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  • Lundberg, Peter, et al. (författare)
  • 1H NMR determination of urinary betaine in patients with premature vascular disease and mild homocysteinemia
  • 1995
  • Ingår i: Clinical Chemistry. - 0009-9147 .- 1530-8561. ; 41:2, s. 275-283
  • Tidskriftsartikel (refereegranskat)abstract
    • Urinary N,N,N-trimethylglycine (betaine) and N,N-dimethylglycine (DMG) have been identified and quantified for clinical purposes by proton nuclear magnetic resonance (1H NMR) measurement in previous studies. We have assessed these procedures by using both one-dimensional (1-D) and 2-D NMR spectroscopy, together with pH titration of urinary extracts to help assign 1H NMR spectral peaks. The betaine calibration curve linearity was excellent (r = 0.997, P = 0.0001) over the concentration range 0.2-1.2 mmol/L, and CVs for replicate betaine analyses ranged from 7% (n = 10) at the lowest concentration to 1% (n = 9) at the highest. The detection limit for betaine was < 15 mumol/L. Urinary DMG concentrations were substantially lower than those of betaine. Urinary betaine and DMG concentrations measured by 1H NMR spectroscopy from 13 patients with premature vascular disease and 17 normal controls provided clinically pertinent data. We conclude that 1H NMR provides unique advantages as a research tool for determination of urinary betaine and DMG concentrations.
  • Aakre, K. M., et al. (författare)
  • Analytical Considerations in Deriving 99th Percentile Upper Reference Limits for High-Sensitivity Cardiac Troponin Assays: Educational Recommendations from the IFCC Committee on Clinical Application of Cardiac Bio-Markers
  • 2022
  • Ingår i: Clinical chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 68:8
  • Tidskriftsartikel (refereegranskat)abstract
    • The International Federation of Clinical Chemistry Committee on Clinical Application of Cardiac Bio-Markers provides evidence-based educational documents to facilitate uniform interpretation and utilization of cardiac biomarkers in clinical laboratories and practice. The committee's goals are to improve the understanding of certain key analytical and clinical aspects of cardiac biomarkers and how these may interplay in clinical practice. Measurement of high-sensitivity cardiac troponin (hs-cTn) assays is a cornerstone in the clinical evaluation of patients with symptoms and/or signs of acute cardiac ischemia. To define myocardial infarction, the Universal Definition of Myocardial Infarction requires patients who manifest with features suggestive of acute myocardial ischemia to have at least one cTn concentration above the sex-specific 99th percentile upper reference limit (URL) for hs-cTn assays and a dynamic pattern of cTn concentrations to fulfill the diagnostic criteria for MI. This special report provides an overview of how hs-cTn 99th percentile URLs should be established, including recommendations about prescreening and the number of individuals required in the reference cohort, how statistical analysis should be conducted, optimal preanalytical and analytical protocols, and analytical/biological interferences or confounds that can affect accurate determination of the 99th percentile URLs. This document also provides guidance and solutions to many of the issues posed.
  • Ahlqvist, Emma, et al. (författare)
  • Genetics of type 2 diabetes
  • 2011
  • Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 57:2, s. 241-254
  • Forskningsöversikt (refereegranskat)abstract
    • Background: Type 2 diabetes (T2D) is a complex disorder that is affected by multiple genetic and environmental factors. Extensive efforts have been made to identify the disease-affecting genes to better understand the disease pathogenesis, find new targets for clinical therapy, and allow prediction of disease.Content: Our knowledge about the genes involved in disease pathogenesis has increased substantially in recent years, thanks to genomewide association studies and international collaborations joining efforts to collect the huge numbers of individuals needed to study complex diseases on a population level. We have summarized what we have learned so far about the genes that affect T2D risk and their functions. Although more than 40 loci associated with T2D or glycemic traits have been reported and reproduced, only a minor part of the genetic component of the disease has been explained, and the causative variants and affected genes are unknown for many of the loci.Summary: Great advances have recently occurred in our understanding of the genetics of T2D, but much remains to be learned about the disease etiology. The genetics of T2D has so far been driven by technology, and we now hope that next-generation sequencing will provide important information on rare variants with stronger effects. Even when variants are known, however, great effort will be required to discover how they affect disease risk.
  • Ahmad, Shafqat, et al. (författare)
  • Adiposity and Genetic Factors in Relation to Triglycerides and Triglyceride-Rich Lipoproteins in the Women's Genome Health Study
  • 2018
  • Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 64:1, s. 231-241
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Previous results from Scandinavian cohorts have shown that obesity accentuates the effects of common genetic susceptibility variants on increased triglycerides (TG). Whether such interactions are present in the US population and further selective for particular TG-rich lipoprotein subfractions is unknown.METHODS: We examined these questions using body mass index (BMI) and waist circumference (WC) among women of European ancestry from the Women's Genome Health Study (WGHS) (n = 21840 for BMI; n = 19313 for WC). A weighted genetic risk score (TG-wGRS) based on 40 published TG-associated single-nucleotide polymorphisms was calculated using published effect estimates.RESULTS: Comparing overweight (BMI ≥ 25 kg/m2) and normal weight (BMI < 25 kg/m2) WGHS women, each unit increase of TG-wGRS was associated with TG increases of 1.013% and 1.011%, respectively, and this differential association was significant (Pinteraction = 0.014). Metaanalyses combining results for WGHS BMI with the 4 Scandinavian cohorts (INTER99, HEALTH2006, GLACIER, MDC) (total n = 40026) yielded a more significant interaction (Pinteraction = 0.001). Similarly, we observed differential association of the TG-wGRS with TG (Pinteraction = 0.006) in strata of WC (<80 cm vs ≥80 cm). Metaanalysis with 2 additional cohorts reporting WC (INTER99 and HEALTH2006) (total n = 27834) was significant with consistent effects (Pinteraction = 0.006). We also observed highly significant interactions of the TG-wGRS across the strata of BMI with very large, medium, and small TG-rich lipoprotein subfractions measured by nuclear magnetic resonance spectroscopy (all Pinteractions < 0.0001). The differential effects were strongest for very large TG-rich lipoprotein.CONCLUSIONS: Our results support the original findings and suggest that obese individuals may be more susceptible to aggregated genetic risk associated with common TG-raising alleles, with effects accentuated in the large TG-rich lipoprotein subfraction.
  • Alehagen, Urban, et al. (författare)
  • Prognostic Assessment of Elderly Patients with Symptoms of Heart Failure by Combining High-Sensitivity Troponin T and N-Terminal Pro-B-Type Natriuretic Peptide Measurements
  • 2010
  • Ingår i: CLINICAL CHEMISTRY. - : American Association for Clinical Chemistry; 1999. - 0009-9147 .- 1530-8561. ; 56:11, s. 1718-1724
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a useful biomarker in heart failure assessment, whereas measurement of cardiac troponin is central in the diagnosis of patients with acute coronary syndromes. This report examined the prognostic use of combining high-sensitivity cardiac troponin T (hs-cTnT) and NT-proBNP measurements in elderly patients presenting to a primary care center with symptoms associated with heart failure. METHODS: A total of 470 elderly patients (age range 65-86 years) presenting with symptoms of heart failure were recruited from primary healthcare. In addition to clinical examination and echocardiography, hs-cTnT and NT-proBNP plasma concentrations were measured. All patients were followed for 10 years, and cardiovascular mortality was registered. RESULTS: By use of the hs-cTnT assay, 80.4% of the population had plasma concentrations above the lower detection limit of the assay. Of those displaying a plasma concentration of hs-cTnT andgt;99th percentile of a healthy population, 43% also had an NT-proBNP concentration in the fourth quartile (andgt;507 ng/L). In the multivariate analysis, we observed a 2.5-fold increased risk for cardiovascular mortality in individuals with a plasma NT-proBNP concentration andgt;507 ng/L (P andlt; 0.0001). Conversely, patients with hs-cTnT andgt;99th percentile displayed an approximately 2-fold increased risk for cardiovascular mortality (P = 0.0002). Combining the 2 biomarkers, NT-proBNP concentrations andgt;507 ng/L with hs-cTnT andgt;99th percentile increased the risk 3-fold, even after adjustment for clinical variables such as age, sex, impaired estimated glomerular filtration rate, and anemia (P andlt; 0.0001). CONCLUSIONS: hs-cTnT and NT-proBNP measurements combined provide better prognostic information than using either biomarker separately in elderly patients with symptoms associated with heart failure.
  • Alehagen, Urban, 1951-, et al. (författare)
  • Utility of the amino-terminal fragment of pro-brain natriuretic peptide in plasma for the evaluation of cardiac dysfunction in elderly patients in primary health care
  • 2003
  • Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 49:8, s. 1337-1346
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The aims of this study were to measure the N-terminal fragment of pro-brain natriuretic peptide (proBNP) in plasma in medical conditions commonly found in primary care and to evaluate the utility of these measurements in identifying impaired cardiac function in elderly patients with symptoms associated with heart failure.Methods: We studied 415 patients (221 men and 194 women; mean age, 72 years) who had contacted a primary healthcare center for dyspnea, fatigue, and/or peripheral edema. One cardiologist evaluated the patients in terms of history, physical examination, functional capacity, electrocardiography, and suspicion of heart failure. Plasma N-terminal proBNP was measured by an in-house RIA. An ejection fraction ≤40% by Doppler echocardiography was regarded as reduced cardiac function. Abnormal diastolic function was defined as an abnormal mitral inflow defined as reduced ratio of peak early diastolic filling velocity to peak filling velocity at atrial contraction (E/A ratio), or as abnormal pulmonary venous flow pattern.Results: Patients with impaired functional capacity, impaired systolic function, and/or impaired renal function had significantly increased N-terminal proBNP concentrations. By multiple regression analysis, N-terminal proBNP concentrations were also influenced by ischemic heart disease, cardiac enlargement, and certain medications but not by increased creatinine. No gender differences were observed. Patients with isolated diastolic dysfunction attributable to relaxation abnormali-ties had lower concentrations than those with normal cardiac function, whereas those with pseudonormal E/A ratios or restrictive filling patterns had higher concentrations.Conclusions: Plasma N-terminal proBNP concentrations increase as a result of impaired systolic function, age, impaired renal function, cardiac ischemia and enlargement, and certain medications. Values are high in diastolic dysfunction with pseudonormal patterns, but not in patients with relaxation abnormalities. An increase in plasma N-terminal proBNP might be an earlier sign of abnormal cardiac function than abnormalities identified by currently used echocardiographic measurements.
  • Aomori, Tohru, et al. (författare)
  • Rapid Single-Nucleotide Polymorphism Detection of Cytochrome P450 (CYP2C9) and Vitamin K Epoxide Reductase (VKORC1) Genes for the Warfarin Dose Adjustment by the SMart-Amplification Process Version 2
  • 2009
  • Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 55:4, s. 804-812
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Polymorphisms of the CYP2C9 (cytochrome P450, family 2, subfamily C, polypeptide 9) gene (CYP2C9*2, CYP2C9*3) and the VKORC1 (vitamin K epoxide reductase complex, subunit 1) gene (-1639G>A) greatly impact the maintenance dose for the drug warfarin. Prescreening patients for their genotypes before prescribing the drug facilitates a faster individualized determination of the proper maintenance dose, minimizing the risk for adverse reaction and reoccurrence of thromboembolic episodes. With current methodologies, therapy can be delayed by several hours to 1 day if genotyping is to determine the loading dose. A simpler and more rapid genotyping method is required. METHODS: We developed a single-nucleotide polymorphism (SNP)-detection assay based on the SMart Amplification Process version 2 (SMAP 2) to analyze CYP2C9*2, CYP2C9*3, and VKORC1 -1639G>A polymorphisms. Blood from consenting participants was used directly in a closed-tube real-time assay without DNA purification to obtain results within 1 h of blood collection. RESULTS: We analyzed 125 blood samples by both SMAP 2 and PCR-RFLP methods. The results showed perfect concordance. CONCLUSIONS: The results validate the accuracy of the SMAP 2 for determination of SNPs critical to personalized warfarin therapy. SMAP 2 offers speed, simplicity of sample preparation, the convenience of isothermal amplification, and assay-design flexibility, which are significant advantages over conventional genotyping technologies. In this example and other clinical scenarios in which genetic testing is required for immediate and better-informed therapeutic decisions, SMAP 2-based diagnostics have key advantages.
  • Baxter, Douglas, et al. (författare)
  • Methylmercury measurement in whole blood by isotope-dilution GC-ICPMS with 2 sample preparation methods
  • 2007
  • Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:1, s. 111-116
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Despite its known toxicity, methylmercury is rarely measured directly in clinical studies; instead, conclusions are based on total mercury measurements. We have developed isotope-dilution-based methods for methylmercury-specific analysis of whole blood by coupled gas chromatography-inductively coupled plasma mass spectrometry (GC-ICPMS). Methods: We analyzed animal and human blood samples after alkaline digestion or extraction of methylmercury into dichloromethane and back extraction into water. Methylmercury was converted to the volatile ethyl derivative, purged, and trapped on a solid-phase collection medium, and then introduced into the GC-ICPMS system. Results: Limits of quantification were 0.4 and 0.03 mu g/L at a signal-to-noise ratio of 10 with the alkaline digestion and extraction methods, respectively. Extraction met our selected acceptable total error criterion, with an SD of 0.58 mu g/L at the critical maternal blood concentration of 5.8 mu g/L.Results obtained with alkaline digestion indicated the need for improved random analytical uncertainty, which was achieved by increasing the enrichment of the isotope dilution. For 37 blood samples, the mean (SD) proportion of total mercury present as methylmercury was 60 (27)%, range 6%-100%.Conclusions: The combination of extraction and isotope-dilution GC-ICPMS meets the requirements for use as a reference method for measuring methylmercury in whole blood.
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