| 1. |
- Lundberg, Peter, et al.
(författare)
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1H NMR determination of urinary betaine in patients with premature vascular disease and mild homocysteinemia
- 1995
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Ingår i: Clinical Chemistry. - 0009-9147 .- 1530-8561. ; 41:2, s. 275-283
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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.
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| 2. |
- Aakre, K. M., et al.
(författare)
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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
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Ingår i: Clinical chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 68:8, s. 1022-1030
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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.
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| 3. |
- Aakre, Kristin M, et al.
(författare)
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Lower Limits for Reporting High-Sensitivity Cardiac Troponin Assays and Impact of Analytical Performance on Patient Misclassification.
- 2024
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Ingår i: Clinical chemistry. - 0009-9147 .- 1530-8561. ; 70:3, s. 497-505
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Tidskriftsartikel (refereegranskat)abstract
- Cardiac troponin measurements are indispensable for the diagnosis of myocardial infarction and provide useful information for long-term risk prediction of cardiovascular disease. Accelerated diagnostic pathways prevent unnecessary hospital admission, but require reporting cardiac troponin concentrations at low concentrations that are sometimes below the limit of quantification. Whether analytical imprecision at these concentrations contributes to misclassification of patients is debated.The International Federation of Clinical Chemistry Committee on Clinical Application of Cardiac Bio-Markers (IFCC C-CB) provides evidence-based educational statements on analytical and clinical aspects of cardiac biomarkers. This mini-review discusses how the reporting of low concentrations of cardiac troponins impacts on whether or not assays are classified as high-sensitivity and how analytical performance at low concentrations influences the utility of troponins in accelerated diagnostic pathways. Practical suggestions are made for laboratories regarding analytical quality assessment of cardiac troponin results at low cutoffs, with a particular focus on accelerated diagnostic pathways. The review also discusses how future use of cardiac troponins for long-term prediction or management of cardiovascular disease may require improvements in analytical quality.Clinical guidelines recommend using cardiac troponin concentrations as low as the limit of detection of the assay to guide patient care. Laboratories, manufacturers, researchers, and external quality assessment providers should extend analytical performance monitoring of cardiac troponin assays to include the concentration ranges applicable in these pathways.
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| 4. |
- Abrahamsson, Per-Anders, et al.
(författare)
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Radioimmunoassay of beta-microseminoprotein, a prostatic-secreted protein present in sera of both men and women
- 1989
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Ingår i: Clinical Chemistry. - 0009-9147. ; 35:7, s. 1497-1503
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Tidskriftsartikel (refereegranskat)abstract
- We describe a simple radioimmunoassay of beta-microseminoprotein, one of the three most abundant secretory proteins of the prostate gland. The detection limit of the assay is 1 microgram/L, and its precision, expressed as the total coefficient of variation, is less than 10% for values between 10 and 150 micrograms/L. Using this assay, we found that beta-microseminoprotein immunoreactivity was present in sera from both sexes at about the same concentration. The protein detected had the same molecular size on gel chromatography as the protein isolated from seminal plasma, and dilution curves for the sera paralleled that for the pure protein. The findings suggest that beta-microseminoprotein is present in serum of healthy subjects of both sexes and that it originates in tissue other than the prostate gland. The range of the serum concentration was 0-10.6 micrograms/L (median 4.1) for 51 healthy adult women and 1.1-14.7 micrograms/L (median 6.2) for 35 healthy adult men not older than 40 years. In males with prostatic cancer the concentration in serum was highly variable and often greatly increased. The concentration of beta-microseminoprotein was correlated with that of creatinine in serum, suggesting that the protein is eliminated--at least partly--from the circulation by glomerular filtration. Little of the protein was present in the urine of women. In urine from men the concentration was high and variable, probably because of local contribution from the prostate gland to the urethral urine.
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| 5. |
- Agardh, Carl-David, et al.
(författare)
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Association between urinary N-acetyl-beta-glucosaminidase and its isoenzyme patterns and microangiopathy in type 1 diabetes mellitus
- 1991
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Ingår i: Clinical Chemistry. - 0009-9147. ; 37:10 Pt 1, s. 1696-1699
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Tidskriftsartikel (refereegranskat)abstract
- Urinary N-acetyl-beta-glucosaminidase (NAG) and its isoenzymes (NAG A and NAG B) in samples from 87 type 1 diabetic patients and 40 apparently healthy reference subjects were studied with enzyme immunoassays. The diabetic patients had higher concentrations of urinary NAG than did the control subjects (P less than 0.01), but the isoenzyme pattern did not differ. There was a positive correlation between metabolic control (Hb A1c concentrations) and total NAG (P less than 0.01), NAG A (P less than 0.01), and NAG B (P less than 0.001). The diabetic patients were divided into three groups, depending on the degree of retinopathy. Subjects with severe forms of retinopathy did not have increased concentrations of urinary NAG unless they had concomitant nephropathy. The isoenzyme pattern was similar irrespective of degree of retinopathy or nephropathy. The results indicate that concentrations of urinary NAG are positively correlated to the degree of nephropathy, whereas there is no such correlation to the degree of retinopathy.
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| 6. |
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| 7. |
- Ahlqvist, Emma, et al.
(författare)
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Genetics of type 2 diabetes
- 2011
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 57:2, s. 241-254
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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.
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| 8. |
- Ahmad, Shafqat, et al.
(författare)
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Adiposity and Genetic Factors in Relation to Triglycerides and Triglyceride-Rich Lipoproteins in the Women's Genome Health Study
- 2018
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 64:1, s. 231-241
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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.
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| 9. |
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| 10. |
- Alehagen, Urban, et al.
(författare)
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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
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Ingår i: CLINICAL CHEMISTRY. - : American Association for Clinical Chemistry; 1999. - 0009-9147 .- 1530-8561. ; 56:11, s. 1718-1724
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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.
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