bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid Detection of Aneuploidy (Trisomy 21) by Allele Quantification Combined with Melting Curves Analysis of Single-Nucleotide Polymorphism Loci
Authors: Pont-Kingdon Genevieve , Lyon Elaine 
Published: February 2004

AbstractBackground: Molecular approaches for the detection of chromosomal abnormalities will allow the development of rapid, cost-effective screening strategies. We present here a molecular alternative for the detection of aneuploidies and, more specifically, trisomy 21.Methods: We used the quantitative value of melting curve analysis of heterozygous genetic loci to establish a relative allelic count. The two alleles of a given single-nucleotide polymorphism (SNP) were differentiated by thermodynamic stability with a fluorescently labeled hybridization probe and were quantified by relative areas of derivative melting curves detected after fluorescence resonance energy transfer. Heterozygous SNPs provided internal controls for the assay.Results: We selected six SNPs, heterozygous in at least 30% of a random population, to form a panel of informative loci in the majority of a random population. After normalization to a heterozygous control, samples segregated into three categories; nontrisomic samples had mean allele ratios of 0.96–1.09, whereas trisomic samples had mean ratios of 1.84–2.09 or 0.46–0.61, depending on which allele was duplicated. Within-run mean CVs of ratios were 6.5–27%, and between-assay mean CVs were 13–24%.Conclusions: The use of melting curve analysis of multiple SNPs is an alternative to the use of small tandem repeats for the detection of trisomies. Because of the high density of SNPs, the approach may be specifically useful for very fine mapping of the regions of chromosome 21 that are critical for Down syndrome; it is also applicable to aneuploidies other than trisomy 21 and to specimens that are not amenable to cytogenetic analysis.
Negative Interference in Cardiac Troponin I Immunoassays from a Frequently Occurring Serum and Plasma Component
Authors: Eriksson Susann , Junikka Miia , Laitinen Päivi , Majamaa-Voltti Kirsi , Alfthan Henrik , Pettersson Kim 
Published: February 2004

AbstractBackground: Cardiac troponin I (cTnI) is a sensitive marker of cardiac injury, but cTnI assays, like other immunoassays, are susceptible to interferences. We evaluated the presence of interfering substances by measuring the recovery of cTnI added to samples from volunteers and from patients with acute coronary syndromes (ACS).Methods: We added a ternary complex of human cardiac troponin (30–500 μg/L) or cTnI from serum to samples from healthy volunteers and ACS patients. We measured cTnI with a two-site sandwich time-resolved immunofluorometric assay using two antibodies against epitopes in the central stable part of cTnI. We also analyzed 108 heparin-plasma samples from 16 ACS patients with this assay, with an assay based on four antibodies, and with two commercial cTnI assays, AxSYM and ACS:180.Results: In samples from both healthy persons and ACS patients, recoveries for our assay were 1–167% (range). Recoveries were increased by addition of an antibody with an epitope in the N-terminal region of cTnI to the solid phase and an antibody with an epitope in the C-terminal region as a second detection antibody. In 2 of 16 patients with ACS, normal cTnI concentrations found when measured with the original assay demonstrated clinically abnormal (up to 10-fold higher) results with the additional N- and C-terminal antibodies in the early phase of infarction. Both commercial cTnI assays also demonstrated clinically misleading, falsely low cTnI concentrations.Conclusions: Some yet unidentified, variable component, present in the blood from healthy volunteers and ACS patients, interferes with the binding of antibodies against epitopes in the central part of cTnI used in two commercial assays. Our approach to supplement the mid-fragment cTnI antibodies with antibodies in the N- and C-terminal parts of the molecule in an experimental assay represents a step in resolving this interferent.
Time-resolved Fluorescence Resonance Energy Transfer Assay for Point-of-Care Testing of Urinary Albumin
Authors: Qin Qiu-Ping , Peltola Olli , Pettersson Kim 
Published: February 2004

AbstractBackground: Microalbuminuria is an established early marker of diabetic nephropathy and an important cardiovascular risk factor in diabetes and hypertension. We aimed to develop a rapid point-of-care assay for the measurement of urine albumin.Methods: The competitive homogeneous assay used an albumin-specific monoclonal antibody labeled with a stable fluorescent europium chelate as donor and an albumin labeled with cyanine 5 (Cy5) as acceptor. The assay was performed at room temperature in single microtitration wells that contained all the required dry-form reagents. The close proximity between the two labels in the immune complex allowed fluorescence resonance energy to be transferred from the pulse-excited europium chelate to the acceptor Cy5. The emission of long-lived energy transfer signal from the sensitized Cy5 was measured at 665 nm with time-resolved fluorometry that eliminated short-lived background.Results: The assay procedure required 12 min for a 10-μL urine sample. The working range was from 10 to ∼320 mg/L, and the lower limit of detection was 5.5 mg/L. The within- and between-run CVs were 6.9–10% and 7.5–13%, respectively. Recovery was 103–122%. The assay correlated well (r2 = 0.98; n = 37) with a laboratory-based immunoassay, although mean (SD) results were 7 (29)% lower.Conclusions: The speed and ease of performance of this assay recommend it for near-patient use. The assay is the first to combine a fluorescence resonance energy transfer-type rapid competitive assay with an all-in-one dry reagent.
Infrared Spectroscopic Identification of β-Thalassemia
Authors: Liu Kan-Zhi , Tsang Kam Sze , Li Chi Kong , Shaw R Anthony , Mantsch Henry H 
Published: February 2004

AbstractBackground: The aim of this study was to investigate the potential of infrared (IR) spectroscopy as a fast and reagent-free adjunct tool in the diagnosis and screening of β-thalassemia.Methods: Blood was obtained from 56 patients with β-thalassemia major, 1 patient with hemoglobin H disease, and 35 age-matched controls. Hemolysates of blood samples were centrifuged to remove stroma. IR absorption spectra were recorded for duplicate films dried from 5 μL of hemolysate. Differentiation between the two groups of hemoglobin spectra was by two statistical methods: an unsupervised cluster analysis and a supervised linear discriminant analysis (LDA).Results: The IR spectra revealed changes in the secondary structure of hemoglobin from β-thalassemia patients compared with that from controls, in particular, a decreased α-helix content, an increased content of parallel and antiparallel β-sheets, and changes in the tyrosine ring absorption band. The hemoglobin from β-thalassemia patients also showed an increase in the intensity of the IR bands from the cysteine −SH groups. The unsupervised cluster analysis, statistically separating spectra into different groups according to subtle IR spectral differences, allowed separation of control hemoglobin from β-thalassemia hemoglobin spectra, based mainly on differences in protein secondary structure. The supervised LDA method provided 100% classification accuracy for the training set and 98% accuracy for the validation set in partitioning control and β-thalassemia samples.Conclusion: IR spectroscopy holds promise in the clinical diagnosis and screening of β-thalassemia.
Disease-related Metabolites in Culture Medium of Fibroblasts from Patients with d-2-Hydroxyglutaric Aciduria, l-2-Hydroxyglutaric Aciduria, and Combined d/l-2-Hydroxyglutaric Aciduria
Authors: Struys Eduard A , Verhoeven Nanda M , Roos Birthe , Jakobs Cornelis 
Published: February 2004

AbstractBackground: d-2-Hydroxyglutaric aciduria (D-2-HGA), l-2-hydroxyglutaric aciduria (L-2-HGA), and the combined d/l-2-hydroxyglutaric aciduria (D/L-2-HGA) are poorly understood organic acidurias. To investigate the usefulness of cultured human skin fibroblasts for both diagnostic and research purposes, we measured disease-related metabolites in the cell culture medium.Methods: We measured d-2-hydroxyglutarate (D-2-HG), l-2-hydroxyglutarate (L-2-HG), succinate, 2-ketoglutarate, and citrate in fibroblast cell medium by stable-isotope-dilution gas chromatography–mass spectrometry and glutamine, glutamic acid, and lysine with an amino acid analyzer. We used six cell lines from patients with D-2-HGA, two from patients with L-2-HGA, three from patients with D/L-2-HGA, and seven control cell lines. Culture medium was analyzed after a 96-h incubation period.Results: Culture media from cell lines from D-2-HGA patients contained D-2-HG at concentrations 5- to 30-fold higher than media from controls, whereas the concentration of L-2-HG in media was not increased. Media from L-2-HGA cell lines showed a fivefold increase in L-2-HG compared with controls. Media containing fibroblasts from D/L-2-HGA patients contained moderately increased amounts of both D-2-HG and L-2-HG. For all cell lines, succinate concentrations in the blank medium were higher than after 96 h of incubation with the exception of two of three D/L-2-HGA cell lines. Media of D-2-HGA cell lines had 2-ketoglutarate concentrations that were 40% of that for controls. Glutamic acid concentrations in media of these cell lines were 60% lower than in controls.Conclusions: Cell culture media from fibroblasts from patients with D-2-HGA, L-2-HGA, or D/L-2-HGA contain increased amounts the corresponding 2-HGs, demonstrating the suitability of fibroblasts for both diagnosis of and research concerning 2-HGAs.
Urinary Estrone Conjugate and Pregnanediol 3-Glucuronide Enzyme Immunoassays for Population Research
Authors: O’Connor Kathleen A , Brindle Eleanor , Holman Darryl J , Klein Nancy A , Soules Michael R , Campbell Kenneth L , Kohen Fortüne , Munro Coralie J , Shofer Jane B , Lasley Bill L , Wood James W 
Published: February 2004

Abstract
Background: Monitoring of reproductive steroid hormones at the population level requires frequent measurements, hormones or metabolites that remain stable under less than ideal collection and storage conditions, a long-term supply of antibodies, and assays useful for a range of populations. We developed enzyme immunoassays for urinary pregnanediol 3-glucuronide (PDG) and estrone conjugates (E1Cs) that meet these criteria.
Methods: Enzyme immunoassays based on monoclonal antibodies were evaluated for specificity, detection limit, parallelism, recovery, and imprecision. Paired urine and serum specimens were analyzed throughout menstrual cycles of 30 US women. Assay application in different populations was examined with 23 US and 42 Bangladeshi specimens. Metabolite stability in urine was evaluated for 0–8 days at room temperature and for 0–10 freeze-thaw cycles.
Results: Recoveries were 108% for the PDG assay and 105% for the E1C assay. Serially diluted specimens exhibited parallelism with calibration curves in both assays. Inter- and intraassay CVs were &lt;11%. Urinary and serum concentrations were highly correlated: r = 0.93 for E1C–estradiol; r = 0.98 for PDG–progesterone. All Bangladeshi and US specimens were above detection limits (PDG, 21 nmol/L; E1C, 0.27 nmol/L). Bangladeshi women had lower follicular phase PDG and lower luteal phase PDG and E1Cs than US women. Stability experiments showed a maximum decrease in concentration for each metabolite of &lt;4% per day at room temperature and no significant decrease associated with number of freeze-thaw cycles.
Conclusions: These enzyme immunoassays can be used for the field conditions and population variation in hormone metabolite concentrations encountered in cross-cultural research.
Screening for Interference in Immunoassays
Authors: Emerson Jane F , Ngo Gilda , Emerson Scott S 
Published: February 2004

AbstractBackground: The presence of interfering substances in patient samples submitted for immunoassay cannot be reliably anticipated. We therefore evaluated three interference screening techniques and estimated the prevalence of interfering substances as defined by positive outcomes with these protocols.Methods: We evaluated 160 samples for the presence of substances that may interfere with four immunoassays (40 samples for each): thyroid-stimulating hormone, prostate-specific antigen, β-human chorionic gonadotropin, and cortisol. Interference was defined by nonlinear responses with serial dilution, discrepant results after pretreatment with heterophile blocking reagent (HBR), and positive reactions on a mouse-antibody-negative control reaction (Tandem ICON® ImmunoConcentration HCG). Criteria for declaring significant discrepant results were based on a Z-score computed using the assay CV. The McNemar test was used to compare the prevalence of discrepancies across the three screening techniques. The association between type of immunoassay and prevalence of discrepant results was determined by a modified Pearson χ2 statistic.Results: Five of the 160 samples [3.1%; 95% confidence interval (CI), 1.0–7.1%] screened positive with the ICON. Seventy-two of the 148 samples with informative serial dilutions (48.6%; 95% CI, 40.4–57.0%) had at least one discrepant result at higher dilutions. After pretreatment with HBR, 53 of the 140 samples (38%; 95% CI, 29.8–46%) were discrepant. Only 48 of the 140 samples with informative measurements for all three screening techniques (34%; 95% CI, 26–43%) were negative by all three. The prevalence of positive screens varied significantly by type of immunoassay (P &lt;0.0001) for both HBR and serial dilution. Only 3% (0.8–7%) of the samples tested with HBR showed a change from normal to abnormal or the reverse after treatment.Conclusions: Introducing a protocol based on any of these three techniques into the immunochemistry laboratory to prescreen for interfering substances is not warranted. The evaluation of specimens for the presence of interfering anti-animal antibodies should be reserved for cases in which clinical history or suspicious results indicate the need.
Optimal Sampling Strategies to Assess Inulin Clearance in Children by the Inulin Single-Injection Method
Authors: van Rossum Lyonne K , Mathot Ron A A , Cransberg Karlien , Vulto Arnold G 
Published: February 2004

AbstractBackground: Glomerular filtration rate in patients can be determined by estimating the plasma clearance of inulin with the single-injection method. In this method, a single bolus injection of inulin is administered and several blood samples are collected. For practical and convenient application of this method in children, it is important that a minimal number of samples are drawn. The aim of this study was to develop and validate sampling strategies with fewer samples for reliable prediction of inulin clearance in pediatric patients by the inulin single-bolus-injection method.Methods: Complete inulin plasma concentration-time curves of 154 patients were divided into an index (n = 100) and a validation set (n = 54). A population pharmacokinetic model was developed for the index set. Optimal sampling times were selected based on D-optimality theory. For the validation set, Bayesian estimates of clearance were generated using the derived population parameters and concentrations at two to four sampling times. Bayesian estimates of clearance were compared with the individual reference values of clearance.Results: The strategies with samples taken at 10/30/90/240 min, 10/30/240 min, 10/90/240 min, 30/90/240 min, and 90/240 min allowed accurate prediction of inulin clearance (bias &lt;3% and not significantly different from 0; imprecision &lt;15%).Conclusions: Strategies involving two to four samples, including a sample at 240 min after administration of inulin, in the inulin single-injection method allow accurate prediction of inulin clearance in pediatric patients. Even one blood sample at 240 min showed acceptable performance. The proposed strategies are practical and convenient to children, and reduce repetitive blood sampling without compromising accuracy.
Practical Considerations for the Measurement of Free Light Chains in Serum
Authors: Tate Jillian R , Gill Devinder , Cobcroft Ralph , Hickman Peter E 
Published: February 2004

AbstractBackground: A new immunoassay for free light chain measurements has been reported to be useful for the diagnosis and monitoring of monoclonal light chain diseases and nonsecretory myeloma. We describe experience with and some potential pitfalls of the assay.Methods: The assay was assessed for precision, sample type and stability, recovery, and harmonization of results between two analyzers on which the reagents are used. Free-light-chain concentrations were measured in healthy individuals (to determine biological variation), patients with monoclonal gammopathy of undetermined significance, myeloma patients after autologous stem cell transplants, and patients with renal disease.Results: Analytical imprecision (CV) was 6–11% for κ and λ free-light-chain measurement and 16% for the calculated κ/λ ratio. Biological variation was generally insignificant compared with analytical variation. Despite the same reagent source, values were not completely harmonized between assay systems and may produce discordant free-light-chain ratios. In some patients with clinically stable myeloma, or post transplantation, or with monoclonal gammopathy of undetermined significance, free-light-chain concentration and ratio were within the population reference interval despite the presence of monoclonal intact immunoglobulin in serum. In other patients with monoclonal gammopathy of undetermined significance, values were abnormal although there was no clinical evidence of progression to multiple myeloma.Conclusions: The use of free-light-chain measurements alone cannot differentiate some groups of patients with monoclonal gammopathy from healthy individuals. As with the introduction of any new test, it is essential that more scientific data about use of this assay in different subject groups are available so that results can be interpreted with clinical certainty.
Preanalytic and Analytic Sources of Variations in C-reactive Protein Measurement: Implications for Cardiovascular Disease Risk Assessment
Authors: Ledue Thomas B , Rifai Nader 
Published: February 2004

AbstractBackground: C-reactive protein (CRP) is a widely recognized indicator of inflammation and is known to play an important role in atherogenesis. Recent prospective studies have demonstrated that increased CRP concentrations within the reference interval are a strong predictor of myocardial infarction, stroke, sudden cardiac death, and peripheral vascular disease in apparently healthy adults. On the basis of available evidence, the American Heart Association and the CDC have issued guidelines for the utility of CRP in the primary prevention of coronary heart disease and in patients with stable coronary disease or acute coronary syndromes. Nevertheless, there remains considerable work to optimize the utility of this marker for risk assessment.Issues: Most traditional CRP tests designed to monitor acute and chronic inflammation have inadequate sensitivity for risk stratification of coronary disease. Thus, manufacturers have had to develop tests with higher sensitivity. Because an individual’s CRP concentration will be interpreted according to fixed cut-points, issues related to the preanalytic and analytic components of CRP measurement must be considered and standardized where possible to avoid potential misclassification of cardiovascular risk.Conclusions: Efforts to define performance criteria for high-sensitivity CRP applications coupled with growing awareness of the physiologic aspects of CRP most likely will lead to refinements in standardization, improved performance in quality-assessment schemes, and enhanced risk prediction.
Time Course of Early and Late Changes in Plasma DNA in Trauma Patients
Authors: Lam Nicole Y L , Rainer Timothy H , Chan Lisa Y S , Joynt Gavin M , Lo Y M Dennis 
Published: February 2004

AbstractBackground: Cell-free DNA concentrations increase in the circulation of patients after trauma and may have prognostic potential, but little is know concerning the temporal changes or clearance of the DNA or its relationships with posttraumatic complications. We investigated temporal changes in plasma DNA concentrations in patients after trauma with use of real-time quantitative PCR.Methods: Serial plasma samples were taken from two trauma populations. In the first study, samples were collected every 20 min from 25 patients within the first 3 h of trauma. In the second study, samples were collected every day from 36 other trauma patients admitted to the intensive care unit (ICU).Results: In the first study, plasma DNA was increased within 20 min of injury and was significantly higher in patients with severe injury and in patients who went on to develop organ failure. In patients with less severe injuries, plasma DNA concentrations decreased toward reference values within 3 h. In the second study, plasma DNA concentrations were higher in patients who developed multiple organ dysfunction syndrome between the second and fourth days of admission than in patients who did not develop the syndrome. In patients who remained in the ICU with continuing organ dysfunction, plasma DNA remained higher than in healthy controls even at 28 days after injury. Most survivors with multiple organ dysfunction syndrome showed an initial very high peak followed by a prolonged smaller increase.Conclusions: Plasma DNA concentrations increase early after injury and are higher in patients with severe injuries and in those who develop organ failure. Increased plasma DNA persists for days after injuries, especially in patients with multiple organ dysfunction syndrome.
Increased Homocysteine and S-Adenosylhomocysteine Concentrations and DNA Hypomethylation in Vascular Disease
Authors: Castro Rita , Rivera Isabel , Struys Eduard A , Jansen Erwin E W , Ravasco Paula , Camilo Maria Ermelinda , Blom Henk J , Jakobs Cornelis , Tavares de Almeida Isabel 
Published: February 2004

Abstract
Background: The pathogenic mechanism of homocysteine’s effect on cardiovascular risk is poorly understood. Recent studies show that DNA hypomethylation induced by increases in S-adenosylhomocysteine (AdoHcy), an intermediate of Hcy metabolism and a potent inhibitor of methyltransferases, may be involved in homocysteine-related pathology.
Methods: We measured fasting plasma total Hcy (tHcy), AdoHcy, and S-adenosylmethionine (AdoMet) and methylation in leukocytes in 17 patients with vascular disease and in 15 healthy, age- and sex-matched controls.
Results: Patient with vascular disease had significantly higher plasma tHcy and AdoHcy concentrations and significantly lower plasma AdoMet/AdoHcy ratios and genomic DNA methylation. AdoMet concentrations were not significantly different between the two groups. More than 50% of the patients fell into the highest quartiles of plasma tHcy, AdoHcy, and [3H]dCTP incorporation/μg of DNA (meaning the lowest quartile of DNA methylation status) and into the lowest quartile of the AdoMet/AdoHcy ratios of the control group. Plasma tHcy was significantly correlated with plasma AdoHcy and AdoMet/AdoHcy ratios (n = 32; P &lt; 0.001). DNA methylation status was significantly correlated with plasma tHcy and AdoHcy (n = 32; P &lt; 0.01) but not with plasma AdoMet/AdoHcy ratios.
Conclusion: Global DNA methylation may be altered in vascular disease, with a concomitant increase in plasma tHcy and AdoHcy.