| 1. |
- Bjerke, Maria, 1977, et al.
(författare)
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Assessing the commutability of reference material formats for the harmonization of amyloid beta measurements.
- 2016
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Ingår i: Clinical chemistry and laboratory medicine : CCLM / FESCC. - : Walter de Gruyter GmbH. - 1437-4331 .- 1434-6621. ; 54:7, s. 1177-91
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The cerebrospinal fluid (CSF) amyloid-β (Aβ42) peptide is an important biomarker for Alzheimer's disease (AD). Variability in measured Aβ42 concentrations at different laboratories may be overcome by standardization and establishing traceability to a reference system. Candidate certified reference materials (CRMs) are validated herein for this purpose. METHODS: Commutability of 16 candidate CRM formats was assessed across five CSF Aβ42 immunoassays and one mass spectrometry (MS) method in a set of 48 individual clinical CSF samples. Promising candidate CRM formats (neat CSF and CSF spiked with Aβ42) were identified and subjected to validation across eight (Elecsys, EUROIMMUN, IBL, INNO-BIA AlzBio3, INNOTEST, MSD, Simoa, and Saladax) immunoassays and the MS method in 32 individual CSF samples. Commutability was evaluated by Passing-Bablok regression and the candidate CRM termed commutable when found within the prediction interval (PI). The relative distance to the regression line was assessed. RESULTS: The neat CSF candidate CRM format was commutable for almost all method comparisons, except for the Simoa/MSD, Simoa/MS and MS/IBL where it was found just outside the 95% PI. However, the neat CSF was found within 5% relative distance to the regression line for MS/IBL, between 5% and 10% for Simoa/MS and between 10% and 15% for Simoa/MSD comparisons. CONCLUSIONS: The neat CSF candidate CRM format was commutable for 33 of 36 method comparisons, only one comparison more than expected given the 95% PI acceptance limit. We conclude that the neat CSF candidate CRM can be used for value assignment of the kit calibrators for the different Aβ42 methods.
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| 2. |
- Grubb, Anders, et al.
(författare)
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First certified reference material for cystatin C in human serum ERM-DA471/IFCC.
- 2010
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Ingår i: Clinical Chemistry and Laboratory Medicine. - 1434-6621. ; 48:11, s. 1619-1621
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Tidskriftsartikel (refereegranskat)abstract
- The IFCC Working Group for the Standardisation of Cystatin C (WG-SCC), in collaboration with the Institute for Reference Materials and Measurements (IRMM), announces the availability of the new certified reference material ERM-DA471/IFCC. The material was characterised using a pure protein primary reference preparation (PRP) as calibrant. The PRP was prepared from recombinant cystatin C, and its concentration measured using dry mass determination. The characterisation of ERM-DA471/IFCC was performed by particle enhanced immuno-nephelometry, particle enhanced immuno-turbidimetry, and enzyme amplified single radial immuno-diffusion. The certified cystatin C mass concentration in ERM-DA471/IFCC, if reconstituted according to the specified procedure, is 5.48 mg/L, the expanded uncertainty (k=2) being 0.15 mg/L.
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| 3. |
- Grubb, Anders, et al.
(författare)
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Generation of a new cystatin C-based estimating equation for glomerular filtration rate by use of 7 assays standardized to the international calibrator
- 2014
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 60:7, s. 974-986
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Many different cystatin C-based equations exist for estimating glomerular filtration rate. Major reasons for this are the previous lack of an international cystatin C calibrator and the nonequivalence of results from different cystatin C assays.METHODS:Use of the recently introduced certified reference material, ERM-DA471/IFCC, and further work to achieve high agreement and equivalence of 7 commercially available cystatin C assays allowed a substantial decrease of the CV of the assays, as defined by their performance in an external quality assessment for clinical laboratory investigations. By use of 2 of these assays and a population of 4690 subjects, with large subpopulations of children and Asian and Caucasian adults, with their GFR determined by either renal or plasma inulin clearance or plasma iohexol clearance, we attempted to produce a virtually assay-independent simple cystatin C-based equation for estimation of GFR.RESULTS:We developed a simple cystatin C-based equation for estimation of GFR comprising only 2 variables, cystatin C concentration and age. No terms for race and sex are required for optimal diagnostic performance. The equation, [Formula: see text] is also biologically oriented, with 1 term for the theoretical renal clearance of small molecules and 1 constant for extrarenal clearance of cystatin C.CONCLUSIONS:A virtually assay-independent simple cystatin C-based and biologically oriented equation for estimation of GFR, without terms for sex and race, was produced.
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| 4. |
- Kuhlmann, Julia, et al.
(författare)
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CSF Aβ1-42 - an excellent but complicated Alzheimer's biomarker - a route to standardisation.
- 2017
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Ingår i: Clinica chimica acta; international journal of clinical chemistry. - : Elsevier BV. - 1873-3492. ; 467, s. 27-33
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Tidskriftsartikel (refereegranskat)abstract
- The 42 amino acid form of amyloid β (Aβ1-42) in cerebrospinal fluid (CSF) has been widely accepted as a central biomarker for Alzheimer's disease. Several immunoassays for CSF Aβ1-42 are commercially available, but can suffer from between laboratory and batch-to-batch variability as well as lack of standardisation across assays. As a consequence, no general cut-off values have been established for a specific context of use (e.g., clinical diagnostics) and selection of individuals for enrolment in clinical trials (patient stratification) remains challenging. The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) has initiated a working group for CSF proteins (WG-CSF) to facilitate standardisation of CSF Aβ1-42 measurement results. The efforts of the IFCC WG-CSF include the development of certified reference materials (CRMs) and reference measurement procedures (RMPs) for key biomarkers. Two candidate RMPs for quantification of Aβ1-42 in CSF based on liquid chromatography tandem mass spectrometry have been developed and tested in two ring trials. Furthermore, two commutability studies including native CSF pools, artificial CSF and spiked materials have been completed. On the basis of these studies, human CSF pools containing only endogenous Aβ1-42 at three concentrations were selected as the format for future CRMs that are now being processed.
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| 5. |
- Mattsson, Niklas, 1979, et al.
(författare)
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Proficiency testing programs for Alzheimer's disease cerebrospinal fluid biomarkers.
- 2012
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Ingår i: Biomarkers in medicine. - : Future Medicine Ltd. - 1752-0371 .- 1752-0363. ; 6:4, s. 401-7
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Tidskriftsartikel (refereegranskat)abstract
- Cerebrospinal fluid (CSF) biomarkers are increasingly used for diagnosis of Alzheimer's disease in research, clinical trials and clinical settings. As for other biochemical measurements, variability between laboratories for these biomarkers may be monitored by proficiency testing programs, where participating laboratories use their local routine methods to analyze test samples shipped from a central laboratory. In this review, we summarize the results from the last years' pilot proficiency programs and describe the ongoing standardization efforts in this area. Global proficiency testing for CSF biomarkers is now fully established. It will continue to play an important part in the standardization of measurements that is a prerequisite for the broad-scale future implementation of CSF biomarkers.
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| 6. |
- Mattsson, Niklas, 1979, et al.
(författare)
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Reference measurement procedures for Alzheimer's disease cerebrospinal fluid biomarkers: definitions and approaches with focus on amyloid β42.
- 2012
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Ingår i: Biomarkers in medicine. - : Future Medicine Ltd. - 1752-0371 .- 1752-0363. ; 6:4, s. 409-17
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Tidskriftsartikel (refereegranskat)abstract
- Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) are increasingly used in clinical settings, research and drug trials. However, their broad-scale use on different technology platforms is hampered by the lack of standardization at the level of sample handling, determination of concentrations of analytes and the absence of well-defined performance criteria for in vitro diagnostic or companion diagnostic assays, which influences the apparent concentration of the analytes measured and the subsequent interpretation of the data. There is a need for harmonization of CSF AD biomarker assays that can reliably, across centers, quantitate CSF biomarkers with high analytical precision, selectivity and stability over long time periods. In this position paper, we discuss reference procedures for the measurement of CSF AD biomarkers, especially amyloid β42 and tau. We describe possible technical approaches, focusing on a selected reaction monitoring mass spectrometry assay as a candidate reference method for quantification of CSF amyloid β42.
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| 7. |
- Merlini, Giampaolo, et al.
(författare)
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Standardizing plasma protein measurements worldwide: a challenging enterprise
- 2010
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Ingår i: Clinical Chemistry and Laboratory Medicine. - 1434-6621. ; 48:11, s. 1567-1575
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Forskningsöversikt (refereegranskat)abstract
- The need for harmonizing laboratory results is particularly intense in the field of quantitative protein assays in consideration of the clinical impact of specific protein measurements and their relevance in monitoring disease. We report the efforts made by the Committee on Plasma Proteins of the IFCC Scientific Division to achieve worldwide comparability in plasma protein results. We focus on the production of reference materials and the methods applied throughout their production process. Particularly, the recent characterization of ERM-DA470k/IFCC and ERM-DA472/IFCC has demonstrated that it is possible to reproduce the earlier established procedures and thereby maintain standardization. Plasma protein reference materials have had a substantial impact in improving the harmonization of patient protein results that should translate into better patient care. Clin Chem Lab Med 2010;48:1567-75.
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| 8. |
- Pannee, Josef, et al.
(författare)
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A Selected Reaction Monitoring (SRM)-Based Method for Absolute Quantification of A beta(38), A beta(40), and A beta(42) in Cerebrospinal Fluid of Alzheimer's Disease Patients and Healthy Controls
- 2013
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Ingår i: Journal of Alzheimer's Disease. - 1387-2877. ; 33:4, s. 1021-1032
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Tidskriftsartikel (refereegranskat)abstract
- Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) are increasingly used in research centers, clinical trials, and clinical settings. However, their broad-scale use is hampered by lack of standardization across analytical platforms and by interference from binding of amyloid-beta(A beta) to matrix proteins as well as self-aggregation. Here, we report on a matrix effect-resistant method for the measurement of the AD-associated 42 amino acid species of A beta(A beta(42)), together with A beta(40) and A beta(38) in human CSF based on mass spectrometric quantification using selected reaction monitoring (SRM). Samples were prepared by solid-phase extraction and quantification was performed using stable-isotope labeled A beta peptides as internal standards. The diagnostic performance of the method was evaluated on two independent clinical materials with research volunteers who were cognitively normal and AD patients with mild to moderate dementia. Analytical characteristics of the method include a lower limit of quantification of 62.5 pg/mL for A beta(42) and coefficients of variations below 10%. In a pilot study on AD patients and controls, we verified disease-association with decreased levels of A beta(42) similar to that obtained by ELISA and even better separation was obtained using the A beta(42)/A beta(40) ratio. The developed assay is sensitive and is not influenced by matrix effects, enabling absolute quantification of A beta(42), A beta(40), and A beta(38) in CSF, while it retains the ability to distinguish AD patients from controls. We suggest this SRM-based method for A beta peptide quantification in human CSF valuable for clinical research and trials.
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| 9. |
- Pannee, Josef, 1979, et al.
(författare)
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A selected reaction monitoring (SRM)-based method for absolute quantification of Aβ38, Aβ40, and Aβ42 in cerebrospinal fluid of Alzheimer's Disease patients and healthy controls.
- 2013
-
Ingår i: Journal of Alzheimer's Disease. - 1387-2877. ; 33:4, s. 1021-32
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Tidskriftsartikel (refereegranskat)abstract
- Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) are increasingly used in research centers, clinical trials, and clinical settings. However, their broad-scale use is hampered by lack of standardization across analytical platforms and by interference from binding of amyloid-β (Aβ) to matrix proteins as well as self-aggregation. Here, we report on a matrix effect-resistant method for the measurement of the AD-associated 42 amino acid species of Aβ (Aβ42), together with Aβ40 and Aβ38 in human CSF based on mass spectrometric quantification using selected reaction monitoring (SRM). Samples were prepared by solid-phase extraction and quantification was performed using stable-isotope labeled Aβ peptides as internal standards. The diagnostic performance of the method was evaluated on two independent clinical materials with research volunteers who were cognitively normal and AD patients with mild to moderate dementia. Analytical characteristics of the method include a lower limit of quantification of 62.5 pg/mL for Aβ42 and coefficients of variations below 10%. In a pilot study on AD patients and controls, we verified disease-association with decreased levels of Aβ42 similar to that obtained by ELISA and even better separation was obtained using the Aβ42/Aβ40 ratio. The developed assay is sensitive and is not influenced by matrix effects, enabling absolute quantification of Aβ42, Aβ40, and Aβ38 in CSF, while it retains the ability to distinguish AD patients from controls. We suggest this SRM-based method for Aβ peptide quantification in human CSF valuable for clinical research and trials.
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| 10. |
- Pannee, Josef, 1979, et al.
(författare)
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Round robin test on quantification of amyloid-β 1-42 in cerebrospinal fluid by mass spectrometry.
- 2016
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Ingår i: Alzheimer's & dementia : the journal of the Alzheimer's Association. - : Wiley. - 1552-5279. ; 12:1, s. 55-59
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Tidskriftsartikel (refereegranskat)abstract
- Cerebrospinal fluid (CSF) amyloid-β 1-42 (Aβ42) is an important biomarker for Alzheimer's disease, both in diagnostics and to monitor disease-modifying therapies. However, there is a great need for standardization of methods used for quantification. To overcome problems associated with immunoassays, liquid chromatography-tandem mass spectrometry (LC-MS/MS) has emerged as a critical orthogonal alternative.
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