| 41. |
- Zegers, Ingrid, et al.
(författare)
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Characterization of the New Serum Protein Reference Material ERM-DA470k/IFCC: Value Assignment by Immunoassay
- 2010
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 56:12, s. 1880-1888
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The availability of a suitable matrix reference material is essential for standardization of the immunoassays used to measure serum proteins. The earlier serum protein reference material ERM-DA470 (previously called CRM470), certified in 1993, has led to a high degree of harmonization of the measurement results. A new serum protein material has now been prepared and its suitability in term of homogeneity and stability has been verified; after characterization, the material has been certified as ERM-DA470k/IFCC. METHODS: We characterized the candidate reference material for 14 proteins by applying a protocol that is considered to be a reference measurement procedure, by use of optimized immunoassays. ERM-DA470 was used as a calibrant. RESULTS: For 12 proteins [alpha(2) macroglobulin (A2M), alpha(1) acid glycoprotein (orosomucoid, AAG), alpha(1) antitrypsin (alpha(1)-protease inhibitor, AAT), albumin (ALB), complement 3c (C3c), complement 4 (C4), haptoglobin (HPT), IgA, IgG, IgM, transferrin (TRF), and transthyretin (TTR)], the results allowed assignment of certified values in ERM-DA470k/IFCC. For CRP, we observed a bias between the lyophilized and liquid frozen materials, and for CER, the distribution of values was too broad. Therefore, these 2 proteins were not certified in the ERM-DA470k/IFCC. Different value transfer procedures were tested (open and closed procedures) and found to provide equivalent results. CONCLUSIONS: A new serum protein reference material has been produced, and values have been successfully assigned for 12 proteins. (C) 2010 American Association for Clinical Chemistry
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| 42. |
- Zieba, Agata, et al.
(författare)
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Bright-Field Microscopy Visualization of Proteins and Protein Complexes by In Situ Proximity Ligation with Peroxidase Detection
- 2010
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 56:1, s. 99-110
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The in situ proximity ligation assay (PLA) allows a protein or protein complex to be represented as an amplifiable DNA molecule. Recognition is mediated by proximity probes consisting of antibodies coupled with oligonucleotides. Upon dual binding of the proximity probes, the oligonucleotides direct the formation of a circular DNA molecule, which is then amplified by rolling-circle replication. The localized concatemeric product is then detected with fluorescent probes. The in situ PLA enables localized detection of individual native proteins or interacting protein pairs in fixed cells or tissue sections, thus providing an important tool for basic and clinical research. METHODS: We used horseradish peroxidase (HRP)conjugated oligonucleotides to couple in situ PLA with enzymatic visualization of the localized detection event. RESULTS: We demonstrate the detection of protein complexes, both in cells and in tissue sections, and show that we can quantify the complexes with image-analysis software specially developed for recognizing HRP signals in bright-field microscopy images. We show that fluorescence and HRP signals produce equivalent results, both ill cultured cells and in tissue samples. CONCLUSIONS: The combination of in situ PLA with bright-field detection and automated image analysis allows the signals present to be Counted in an automated fashion and thus provides a sensitive and specific method for quantification of proteins and protein complexes with bright-field microscopy. With this approach, in situ PLA can be used without the requirement for expensive fluorescence microscopes, thereby avoiding problems with nonspecific fluorescence while maintaining compatibility with conventional histologic staining.
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| 43. |
- Åkerblom, Axel, 1977-, et al.
(författare)
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Cystatin C- and Creatinine-based Estimates of Renal Function and Their Value for Risk Prediction in Patients with Acute Coronary Syndrome : Results from the PLATelet Inhibition and Patient Outcomes (PLATO) Study
- 2013
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 59:9, s. 1369-1375
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Tidskriftsartikel (refereegranskat)abstract
- Background: The estimated glomerular filtration rate (eGFR) independently predicts cardiovascular (CV) death or myocardial infarction (MI), and can be estimated by creatinine and cystatin C concentrations. We evaluated two different cystatin C assays, alone or combined with creatinine, in patients with acute coronary syndromes.Methods: Plasma cystatin C, measured with assays from Gentian and Roche, and serum creatinine was analyzed in 16279 patients from the PLATelet inhibition and patient Outcomes trial. Pearson’s correlation and agreement (Bland–Altman) between methods was evaluated. Prognostic value in relation to CV death or MI during one year of follow up was evaluated by multivariable logistic regression analysis including clinical variables and biomarkers, c-statistics and relative Integrated Discrimination Improvement (IDI).Results: Median cystatin C concentrations (interquartile intervals) were 0.83 (0.68 - 1.01) mg/L (Gentian) and 0.94 (0.80 - 1.14) mg/L (Roche). Overall correlation was 0.86 (95% confidence interval 0.85-0.86). The level of agreement was ±0.39mg/L (±2 standard deviations) (n=16279).The area under curve (AUC) in the multivariable risk prediction model with cystatin C (Gentian, Roche) or Chronic Kidney Disease - Epidemiology (CKD-EPI) added was 0.6914, 0.6913 and 0.6932. Corresponding relative IDIs were 2.96%, 3.86% and 4.68%, respectively (n=13050). Addition of eGFR by the combined creatinine-cystatin C equation yielded AUC of 0.6923(Gentian) and 0.6924(Roche) with relative IDIs of 3.54% and 3.24% respectively.Conclusions: Despite differences in cystatin C concentrations, overall correlation between the Gentian and Roche assays was good while agreement was moderate. The combined creatinine-cystatin C equation did not outperform risk prediction compared to CKD-EPI.
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| 44. |
- Åkerblom, Axel, 1977-, et al.
(författare)
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Cystatin C and Estimated Glomerular Filtration Rate as Predictors for Adverse Outcome in Patients with ST-Elevation and Non-ST-Elevation Acute Coronary Syndromes : Results from the Platelet Inhibition and Patient Outcomes Study
- 2012
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 58:1, s. 190-199
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:We evaluated the predictive ability of cystatin C and creatinine-based estimations of glomerular filtration rate (eGFR), including the Chronic Kidney Disease-Epidemiology (CKD-EPI) equation, in acute coronary syndrome (ACS) patients with (STE-ACS) or without (NSTE-ACS) ST elevation in a large contemporary ACS population.METHODS:Concentrations of cystatin C and creatinine, as well as eGFR at randomization, were measured in 16 401 patients in the Platelet Inhibition and Patient Outcomes (PLATO) study and evaluated as predictors of the composite end point of cardiovascular death or myocardial infarction within 1 year. Two Cox proportional hazards models were used, the first adjusting for clinical characteristics and the second for clinical characteristics plus the biomarkers N-terminal pro-B-type natriuretic peptide, troponin I, and C-reactive protein.RESULTS:The median cystatin C value was 0.83 mg/L. Increasing quartiles of cystatin C were strongly associated with poor outcome (6.9%, 7.1%, 9.5%, and 16.2%). The fully adjusted hazard ratios per SD of cystatin C in the NSTE-ACS and STE-ACS populations were 1.12 (95% CI 1.04-1.20) (n = 8053) and 1.06 (95% CI 0.97-1.17) (n = 5278), respectively. There was no significant relationship of cystatin C with type of ACS (STE or NSTE). c Statistics ranged from 0.6923 (cystatin C) to 0.6941 (CKD-EPI).CONCLUSIONS:Cystatin C concentration contributes independently in predicting the risk of cardiovascular death or myocardial infarction in NSTE-ACS, with no interaction by type of ACS. CKD-EPI exhibited the largest predictive value of all renal markers. Nevertheless, the additive predictive value of cystatin C or creatinine-based eGFR measures in the unselected ACS patient is small.
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