κ and λ urine free light chains: a new method for quantification.

BACKGROUND: Immunofixation electrophoresis of urinary proteins, coupled with densitometric analysis, is the gold standard method for determining urinary monoclonal free light chains (FLCs), i.e. Bence Jones protein. Recently, immunochemical methods have been developed for Bence Jones protein quantification, but no such method has been widely adopted. This study evaluated a new antibody-based immunoturbidimetry method for urinary FLC quantification, using immunofixation electrophoresis as reference. METHODS: κ and λ FLCs were measured in urine specimens from 95 (training cohort) and 103 (testing cohort) patients by both immunofixation electrophoresis and immunoturbidimetry. RESULTS: There was almost perfect concordance in the training cohort between the new immunoturbidimetry assay and immunofixation electrophoresis and substantial agreement, with Cohen kappa of 0.85 and 0.75, for κ and λ FLC determination, respectively. Results were confirmed in the testing cohort, where Cohen kappa was 0.86 for κ and 0.94 for λ FLCs. The κ FLC assay had 88% sensitivity and 98%-100% specificity; the λ FLC assay had 94% and 96% sensitivity and 91% and 99% specificity in the training and testing cohorts, respectively. CONCLUSIONS: The new immunochemical method has a satisfactory performance and almost perfect agreement with immunofixation electrophoresis and gives the advantage of FLC quantification.

Evaluation of a Novel Anti-H. pylori Antibody Detection Kit by Latex Turbidimetric Immunoassay.

BACKGROUND: While all modalities used for diagnosis of Helicobacter pylori (H. pylori) have demonstrated sufficient sensitivity and specificity, each test has advantages and limitations. The serum test for anti-H. pylori antibody with the latex method is noninvasive, easy, and inexpensive; it is thus a useful tool for mass-screening for H. pylori. In this study, we evaluated the utility of a newly developed latex kit, in comparison with other serum diagnostic kits based on enzyme-linked immunosorbent assay (ELISA). METHODS: In total, 187 subjects (77: H. pylori-positive, 75: H. pylori-negative, 35: previous infection with H. pylori) seen at Oita University Hospital during the period from January 1988 to September 2014 were enrolled in the study. All subjects were evaluated with 4 types of serum H. pylori antibody kits. One modality was based on the use of latex (Denka Kit, Denka Seiken Co., Ltd., Tokyo, Japan). Three kits were based on the use of ELISA. The E-Plate II Eiken (Eiken Chemical Co., Ltd., Tokyo, Japan) is henceforth referred to as Kit A. The Premier H. pylori kit (Meridian Bioscience, Inc., USA) is referred to as Kit B. The Platelia H. pylori IgG (Bio-Rad, Marnes-la-Coquette, France) is referred to as Kit C. RESULTS: Evaluation of 152 study participants, including some who were positive for H. pylori and some who were negative, sensitivity, specificity, and accuracy values were as follows: for the Denka kit, these values were, respec-tively, 92.2%, 93.3%, and 92.8%. For Kit A, these values were 88.3%, 100.0%, and 194.1%. For Kit B, these values were 98.7%, 76.0%, and 87.5%. For Kit C, these values were 98.7%, 80.0%, and 89.5%. The specificity of Kit A was > 90%. Sensitivity was > 90% for Kits B and C. For the Denka kit, both sensitivity and specificity were > 90%. Among the 35 subjects previously infected with H. pylori, the rate of positive diagnosis was 48.6% (17/35) with the Denka kit, 17.1% (6/35) with Kit A, 54.3% (19/35) with Kit B, and 54.3% (19/35) with Kit C. The rate of positive diagnosis was significantly higher with the Denka kit than with Kit A (p < 0.05). CONCLUSIONS: An assay based on use of the latex method, H. pylori-latex Seiken, demonstrated satisfactory sensitivity and specificity for detecting serum levels of H. pylori antibody. The performance of this kit was equivalent to that of ELISA kits currently used for the same purpose. This kit is therefore considered to be extremely suitable for diagnosis of H. pylori and mass-screening of patients at high risk for gastric cancer.

Association Between Increased Levels of Cystatin C and the Development of Cardiovascular Events or Mortality: A Systematic Review and Meta-Analysis / Associação entre Níveis Elevados de Cistatina C e o Desenvolvimento de Eventos Cardiovasculares ou Mortalidade: Uma Revisão Sistemática e Meta-Análise

Abstract Background: Cystatin C seems promising for evaluating the risk of cardiovascular events and mortality. Objective: To evaluate the association between high levels of cystatin C and the development of cardiovascular events or mortality. Methods: The articles were selected in the Medline/PubMed, Web of Science, and Scielo databases. The eligibility criteria were prospective cohort observational trials that assessed the association of high serum levels of cystatin C with the development of cardiovascular events or mortality in individuals with normal renal function. Only studies that evaluated the mortality outcome compared the fourth with the first quartile of cystatin C and performed multivariate Cox's proportional hazard regression analysis were included in the meta-analysis. A p value < 0,05 was considered significant. Results: Among the 647 articles found, 12 were included in the systematic review and two in the meta-analysis. The risk of development of adverse outcomes was assessed by eight studies using the hazard ratio. Among them, six studies found an increased risk of cardiovascular events or mortality. The multivariate regression analysis was performed by six studies, and the risk of developing adverse outcomes remained significant after the analysis in four of these studies. The result of the meta-analysis [HR = 2.28 (1.70-3.05), p < 0.001] indicated that there is a significant association between high levels of cystatin C and the risk of mortality in individuals with normal renal function. Conclusion: There is a significant association between high levels of cystatin C and the development of cardiovascular events or mortality in individuals with normal renal function.

Resumo Fundamento: A cistatina C tem-se mostrado promissora para avaliação do risco de eventos cardiovasculares e mortalidade. Objetivo: Avaliar a associação entre níveis elevados de cistatina C e o desenvolvimento de eventos cardiovasculares ou mortalidade. Métodos: A seleção dos artigos foi realizada por meio das bases de dados Medline/PubMed, Web of Science e Scielo. Os critérios de elegibilidade foram estudos observacionais de coorte prospectivos que avaliaram a associação entre níveis séricos elevados de cistatina C e o desenvolvimento de eventos cardiovasculares ou mortalidade em indivíduos com função renal normal. Apenas os estudos que avaliaram o desfecho mortalidade, que compararam o quarto com o primeiro quartil de cistatina C e que realizaram análise de regressão multivariada de riscos proporcionais de Cox foram incluídos na meta-análise. Foi considerado significativo o valor p < 0,05. Resultados: Dentre os 647 artigos encontrados, 12 foram incluídos na revisão sistemática e dois na meta-análise. O risco de desenvolvimento dos desfechos adversos foi avaliado por oito estudos por meio do cálculo do hazard ratio. Dentre estes, seis estudos encontraram um maior risco de eventos cardiovasculares ou mortalidade. A análise de regressão multivariada foi realizada por seis destes estudos, e o risco de desenvolvimento dos desfechos adversos permaneceu significativo após realização desta análise em quatro destes estudos. O resultado da meta-análise [HR = 2,28 (1,70-3,05), p < 0,001] indicou que há uma associação significativa entre níveis elevados de cistatina C e o risco de mortalidade nos indivíduos com função renal normal. Conclusão: Há uma associação significativa entre níveis elevados de cistatina C e o desenvolvimento de eventos cardiovasculares ou mortalidade em indivíduos com função renal normal.

Association Between Increased Levels of Cystatin C and the Development of Cardiovascular Events or Mortality: A Systematic Review and Meta-Analysis.

BACKGROUND: Cystatin C seems promising for evaluating the risk of cardiovascular events and mortality. OBJECTIVE: To evaluate the association between high levels of cystatin C and the development of cardiovascular events or mortality. METHODS: The articles were selected in the Medline/PubMed, Web of Science, and Scielo databases. The eligibility criteria were prospective cohort observational trials that assessed the association of high serum levels of cystatin C with the development of cardiovascular events or mortality in individuals with normal renal function. Only studies that evaluated the mortality outcome compared the fourth with the first quartile of cystatin C and performed multivariate Cox's proportional hazard regression analysis were included in the meta-analysis. A p value < 0,05 was considered significant. RESULTS: Among the 647 articles found, 12 were included in the systematic review and two in the meta-analysis. The risk of development of adverse outcomes was assessed by eight studies using the hazard ratio. Among them, six studies found an increased risk of cardiovascular events or mortality. The multivariate regression analysis was performed by six studies, and the risk of developing adverse outcomes remained significant after the analysis in four of these studies. The result of the meta-analysis [HR = 2.28 (1.70-3.05), p < 0.001] indicated that there is a significant association between high levels of cystatin C and the risk of mortality in individuals with normal renal function. CONCLUSION: There is a significant association between high levels of cystatin C and the development of cardiovascular events or mortality in individuals with normal renal function.

Validation of the STA-Liatest DDi assay for exclusion of proximal deep vein thrombosis according to the latest Clinical and Laboratory Standards Institute/Food and Drug Administration guideline: results of a multicenter management study.

: Recommended strategy for venous thromboembolism (VTE) diagnosis includes the use of sensitive D-dimer (DDi) assays along with pretest probability (PTP) assessment. The Clinical and Laboratory Standards Institute (CLSI) recently issued a guideline (US FDA endorsed) on DDi in VTE exclusion. Such guideline specifies the ideal D-dimer assay characteristics and target population. Demonstrate STA-LiatestD-Di performance combined with a PTP score for proximal deep vein thrombosis (pDVT) exclusion in a CLSI compliant study. International, multicenter, prospective nonrandomized, noninterventional clinical outcome management study conducted in a standard-of-care setting. DDi was measured in DVT-suspected consecutive low/moderate PTP outpatients, without conditions possibly impacting DDi values independently of thrombosis presence (age >80, pregnancy, postoperative, cancer) using a 0.5 µg/ml (FEU) threshold for DVT exclusion. Results were used to determine test performance. One thousand two hundred and thirty-four patients (17 centers) signed informed consent. Nine hundred and eighty (mean age: 55) with valid results (494 negative DDi) completed the study (DVT prevalence: 8.7%). STA-LiatestD-Di performance exceeded CLSI/FDA requirements: sensitivity: 100% (95% CI 95.8-100%), NPV: 100% (95% CI 99.3-100%). STA-LiatestD-Di associated with PTP score showed excellent performance for pDVT exclusion, as recently demonstrated for pulmonary embolism. The assay allows safe VTE exclusion, avoiding unnecessary imaging tests.

Diagnostic Accuracy of Latex Agglutination Turbidimetric Immunoassay in Screening Adolescents for Helicobacter pylori Infection in Japan.

BACKGROUND/AIMS: Serologic tests are commonly used for screening Helicobacter pylori infection because they not only provide quick results but also are inexpensive. A new latex agglutination serum antibody assay (LZ test) has been developed and it is expected to be as effective as conventional assays. This study aimed to calculate a reliable cutoff value for the LZ test and to estimate the sensitivity and specificity of the cutoff value in screening adolescents for H. pylori infection in Japan. METHODS: We screened junior high school students in Akita Prefecture, Japan, for H. pylori infection. We used the data of 213 such students who underwent H. pylori stool antigen (HpSA) tests in 2016. The students who had positive results with HpSA tests were diagnosed with H. pylori infection. Of the 213 students, 209 underwent the LZ test. RESULTS: The prevalence rate of H. pylori infection was 3.8% (8/209). The area under the curve for the LZ test was 0.88. The cutoff value of the LZ test was determined to be 3.1 U/mL. At this value, the sensitivity and specificity were 87.5 and 91.5%, respectively. CONCLUSION: The accuracy of the LZ test in adolescents was well balanced for sensitivity and specificity as well as for tolerable results.

First two-reagent vitamin D assay for general clinical chemistry.

BACKGROUND: Vitamin D is a lipid-soluble molecule that plays key physiological roles in the metabolism of calcium, phosphate and magnesium. Recent studies show that deficiency in vitamin D is linked to cardiovascular diseases, autoimmune diseases and cancer. As a result, regular monitoring of 25-OH vitamin D (the main circulating form of vitamin D) is becoming essential. Current 25-OH vitamin D testing methodologies are cumbersome (too many reagents, long incubation times, phase separation) and are not compatible with general clinical chemistry platforms. Here, we report on a novel method to detect 25-OH vitamin D that is fast (results in 10 min or less), simple (two reagents) and compatible with virtually all general clinical chemistry analyzers. METHODS: An immunoturbidimetric assay for 25-OH vitamin D (the Diazyme EZ Vitamin D Assay) has been developed using nanoparticles and vitamin D-specific antibodies. The performance of the assay kit, which consists of two reagents and five calibrators, was tested on the Beckman AU680 analyzer (AU680). RESULTS: The new assay was precise, sensitive (LOD = 7.2 nmol/L), linear (up to 390.1 nmol/L) and correlated strongly (R2 > 0.95) with major commercial 25-OH vitamin D assays. Additionally, the assay was found to be the fastest to date, with the first results obtained within 10 min. Throughput on the AU680 was estimated at over 300 tests per hour. CONCLUSIONS: The newly developed 25-OH vitamin D assay is fast, precise and accurate. It can be run on most general chemistry analyzers. This assay aims at providing vitamin D-testing capabilities to all clinical chemistry laboratories.

A sensitive three monoclonal antibodies based automatic latex particle-enhanced turbidimetric immunoassay for Golgi protein 73 detection.

Golgi protein 73 (GP73) is a novel and potential marker for diagnosing hepatocellular carcinoma (HCC) that has been found to be abnormally elevated in liver disease. A latex particle-enhanced turbidimetric immunoassay (LTIA) was recently introduced and licensed for application in a variety of automated clinical chemistry analyzers. However, no studies have reported sufficient data on analytical performance of this method when using 3 monoclonal antibodies for GP73 measurement. The experimental conditions were firstly optimized and range of linearity, diagnostic potential, clinical relevance were compared with the LTIA based on polyclonal antibodies and ELISA. Dilution tests for the LTIA using 3 monoclonal antibodies produced a calibration curve from 10 to 350 ng/mL while the polyclonal antibodies produced the curve from 20 to 320 ng/mL. The detection limit was achieved at 1.82 ng/mL concentration. Within-run CV was obtained in the range of 1.5-2.9% and ROC curves indicated sensitivity and specificity of the LTIA based on 3 monoclonal antibodies were 96.7% and 93.3%, respectively, higher than for the polyclonal antibodies (94.6% and 72.4%) and ELISA (70.0% and 83.3%). Therefore, the LTIA assay based on 3 monoclonal antibodies is thus applicable in quantification of GP73 concentration in automated biochemistry analyzers.