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| 23. |
- Nordenskjöld, Anna, 1977-, et al.
(författare)
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Short- and long-term individual variation in cardiac troponin in patients with stable coronary artery disease
- 2013
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Ingår i: Clinical Chemistry. - : American Association for Clinical Chemistry. - 0009-9147 .- 1530-8561. ; 59:2, s. 401-409
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: A rise or fall of cardiac troponin is a prerequisite for the diagnosis of acute myocardial infarction. Defining significant changes requires knowledge of both biological and analytical variation. The short-term biological variation of cardiac troponin in healthy individuals is 3%-48%. However, healthy individuals may not be representative for patients in whom cardiac troponin measurement is often of clinical importance. Therefore, we studied the individual variation of cardiac troponin in patients with symptoms of stable coronary artery disease.METHODS: Twenty-four patients scheduled for elective coronary angiography were included. Blood samples were drawn once at enrollment and serially at six 4-h intervals on the day before coronary angiography. Cardiac troponin was measured with hs-cTn assays from Abbott Laboratories (premarket cTnI assay) and Roche Diagnostics (Elecsys® cTnT assay with two different lots).RESULTS: The short-term individual variation in cardiac troponin I (cTnI) was 14%, the reference change value (RCV) 49%, and RCV-log-normal (rise/fall) 54%/-35%. The corresponding values for cTnT were 7%, 23%, and 26%/-21%. The long-term variation for cTnI was 24%, RCV 69%, and RCV-log-normal (rise/fall) 97%/-49%. The corresponding values for cTnT were 11%, 32%, and 37%/-27%.CONCLUSIONS: The short-term individual variation of cardiac troponin in patients with symptoms of stable coronary artery disease is similar to the biological variation previously demonstrated in healthy individuals. Our results suggest that a change in cardiac troponin concentrations of >50% can be used in attempting to diagnose acute myocardial injury. To detect significant long-term changes in cardiac troponin concentrations, larger changes will be required.
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| 24. |
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| 25. |
- Ristiniemi, Noora, et al.
(författare)
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Dry-Reagent Double-Monoclonal Assay for Cystatin C
- 2010
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 56:9, s. 1424-1431
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Cystatin C is a low molecular weight cysteine proteinase inhibitor whose plasma or serum concentrations have been shown to be better correlated with glomerular filtration rate than serum creatinine concentrations. Routine assays for cystatin C are based on use of polyclonal antibodies and immunoturbidimetric and nephelometric designs. This study aimed to develop a double-monoclonal immunoassay for cystatin C. METHODS: We tested functionality of 42 2-site antibody combinations involving 7 monoclonal antibodies with recombinant and plasma cystatin C. We developed a heterogeneous assay using 2 antibodies selected to give the best analytical performance. The assay used a dilution step and was based on a dry-reagent, all-in-one immunoassay concept with time-resolved fluorometry. The assay was performed on an automated immunoanalyzer in single wells that contained all the required assay components. We used heparin-derived plasma samples for methodological evaluation of the assay. RESULTS: From a relative epitope map involving 7 cystatin C-specific antibodies, we selected a pair of antibodies for a 2-site sandwich-type dry-reagent assay. Total assay time was 15 min, and 10 mu L of a 100-fold diluted sample was used. The analytical detection limit (background + 3SD) and functional detection limit (CV 20%) were 0.01 mg/L and 0.02 mg/L, respectively. Within-run and total assay imprecision were < 4.7% and < 5.6% (at 0.84-3.2 mg/L), respectively, and plasma recoveries of added cystatinCwere 94%-110%. Regression analysis with the Roche particle-enhanced immunoturbidimetric method yielded the following (SD): slope, 1.391 (0.029); y-intercept, - 0.152 (0.045) mg/L; S-y vertical bar x = 0.294 mg/L (n = 31). CONCLUSIONS: The developed assay enables rapid and reliable measurement of cystatin C. (C) 2010 American Association for Clinical Chemistry
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| 26. |
- Rosenling, Therese, et al.
(författare)
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The Impact of Delayed Storage on the Measured Proteome and Metabolome of Human Cerebrospinal Fluid
- 2011
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 57:12, s. 1703-1711
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Because cerebrospinal fluid (CSF) is in close contact with diseased areas in neurological disorders, it is an important source of material in the search for molecular biomarkers. However, sample handling for CSF collected from patients in a clinical setting might not always be adequate for use in proteomics and metabolomics studies. METHODS: We left CSF for 0, 30, and 120 min at room temperature immediately after sample collection and centrifugation/removal of cells. After tryptic digestion at 2 laboratories by nanoLC Orbitrap-MS and chipLC QTOF-MS, CSF proteomes were analyzed. Metabolome analysis was performed at 3 laboratories by NMR, GC-MS, and LC-MS. Targeted analyses of cystatin C and albumin were performed by LC-MS/MS in the selected reaction monitoring mode. RESULTS: We did not find significant changes in the measured proteome and metabolome of CSF stored at room temperature after centrifugation, except for 2 peptides and 1 metabolite, 2,3,4-trihydrobutanoic acid, of 5780 identified peptides and 93 identified metabolites. A sensitive protein stability marker, cystatin C, was not affected. CONCLUSIONS: The measured proteome and metabolome of centrifuged, human CSF is stable at room temperature for up to 2 hours. We cannot exclude, however, that changes undetectable with our current methodology, such as denaturation or proteolysis, might occur due to sample handling conditions. The stability we observed gives laboratory personnel at the collection site sufficient time to aliquot samples before freezing and storage at -80 °C.
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| 27. |
- Sacks, David B., et al.
(författare)
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Executive Summary: Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus
- 2011
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 57:6, s. 793-798
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- BACKGROUND: Multiple laboratory tests are used in the diagnosis and management of patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these assays varies substantially. APPROACH: An expert committee compiled evidence-based recommendations for the use of laboratory analysis in patients with diabetes. A new system was developed to grade the overall quality of the evidence and the strength of the recommendations. A draft of the guidelines was posted on the Internet, and the document was modified in response to comments. The guidelines were reviewed by the joint Evidence-Based Laboratory Medicine Committee of the AACC and the National Academy of Clinical Biochemistry and were accepted after revisions by the Professional Practice Committee and subsequent approval by the Executive Committee of the American Diabetes Association. CONTENT: In addition to the long-standing criteria based on measurement of venous plasma glucose, diabetes can be diagnosed by demonstrating increased hemoglobin A(1c) (Hb A(1c)) concentrations in the blood. Monitoring of glycemic control is performed by the patients measuring their own plasma or blood glucose with meters and by laboratory analysis of Hb A(1c). The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of autoantibodies, urine albumin, insulin, proinsulin, C-peptide, and other analytes are addressed. SUMMARY: The guidelines provide specific recommendations based on published data or derived from expert consensus. Several analytes are found to have minimal clinical value at the present time, and measurement of them is not recommended. (C) 2011 American Association for Clinical Chemistry and American Diabetes Association
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| 28. |
- Sacks, David B., et al.
(författare)
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Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus
- 2011
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 57:6, s. 1-47
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Multiple laboratory tests are used to diagnose and manage patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these tests varies substantially. APPROACH: An expert committee compiled evidence-based recommendations for the use of laboratory testing for patients with diabetes. A new system was developed to grade the overall quality of the evidence and the strength of the recommendations. Draft guidelines were posted on the Internet and presented at the 2007 Arnold O. Beckman Conference. The document was modified in response to oral and written comments, and a revised draft was posted in 2010 and again modified in response to written comments. The National Academy of Clinical Biochemistry and the Evidence Based Laboratory Medicine Committee of the AACC jointly reviewed the guidelines, which were accepted after revisions by the Professional Practice Committee and subsequently approved by the Executive Committee of the American Diabetes Association. CONTENT: In addition to long-standing criteria based on measurement of plasma glucose, diabetes can be diagnosed by demonstrating increased blood hemoglobin A(1c) (Hb A(1c)) concentrations. Monitoring of glycemic control is performed by self-monitoring of plasma or blood glucose with meters and by laboratory analysis of Hb A(1c). The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of autoantibodies, urine albumin, insulin, proinsulin, C-peptide, and other analytes are addressed. SUMMARY: The guidelines provide specific recommendations that are based on published data or derived from expert consensus. Several analytes have minimal clinical value at present, and their measurement is not recommended. (C) 2011 American Association for Clinical Chemistry and American Diabetes Association
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| 29. |
- Savukoski, Tanja, et al.
(författare)
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Troponin-Specific Autoantibody Interference in Different Cardiac Troponin I Assay Configurations
- 2012
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 58:6, s. 1040-1048
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Autoantibodies to cardiac troponins (cTnAAb) can interfere with the measurement of cardiac troponin I (cTnI) by immunoassays. The aim of this study was to explore the degree of cTnAAb interference in different cTnI assay configurations. METHODS: Ternary troponin complex was added into samples (serum or plasma, n = 132, 68% cTnAAb positive) from individuals without known cardiac conditions. The recovery of cTnI was then measured with 6 investigational cTnI assays (2, 3, or 4 antibodies per assay). Three of these assays were then selected for further comparison by use of samples (plasma, n = 210, 33% cTnAAb positive) from non-ST-elevation acute coronary syndrome patients in the FRISC-II (FRagmin/Fast Revascularisation during InStability in Coronary artery disease) cohort. Finally, these results were compared to those obtained with 3 commercial cTnI assays. RESULTS: Analytical recoveries varied widely among the 6 investigational assays. Notably the low recoveries (median 9%) of the midfragment-targeting reference assay were normalized (median 103%) with the use of the 4-antibody assay construct (3 capture, 1 tracer antibody) with only 1 antibody against a midfragment epitope. Reduced analytical recoveries correlated closely with measured autoantibody amounts. cTnI concentrations from cTnAAb-positive patient samples determined with 3 investigational assays confirmed the reduced concentrations expected from the low analytical recoveries. The results from the commercial cTnI assays with antibody selections representative for contemporary assay constructs revealed a similar underestimation (up to 20-fold) of cTnI in cTnAAb-positive samples. CONCLUSIONS: A novel cTnI assay deviating from the conventional IFCC-recommended midfragment approach substantially improves cTnI detection in samples containing cTnAAbs.
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| 30. |
- Shlipak, Michael G., et al.
(författare)
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Comparison of Cardiovascular Prognosis by 3 Serum Cystatin C Methods in the Heart and Soul Study
- 2011
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 57:5, s. 737-745
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Cystatin C is a promising new biomarker to estimate glomerular filtration (eGFR). However, the Siemens' cystatin C assay (Siemens), used in many longitudinal studies, has had limited clinical applicability because it requires a specific, dedicated instrument. Other companies, including Gentian and Roche, have developed cystatin C assays that can be used with most routine clinical chemistry analyzers. METHODS: We compared the agreement of Gentian and Roche with Siemens in 948 participants at the baseline visit of the Heart and Soul Study, a cohort of participants with established coronary artery disease who were followed for an average of 8 years. We then compared associations of all 3 cystatin C measures and eGFR-Modification of Diet in Renal Disease (MDRD) with clinical outcomes. RESULTS: The Gentian assay had higher correlation with Siemens (r = 0.96) than did Roche (r = 0.93, P < 0.001). After cross-tabulating quartiles of each cystatin C measure, agreements (κ statistic) were higher for Siemens and Gentian (0.73, 95% CI 0.72-0.75) than for Roche and Siemens (0.64, 0.63-0.66) or for Roche and Gentian (0.69, 0.65-0.71). These differences in agreement had minimal impact on associations with clinical outcomes; the hazard ratios (HRs) for mortality comparing the high vs low quartiles were 3.2 (95% CI 2.1-4.8) for Siemens, 3.1 (CI 2.1-4.7) for Gentian, 3.1 (CI 2.1-4.7) for Roche, and 1.6 (CI 1.1-2.3) for eGFR-MDRD, after multivariate adjustment. CONCLUSIONS: In summary, agreement with the Siemens' assay was modestly higher for the Gentian compared with the Roche assay, although all 3 methods for cystatin C measurement had similar utility as predictors of clinical outcomes.
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