Measurement validity measurements system

Six Sigma process improvement disciplines are typically organized around the acronym MAIC. The first step in a MA1C cycle is a Measure step, wherein one finds appropriate process responses to observe, identifies and validates measurement systems and collects baseline process performance (process monitoring) data. The second step is an Analyze step. This involves summarizing the initial... 

The UK Government has, for more than six years, funded the Valid Analytical Measurement (VAM) Programme, which is aimed at improving the quality and comparability of analytical measurements. The work undertaken within VAM is key to the underpinning of a modern physico-chemical and biochemical National Measurement System, By disseminating the activities of VAM across international boundaries and linking with other national measurement system VAM also aims to ensure the comparability of data worldwide. Thus VAM provides an infrastructure under which reliable measurements can be made for trade, regulation and health and safety provision. 

LGC has a strong interest in the quality of analytical measurements and played a lead role in the development of the UK s initiative on Valid Analytical Measurement (VAM). This is a programme supported by the UK government as part of the DTI programmes supporting the national measurement system. 

The preparation of this book was supported under contract with the Department of Trade and Industry (DTI) as part of the National Measurement System (NMS) Valid Analytical Measurement (VAM) Programme. The latter aims to improve the quality of analytical measurement in the UK. 

After five years as an analyst, Vicki moved within LGC to work on the DTI-funded Valid Analytical Measurement (VAM) programme. In this role, she was responsible for providing advice and developing guidance on method validation, measurement uncertainty and statistics. One of her key projects involved the development of approaches for evaluating the uncertainty in results obtained from chemical test methods. During this time, Vicki also became involved with the development and delivery of training courses on topics such as method validation, measurement uncertainty, quality systems and statistics for analytical chemists. 

Electrocardiograms and Cardiovascular Measurements. The availability of excellent GLP-validated telemetry systems has led to recent increases in the number of cardiovasular safety pharmacology studies conducted in primates. In addition, telemetry is now sometimes included as a design element in standard safety studies. Because of the ability to collect large amounts of high quality data over an extended time, total numbers of animals can often be reduced by appropriate application of... 

It is therefore essential to incorporate procedures that will ensure not only that the clinical data are collected in a uniform and similar manner at each investigating centre but that they are also handled and analysed in an identical manner. Measures such as the use of compatible validated computer systems and similar databases will allow the merging of data. At each centre, critical efficacy data should be determined with identical procedures and, where appropriate, these should be specified in protocols... 

Each tested output is activated or deactivated a few times to visualize clearly the transmission. The visualization of the transmitted signals is made either on the activated system itself (mechanical indicators of electrovalves, start of motors or pumps) or by using an adequate validation measuring equipment. 

FIGURE 2 Role of method validation in quality of analytical measurements. Validation is the process to demonstrate the fitness for purpose of the analytical system [4,8,14,15]. 

If there is any doubt about whether 100% of the analyte is presented to the measuring system or that the response of the calibrated system leads to no bias, then the assumptions must be tested during method validation and appropriate actions taken. If a series of measurements of a CRM (not used for calibration) leads to the conclusion that there is significant bias in the observed measurement result, the result should be corrected, and the measurement uncertainty should include the uncertainty of the measurement of the bias. If the bias is considered insignificant, no correction need be made, but measuring the bias and concluding that it is zero adds uncertainty (perhaps the bias was not really zero but is less than the uncertainty of its measurement). One approach to measurement uncertainty is therefore to include CRMs in the batch to be used to correct for bias, and then the uncertainty of estimation of bias, which includes the uncertainty of the quantity value of the CRM, is combined with the within-laboratory reproducibility. In some fields of analysis it is held that routine measurement and correction for bias... 

Photolysis of oxalate complexes show that there is a strong tendency to undergo photoredox decompositions, resulting in oxides of carbon. Two useful applications of this are (i) the system based on the redox photolysis of aqueous [Fe(C204)3]3- is widely used for chemical actinometry 100 and (ii) UV irradiation of (phos)2M(C204) complexes (M = Pd, Pt) result in loss of two molecules of carbon dioxide and production of the synthetically useful, coordinatively unsaturated M° complex (phos)2M.19 One reaction which, if generally applicable to dicarboxylate complexes, may have considerable impact upon the validity of physical measurements upon these systems is the rather unusual, room temperature, solid-state reaction (2).102... 

Use of portable emissions measurement systems (PEMS) for validation and development of passenger car emission factors. 18th International Symposium Transport and Air Pollution. May 18-19, 2010, Duebendorf, Switzerland... 

When one builds a quantitative model using PCR or PLS, one is often not aware that the model parameters that are generated present an opportunity to learn some useful information. Information extracted from these model parameters cannot only be used to better understand the process and measurement system, but also lead to improved confidence in the validity of the quantitative method itself. 

To encompass the seemingly incompatible qualitative and quantitative components of total error, we evaluate them under the umbrella of so-called data quality indicators (DQIs). DQIs are a group of quantitative and qualitative descriptors, namely precision, accuracy, representativeness, comparability, and completeness, summarily referred to as the PARCC parameters, used in interpreting the degree of acceptability or usability of data (EPA, 1997a). As descriptors of the overall environmental measurement system, which includes field and laboratory measurements and processes, the PARCC parameters enable us to determine the validity of the collected data. 

Completeness—A measure of the amount of valid data obtained from a measurement system compared to the amount that was expected to be obtained under correct, normal conditions. 

The term chemical measurement can cover all these determinations, including identification [6], Identification defines the so called analyte by means of chemical, electrochemical, spectroscopical and other physical properties. In most cases identification is done by measurements. Identification is valid only in a reference system. The terms describing the analytical problem (see Fig. 4), the measuring system used, the reference methods and the reference materials, belong together as the reference system. 

In chemical analysis the difference in response the measurement system to a reference material standard of the sample can be very large, indeed in many cases it can be impossible to evaluate. To overcome this standard methods are developed and validated, often by means of collaborative studies and in many cases the... 

The chemist s eyeballing a graduated dropping funnel to deliver reactants at desired feed rates into a glass reactor, or setting up precise delivery using a validated peristaltic pump, is generally replaced by quite different flow measurement systems in the pilot plant and plant worlds. 

For smaller laboratories, the work involved in validation is often difficult, but there are two alternatives. Users can choose a system with an existing standardized and validated protocol and validated interpretation system. Commercially available kits generally provide these, and when utilized exactly as described in the kit insert, are guaranteed to provide diagnostically useful results. A second option would be to use one of the more common standard systems of fixatives with known antibodies, in which publication data has provided some evidence of functionality. As an example, a laboratory could use a 10% neutral buffered formalin fixation with a standard protocol, followed by a biotin-streptavidin HRP system, using a monoclonal antibody combination called AE1/AE3. This has been proven to be a reliable measure of cytokeratin in tissue sections. 

Before assessing the other validation parameters (trueness, recovery, precision, selectivity, specificity, detection capability, stability, and applicability/mgged-ness), the appropriateness of the calibration model should be evaluated. The correctness of the analytical determination of elements in food and food products depends indeed on the choice and the evaluation of the calibration model. The calibration model gives the mathematical relationship between the signal of the measuring system and the concentration in the sample. Several authors have published guidelines concerning calibration in analytical chemistry [5-7]. 

Generally, the analysis of environmental pollutants is considered as a necessary expense that is performed solely if stated by law. With less expensive screening methods and automated modern equipment to analyze suspect samples, the cost of analysis will become much lower. Hence, the attitude towards QA would most probably be more positive and the analytical work much more reliable for the customers. This also strengthens the international competitiveness of European producers. The credibility of the entire monitoring chain (screening methods, reference and standardized methods, as well as CRMs for the quality control of these methods) lies in the adequacy and integration of all three levels of the system. The adequate development and validation of methods is a prerequisite for a harmonized measurement system [80]. 

We are grateful for financial support from the Department of Trade and Industry as part of the National Measurement System Valid Analytical Measurement programme. 

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