References of "Accreditation and Quality Assurance"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailThe multivariate coefficient of variation for comparing serum protein electrophoresis techniques in External Quality Assessment schemes
Zhang, Lixin ULg; Albarède, Stéphanie; Dumont, Gilles et al

in Accreditation and Quality Assurance (2010)

External Quality Assessment (EQA) schemes are national or transnational programmes designed to control the analytical performance of clinical laboratories and to maintain inter-laboratory variability ... [more ▼]

External Quality Assessment (EQA) schemes are national or transnational programmes designed to control the analytical performance of clinical laboratories and to maintain inter-laboratory variability within acceptable limits. In such EQA programmes, participants are usually grouped by the type of assay technique/equipment they use. The coefficient of variation (CV) is a simple tool for comparing the inter-laboratory reproducibility of such techniques: the lower the CV, the better the analytical performance. Serum protein electrophoresis, a laboratory test profile consisting of five fractions (albumin, α1, α2, β and γ globulins) summing up to 100% of total proteins, can also be assayed in different ways depending on the media or the analytical principle. We propose a multivariate coefficient of variation for comparing the performance of electrophoretic techniques in EQA, thus extending the univariate CV concept. First, the compositional nature of electrophoretic data requires a one-to-one transformation from the 5-dimensional to the 4-dimensional space. Next, robust estimations of the mean and the covariance matrix are needed to avoid the effect of outliers. The new approach is illustrated on electrophoretic datasets from the French and Belgian national EQA programmes. [less ▲]

Detailed reference viewed: 176 (16 ULg)
Full Text
Peer Reviewed
See detailStatistical analysis of serum protein electrophoresis results in External Quality Assessment schemes
Zhang, Lixin ULg; Van Campenhout, Christel; Devleeschouwer, Nicole et al

in Accreditation and Quality Assurance (2008), 13(3), 149-155

The goal of External Quality Assessment (EQA) schemes is to ensure that results obtained on a particular specimen in a given clinical laboratory are compatible with those obtained by other laboratories on ... [more ▼]

The goal of External Quality Assessment (EQA) schemes is to ensure that results obtained on a particular specimen in a given clinical laboratory are compatible with those obtained by other laboratories on the same specimen. Serum protein electrophoresis is a laboratory test consisting of five fractions (albumin, a1, a2, b and c globulins), which sum up to 100% of total proteins. So far, in EQA schemes the five fractions have been analyzed separately as for ordinary tests like glucose or cholesterol. This approach does not consider the fractions as a whole and the linear relationship between them. A statistical approach has been developed to analyze EQA electrophoresis results from a global standpoint by using robust multivariate method to eliminate the effect of outlying profiles. As illustrated on electrophoretic data from the Belgian EQA scheme, the novel approach improves the detection of poor performing laboratories. The method will be implemented in the Belgian EQA scheme on a routine basis. [less ▲]

Detailed reference viewed: 108 (28 ULg)
Full Text
Peer Reviewed
See detailSetting up a decision rule from estimated uncertainty : emission limit value for PCDD and PCDF incineration plants in Wallonia, Belgium.
Bergmans, B.; Idczack, F.; Maetz, P. et al

in Accreditation and Quality Assurance (2008), 13

Complex analytical procedures are often required to prove the non-compliance with a specific legislation. In the case of a small overlap of the limit, integration of the method uncertainty in the decision ... [more ▼]

Complex analytical procedures are often required to prove the non-compliance with a specific legislation. In the case of a small overlap of the limit, integration of the method uncertainty in the decision-making process is essential. The decision rule proposed in Wallonia, Belgium, for the non-compliance of waste incineration plants with the EU limit value for PCDD and PCDF emissions is presented. The method uncertainty was estimated annually over 6 years from duplicate measurements using two top-down approaches. Depending on the congener, the standard uncertainty varies from 30 to 85%, with a good correlation between calculations. The analytical contribution was estimated using a bottom-up evaluation. The impact of the sampling step was deduced from the whole estimation and represents more than 80% of the total uncertainty budget. No optimisation is foreseen at this time because of practical field constraints. Based on the average fraction of each congener, the uncertainty associated with the measurement result has been established and shows a high stability over the years. Using this value, a guard band has been calculated and will be proposed to the regulatory body. [less ▲]

Detailed reference viewed: 41 (9 ULg)
Full Text
Peer Reviewed
See detailValidation of the analytical procedure for the determination of polyaromatic hydrocarbons in smoke flavourings using high performance liquid chromatography coupled to an ultraviolet, diode array or fluorescence detector
Brasseur, Catherine ULg; Brose, François ULg; Pirlot, Alain ULg et al

in Accreditation and Quality Assurance (2007), 12(10), 535-542

High performance liquid chromatography (HPLC) coupled to an ultraviolet (UV), diode array or fluorescence detector (UV/DAD/FLD) has been used to set up an analytical procedure for the quantification of 16 ... [more ▼]

High performance liquid chromatography (HPLC) coupled to an ultraviolet (UV), diode array or fluorescence detector (UV/DAD/FLD) has been used to set up an analytical procedure for the quantification of 16 EU priority polyaromatic hydrocarbons (PAHs) in smoke flavourings. The following parameters have been determined for the 16 EU priority PAHs: limit of detection, limit of quantification, precision (repeatability and intermediate precision), recovery and measurement uncertainty, using the concept of accuracy profiles. They were in close agreement with quality criteria described in the Commission Regulation (EC) no. 627/2006 concerning PAHs in smoke flavourings. [less ▲]

Detailed reference viewed: 123 (29 ULg)
Full Text
Peer Reviewed
See detailDioxin analysis in feed: cell-based assay versus mass spectrometry method
Scippo, Marie-Louise ULg; Rybertt, Soledad; Eppe, Gauthier ULg et al

in Accreditation and Quality Assurance (2006), 11(1-2), 38-43

In the determination of contaminants (dioxins, polychlorinated biphenyls, polyaromatic hydrocarbons), cell-based assays are useful methods for screening purposes: they are mainly characterized by high ... [more ▼]

In the determination of contaminants (dioxins, polychlorinated biphenyls, polyaromatic hydrocarbons), cell-based assays are useful methods for screening purposes: they are mainly characterized by high sample throughput and lower costs than the Mass Spectrometry (MS)-based methods. Although cell-based assays can be sensitive enough for the determination of dioxins and related substances in agreement with the presently tolerable limits in food and feed (Regulation No. 2375/2001/EC and Directive 2003/57/EC respectively), their lack of specificity make their use rather questionable in control laboratories. In this paper, we present and compare results obtained from the analysis of a limited number of feed samples by both gas chromatography-high resolution mass spectrometry (GC-HRMS) and cell-based assay (DR-CALUX: dioxin responsive-chemically activated luciferase gene expression) methods. The DR-CALUX screening led to less than 10% false non-compliant and no false compliant results. In addition, there is a good correlation between GC-HRMS and DR-CALUX data. However, these preliminary results have to be confirmed on a larger number of samples to demonstrate that total toxic equivalent (TEQ), including dioxins, furans and dioxin-like polychlorobiphenyls (PCBs) can be monitored in feed and food with a cell-based assay. [less ▲]

Detailed reference viewed: 108 (6 ULg)