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- Verwey, N A, et al.
(författare)
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A worldwide multicentre comparison of assays for cerebrospinal fluid biomarkers in Alzheimer's disease.
- 2009
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Ingår i: Annals of clinical biochemistry. - : SAGE Publications. - 0004-5632 .- 1758-1001. ; 46:Pt 3, s. 235-40
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Different cerebrospinal fluid (CSF) amyloid-beta 1-42 (Abeta(1-42)), total Tau (Tau) and Tau phosphorylated at threonine 181 (P-Tau) levels are reported, but currently there is a lack of quality control programmes. The aim of this study was to compare the measurements of these CSF biomarkers, between and within centres. METHODS: Three CSF-pool samples were distributed to 13 laboratories in 2004 and the same samples were again distributed to 18 laboratories in 2008. In 2004 six laboratories measured Abeta(1-42), Tau and P-Tau and seven laboratories measured one or two of these marker(s) by enzyme-linked immunosorbent assays (ELISAs). In 2008, 12 laboratories measured all three markers, three laboratories measured one or two marker(s) by ELISAs and three laboratories measured the markers by Luminex. RESULTS: In 2004, the ELISA intercentre coefficients of variance (interCV) were 31%, 21% and 13% for Abeta(1-42), Tau and P-Tau, respectively. These were 37%, 16% and 15%, respectively, in 2008. When we restricted the analysis to the Innotest (N = 13) for Abeta(1-42), lower interCV were calculated (22%). The centres that participated in both years (N = 9) showed interCVs of 21%, 15% and 9% and intra-centre coefficients (intraCV) of variance of 25%,18% and 7% in 2008. CONCLUSIONS: The highest variability was found for Abeta(1-42). The variabilities for Tau and P-Tau were lower in both years. The centres that participated in both years showed a high intraCV comparable to their interCV, indicating that there is not only a high variation between but also within centres. Besides a uniform standardization of (pre)analytical procedures, the same assay should be used to decrease the inter/intracentre variation.
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| 2. |
- Calcatelli, A., et al.
(författare)
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Results of the regional key comparison EUROMET.M.P-K1.a in the pressure range from 0.1 Pa to 1000 Pa
- 2005
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Ingår i: Metrologia. - 0026-1394 .- 1681-7575. ; 42:SUPPL.
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Tidskriftsartikel (refereegranskat)abstract
- Within EUROMET a regional key comparison (EUROMET.M.P-K1.a) was performed in order to compare national vacuum standards in the pressure range from 0.1 Pa to 1000 Pa. The participants were BNM-LNE (France), CEM (Spain), OMH (Hungary), IMGC-CNR (Italy), NPL (United Kingdom), MIKES (Finland), PTB (Germany), NMi (The Netherlands), SP (Sweden) and UME (Turkey). IMGC-CNR acted as pilot laboratory. The measurements were carried out from November 1998 to April 2002. The chosen pressure values (from 0.1 Pa to 1000 Pa) cover the most commonly required range for calibration in low-pressure applications. The transfer standards were commercially available capacitance diaphragm gauges (CDGs): one of them was prepared for the comparison by BNM-LNE (Fr) and two were prepared by IMGC-CNR (It). Two sensors had 133 Pa full scale (one absolute and one relative used as absolute) and one 1333 Pa full scale (absolute). For the two 133 Pa full scale sensors seven pressure steps were generated between 0.1 Pa and 100 Pa; for the 1333 Pa full scale sensor nine pressure steps were generated generally between 0.1 Pa and 1000 Pa. The uncertainty of the generated pressure was reported by each participant in the tables of the results that consisted in the generated pressure value, the uncertainty of the generated pressure, the reading of the gauge and the temperature of the standard at each target pressure. The pilot laboratory has analysed the results, after application of the correction for thermal transpiration, in terms of gauge factors for each gauge, and the combined uncertainty was evaluated by considering, besides the component due to the standards, taking into account the components due to the transfer standards to guarantee a uniform uncertainty analysis for all the participants. At each target pressure a EUROMET reference pressure was calculated; finally the difference between the pressures generated by each laboratory from the reference values was calculated and compared with its expanded uncertainty. The results of most of the laboratories showed a good agreement with the reference values. Only a few values of two laboratories were significantly off the reference values. From the available data a linkage to the CCM.P-K4 key comparison results from 1 Pa to 1000 Pa was possible by means of the results of three laboratories in the (1-30) Pa range and two for the (100-1000) Pa range who took part in both the comparisons. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the Mutual Recognition Arrangement (MRA).
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| 5. |
- Wang, Lei, et al.
(författare)
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Experimental investigation of flow fields in a square channel roughened with various ribs on one wall
- 2006
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Ingår i: American Society of Mechanical Engineers, Fluids Engineering Division FED. - 0888-8116. - 0791837904 - 0791847705
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Konferensbidrag (refereegranskat)abstract
- The present work studies the separated flow in a square channel with ribs on one wall by using the PIV method. In this study, the spacing between ribs is kept constant and the heights of rib are varied in order to investigate the influence of the pitch-to-height ratio, P/e on the flow structures. Depending on the various pitch ratios, the enclosure between ribs can be regarded as closed or open cavity. Results are included for mean velocity, streamlines, skin-friction coefficient, anisotropy parameter, turbulent kinetic energy production and two-point correlation. It is found that the separated shear layer in the closed cavity has strong momentum exchange with the mainstream. By contrast, the fluid contained in the open cavity is self-sustained and the outside streamlines are almost parallel to the bottom wall. Moreover, for the open cavity, the velocity fluctuations become vigorous as the flow reattaches directly on the trailing edge. Copyright
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| 7. |
- Visser, Pieter Jelle, et al.
(författare)
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Prevalence and prognostic value of CSF markers of Alzheimer's disease pathology in patients with subjective cognitive impairment or mild cognitive impairment in the DESCRIPA study: a prospective cohort study.
- 2009
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Ingår i: Lancet neurology. - : The Lancet Publishing Group. - 1474-4422 .- 1474-4465. ; 8:7, s. 619-27
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Alzheimer's disease (AD) pathology is common in patients with amnestic mild cognitive impairment (aMCI) without dementia, but the prevalence of AD pathology in patients with subjective cognitive impairment (SCI) and non-amnestic mild cognitive impairment (naMCI) is unknown. AD is characterised by decreased CSF concentrations of Abeta(42) and increased concentrations of tau. We investigated the prevalence of a CSF AD profile in patients with SCI, naMCI, or aMCI and the association of this profile with cognitive outcome in each group. METHODS: Patients with SCI, naMCI, aMCI, and neurologically healthy controls were recruited from 20 memory clinics across Europe, between January, 2003, and June, 2005, into this prospective cohort study. A CSF AD profile was defined as an abnormal ratio of Abeta(42):tau. Patients were assessed annually up to 3 years. Outcome measures were changes in memory, overall cognition, mini-mental state examination (MMSE) score, daily function, and progression to AD-type dementia. FINDINGS: The CSF AD profile was more common in patients with SCI (31 of 60 [52%]), naMCI (25 of 37 [68%]), and aMCI (56 of 71 [79%]) than in healthy controls (28 of 89 [31%]). The profile was associated with cognitive decline in patients with naMCI (memory, MMSE, and daily function) and in patients with aMCI (MMSE and daily function). In patients with aMCI, a CSF AD profile was predictive of AD-type dementia (OR 26.8, 95% CI 1.6-456.4). INTERPRETATION: AD is a common cause of SCI, naMCI, and aMCI and is associated with cognitive decline in patients with naMCI or aMCI. Patients with SCI might be in the early stages of AD, and cognitive decline might become apparent only after longer follow-up. FUNDING: European Commission; Ana Aslan International Foundation.
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