <2 months after infection, respectively. The Elecsys IgG Avidity assay can be used to exclude recent infection. New ways of interpreting the avidity result are also suggested: very high or low values could exclude infections within the last 9 months or help to confirm a recent infection, respectively. However, these potential interpretations require further investigation.

Clinical evaluation of new automated cytomegalovirus IgM and IgG assays for the Elecsys® analyser platform

Cytomegalovirus (CMV) is a leading cause of physical and neurological abnormalities in newborns. Hence, the diagnosis of CMV infection in pregnant women is necessary in order to allow appropriate management of their pregnancy. New assays have been developed for the Roche Elecsys® immunoassay platform that detect CMV-specific immunoglobulin (Ig)M and IgG, with the IgM assay designed to target IgM produced at the start of infection rather than IgM persisting later in infection. This study aimed to evaluate the performance of the new assays compared with other commercial kits widely distributed in laboratories. The performance of the Elecsys and comparator CMV IgM and IgG assays was assessed using 967 preselected patient samples characterised by CMV infection status, as well as being compared using 1,668 unselected clinical samples. The Elecsys CMV IgM and IgG assays performed consistently with comparator assays using the preselected samples. The Elecsys CMV IgM assay showed improved sensitivity compared with the Enzygnost® assay in primary infection (91.2 % vs. 79.4 %) and improved specificity over the Architect® assay in potentially cross-reacting samples (94.1 % vs. 82.4 %). The Elecsys IgM assay reported fewer positive results in the later stages of CMV infection compared with ETI-CYTOK-M ELISA, while the Elecsys IgG assay reported slightly fewer negative results in the early stages of infection compared with ETI-CYTOK-G ELISA. There was good agreement between Elecsys and comparator assays using unselected clinical samples (range 90.4-99.4 %). The Elecsys CMV IgM and IgG assays compare well with routinely used assays and are suitable for clinical use.