Chapter 3 - Measurement procedures

Towards the end of the year many of us have to summarise the activities and output of the past months and compare them with the original planning. Such an action stipulates also reflections about the effects of the performed work and the sustainability of achievements. Similar end-of-year thoughts are in the minds of editors of scientific journals. They are associated with a special challenge for the journal devoted to quality of measurement results as outlined in the following. Considering the huge amount of scientific journal articles, proceedings, institutional reports, PhD thesis, documentary standards, internet information, etc. published on measurement-related issues over an annual period, it seems to be timely to contemplate about the impact of the newly published measurement data, procedures and quality assurance (QA) tools. At first, what are the selection criteria used by many scientists for identifying a topic for research and later publication? It is certainly very welcome to select research topics of current relevance and importance. This corresponds with characteristics of ‘fashion’, namely to be popular. But who decides about such aspects? There are not only opinions from within the ‘scientific community’, which is anyway an ill-defined group, but also from research funding bodies, politicians, journalists, voters etc. Evaluations based on the number of scientific articles seem to indicate that contributions devoted to the topic of QA of measurements are still less ‘fashionable’ than reports about new analytical methods or data. The topic is therefore not well suited for ‘scientific headline hunting’, that means for attracting the attention of a wider scientific audience or even the public. Consequently, it is also less taken into account within generally executed mechanisms for research funding and selection procedures for career advancements. The additional characteristics of fashion, namely ‘shortterm appearance’ and ‘fast changing’ do not really fit with the design and application of appropriate QA measures or even QA systems. It requires not only time to develop and implement QA, but its effect and value will only become evident after longer periods of operation. Therefore, the fashion aspect is usually not a significant driver for performing and publishing QA-related work. On the other hand, if one uses the opportunity of the year’s end also to evaluate the number of really (possibly even widely) applied new measurement procedures in comparison to the number of published proposals in a given period of the recent past (such as the papers from 3 years ago), one may be disappointed by the impact of many research programmes and activities in analytical sciences. This puts in question the approach used in many selection and evaluation processes. In fact counting and comparing numbers of published papers or provided data is much easier than judging and comparing the quality of a project outcome. In that respect it is recognised that reliable, validated parameters for such impact-oriented comparisons are currently still mostly lacking. However, one can currently observe in several measurement areas an enhanced attention to QA. This is clearly demonstrated by the increasing number of accredited testing laboratories, proficiency providers and reference material producers. The stimulus comes mainly from regulations, such as accreditation demands on official product control laboratories, and competitive advantages in a globalising market. Therefore, QA of measurements is (a growing) characteristic of present and recent times. It is not antiquated or obsolete, that means it is ‘modern’. H. Emons (&) Geel, Belgium e-mail: JRC-IRMM-ACQUAL@ec.europa.eu

We undertook this study to evaluate method differences for 5 components analyzed by immunoassays, to explore whether the use of method-dependent reference intervals may compensate for method differences, and to investigate commutability of external quality assessment (EQA) materials. Twenty fresh native single serum samples, a fresh native serum pool, Nordic Federation of Clinical Chemistry Reference Serum X (serum X) (serum pool), and 2 EQA materials were sent to 38 laboratories for measurement of cobalamin, folate, ferritin, free T4, and thyroid-stimulating hormone (TSH) by 5 different measurement procedures [Roche Cobas (n = 15), Roche Modular (n = 4), Abbott Architect (n = 8), Beckman Coulter Unicel (n = 2), and Siemens ADVIA Centaur (n = 9)]. The target value for each component was calculated based on the mean of method means or measured by a reference measurement procedure (free T4). Quality specifications were based on biological variation. Local reference intervals were reported from all laboratories. Method differences that exceeded acceptable bias were found for all components except folate. Free T4 differences from the uncommonly used reference measurement procedure were large. Reference intervals differed between measurement procedures but also within 1 measurement procedure. The serum X material was commutable for all components and measurement procedures, whereas the EQA materials were noncommutable in 13 of 50 occasions (5 components, 5 methods, 2 EQA materials). The bias between the measurement procedures was unacceptably large in 4/5 tested components. Traceability to reference materials as claimed by the manufacturers did not lead to acceptable harmonization. Adjustment of reference intervals in accordance with method differences and use of commutable EQA samples are not implemented commonly.

This study attempts to prescribe hearing aid characteristics for one listening environment selected by an individual hearing aid user in order to provide better speech intelligibility than standard insertion gain prescriptions. The procedure is based on acoustic analyses of noise recorded by the user. The main purpose is to show the feasibility of the measurement and analysis procedure as a tool to investigate the consequences of the noise characteristics of everyday hearing aid use. The Speech Intelligibility Index (SII) is used as a criterion to optimize the insertion gain frequency response of the hearing aid. The results indicate that realistic background noise information is essential to achieve the best possible speech audibility. Maximizing the SII required higher insertion gain above 5000 Hz than assumed in conventional fitting procedures. Different insertion gain frequency responses are required for different listening conditions. The measurement procedure could identify acoustic listening conditions where hearing instruments would probably give no benefit.

Proficiency testing (PT), or external quality assessment (EQA), is intended to verify on a recurring basis that laboratory results conform to expectations for the quality required for patient care. Key factors for interpreting PT/EQA results are knowledge of the commutability of the samples used and the process used for target value assignment. A commutable PT/EQA sample demonstrates the same numeric relationship between different measurement procedures as that expected for patients' samples. Noncommutable PT/EQA samples frequently have a matrix-related bias of unknown magnitude that limits interpretation of results. PT/EQA results for commutable samples can be used to assess accuracy against a reference measurement procedure or a designated comparison method. In addition, the agreement of the results between different measurement procedures for commutable samples reflects that which would be seen for patients' samples. PT/EQA results for noncommutable samples must be compared to a peer group mean/median of results from participants who use measurement procedures that are expected to have the same or very similar matrix-related bias. Peer group evaluation is used to asses whether a laboratory is using a measurement procedure in conformance to the manufacturer's specifications and/or in conformance to other laboratories using the same technology. A noncommutable PT/EQA sample does not give meaningful information about the relationship of results for patients' samples between different measurement procedures. PT/EQA provides substantial value to the practice of laboratory medicine by assessing the performance of individual laboratories and, when commutable samples are used, the status of standardization or harmonization among different measurement procedures.

The present study was prompted by the ISO 15189 requirements that medical laboratories should estimate measurement uncertainty (MU). The method used to estimate MU included the: a) identification of quantitative tests, b) classification of tests in relation to their clinical purpose, and c) identification of criteria to estimate the different MU components. Imprecision was estimated using long-term internal quality control (IQC) results of the year 2016, while external quality assessment schemes (EQAs) results obtained in the period 2015-2016 were used to estimate bias and bias uncertainty. A total of 263 measurement procedures (MPs) were analyzed. On the basis of test purpose, in 51 MPs imprecision only was used to estimate MU; in the remaining MPs, the bias component was not estimable for 22 MPs because EQAs results did not provide reliable statistics. For a total of 28 MPs, two or more MU values were calculated on the basis of analyte concentration levels. Overall, results showed that uncertainty of bias is a minor factor contributing to MU, the bias component being the most relevant contributor to all the studied sample matrices. The model chosen for MU estimation allowed us to derive a standardized approach for bias calculation, with respect to the fitness-for-purpose of test results. Measurement uncertainty estimation could readily be implemented in medical laboratories as a useful tool in monitoring the analytical quality of test results since they are calculated using a combination of both the long-term imprecision IQC results and bias, on the basis of EQAs results.

A process is described to assess the commutability of a reference material (RM) intended for use as a calibrator, trueness control, or external quality assessment sample based on the difference in bias between an RM and clinical samples (CSs) measured using 2 different measurement procedures (MPs). This difference in bias is compared with a criterion based on a medically relevant difference between an RM and CS results to make a conclusion regarding commutability. When more than 2 MPs are included, the commutability is assessed pairwise for all combinations of 2 MPs. This approach allows the same criterion to be used for all combinations of MPs included in the assessment. The assessment is based on an error model that allows estimation of various random and systematic sources of error, including those from sample-specific effects of interfering substances. An advantage of this approach is that the difference in bias between an RM and the average bias of CSs at the concentration (i.e., amount of substance present or quantity value) of the RM is determined and its uncertainty estimated. An RM is considered fit for purpose for those MPs for which commutability is demonstrated.

Comparability of sample results and commutability of reference materials among different measurement procedures for protein C activity assays

Atmospheric turbulence is described in terms of a general formulation that does not assume any particular form for the turbulence structure function. The formulation allows for the possibility of Kolmogorov turbulence without bestowing any special favor to this type of turbulence. Expressions are obtained for the two-point correlation function of the complex amplitudes (i.e., Atmospheric MTF) and for the more general function, the two-point two-wavelength correlation function of the complex amplitudes. A cardinal set of measurement procedures naturally derives from these two functions that enables both the integrated strength and the average structure function of the turbulence in a propagation path to be characterized. Kolmogorov and non-Kolmogorov types of turbulence structure are measured impartially by these procedures. The measurement procedures are based on certain key properties of point-object images, properties that carry the essential information about the integrated effects of all mechanisms in the propagation path that affect the wavefronts. These mechanisms can include, but are not limited to, atmospheric turbulence, boundary layer turbulence, telescope aberrations, and the (corrective) effects of adaptive optics. The measurement procedures enable full end-to-end characterization of the entire propagation path between object and image. They take account of amplitude scintillation as well as phase variation in the wavefronts. Once the entire path has been characterized, certain wavelengths can be identified that lead to optimum image resolution. For HEL systems, optimum wavelengths lead to maximum irradiance at the target and maximum target lethality range. Large performance improvements are attained by use of optimum rather than non-optimum wavelengths.

The acoustic impact of ships has gained growing attention during the last few years. The Europe-an Union within the MSFD and associated TG Noise has assigned the anthropogenic noise from shipping as one of the contributors to a downgrading of the environmental status. The assessment and the corresponding mitigation measures would have to be proposed by 2016 and put in force by 2020. Therefore, it is vitally important for the ship industry and regulatory bodies to have available measurement procedures enabling the correct estimation of underwater noise radiated by vessels. Some international standard bodies such as ANSI and ISO have already developed and are still developing procedures for civil applications to quantify the underwater noise emission of ships. However, there are aspects of these procedures that are not yet consolidated from a technical point of view like the uncertainty associated to the procedure, and topics that are not yet addressed, like measurements in shallow waters. In this regard, the AQUO project, in the scope of the FP7 Europe-an Research Framework, set as one of its targets the development of a new European standard for underwater noise measurements adapted to both, shallow and deep waters with a special emphasis on the assessment of the uncertainties. This paper is a follow-up to the one previously written by TSI identifying the sources of uncertainties of the current measurement procedures. It will firstly present the measurement procedure resulting from the research done in the AQUO project. Thanks to the collaboration agreement signed by BV and TSI, this procedure has been largely adopted by Bureau Veritas in its new rule note (NR 614) titled Underwater Radiated Noise. Finally, the paper will also present the outcomes of the theoretical and experimental studies of its associated sources of deviation trying to provide realistic values for the uncertainty and repeatability of the measurement procedure. Due to its impact on marine life, the abatement of the Underwater Radiated Noise by ships has become the most out-standing novelty and difficult challenge that the Shipbuilding industry has ever faced. Therefore, the industry is trying to provide new solutions in order to comply with the new directives and requirements having been recently developed and promoted by the EU, Marine Institutions and the scientific community.

A measurement procedure for the rapid acquisition of U‐Pb dates for detrital zircons by quadrupole LA‐ICP‐MS was developed. The procedure achieves a threefold increase in measurement efficiency compared with the most commonly used methods. Utilising reduced background counting times and a shortened ablation period, a throughput of ~ 130 measurements/h can be achieved. The measurement procedure was characterised and validated using data from thirty‐nine sessions acquired over a twelve‐month period. Systematic measurement error in 206Pb/238U dates for reference materials used for quality control with ages between 28.2 and 2672 Ma was < 1.5%. Average measurement uncertainty, including both random and systematic components, was 1–4% (2s). Interrogation of time‐resolved calculated dates and signal intensities for each measurement allows for the detection and elimination of portions of measurements exhibiting age heterogeneities, zoning, lead loss and contamination by common lead. The measurement procedure diminishes the need to acquire cathodoluminescence imagery for routine detrital zircon applications further increasing throughput and reducing cost. The utility of the measurement procedure is demonstrated by the measurement of samples previously characterised by LA‐MC‐ICP‐MS.

As for most measurement procedures in the course of their development, measures of consciousness face the problem of coordination, that is, the problem of knowing whether a measurement procedure actually measures what it is intended to measure. I focus on the case of the Perceptual Awareness Scale to illustrate how ignoring this problem leads to ambiguous interpretations of subjective reports in consciousness science. In turn, I show that empirical results based on this measurement procedure might be systematically misinterpreted.

To help developing continuous improvement in Information and Communication Technology, new software are required with functionality and characteristics different from the traditional one. Thus, measurement procedures need to be tailored to this new computing context. In fact, the software functional size is one of the important cost drivers of software development projects. An accurate measurement needs a detailed definition of software requirements and may require an important measurement effort. However, this is not always available. Thus, well defined measurement procedures requiring little effort and providing approximate or rapid measurement results are needed. The COSMIC Functional Size Measurement (FSM) method has knew a great success compared to other methods since it addresses different types of software including business application, apps, etc. Moreover, it has been successfully used with UML diagrams for different objectives. In this paper, a Use Case based measurement procedure is proposed in order to estimate the functional size of mobile and web applications using COSMIC FSM method. The proposed procedure helps both beginners and experienced measurer in applying COSMIC and avoiding measurement errors. It is based on a set of measurement formulas tested and validated through the case study Restaurant Management System.

NHANES Monitoring of Serum 25-Hydroxyvitamin D: A Roundtable Summary1–3

Many individuals and laboratory teams, respectively, experience some kind of surprise when they are starting to compare their own measurement results with the ones from other laboratories. It could be a positive astonishment, namely how well the results are matching for a given measurand and sample. More often the contrary is observed and the origin of the discrepancies has to be identified. However, the potential of an interlaboratory comparison (ILC) including its evaluation depends strongly on the ILC design and the amount of information provided by the participants. This is not different from any other scientific study. But there are still several myths about the ‘do and don’t’ for ILCs. For instance, opinions such as ‘never combine measurement results from an ILC to assign a property value to a reference material’ or ‘increase the number of ILC participants for better approaching the true value’ are voiced at conferences or in committee meetings. Nevertheless, recent years have seen significant progress in the common understanding of underlying scientific principles and concepts of ILCs as well as in their design and execution. This was and continues to be driven by the needs to demonstrate the analytical capabilities (proficiency) of a set of laboratories, to identify the performance (limits) of a particular measurement method (actually a ‘measurement procedure’) or to characterize a specific property of the material under investigation. In the past, such judgments were left to some individuals or institutions, often based on a non-transparent division into ‘experts’ and ‘non-experts.’ It is interesting to note that the enhanced globalization of science, industry, trade, people’s mobility, communication, etc., has also put the traditional way of defining experts and competences in question — at least partially. Nowadays, it is usually not sufficient anymore to be identified by a well-known scientific ‘heavy weight’ or to belong to a traditionally well-reputed institution. One has regularly to provide evidence for the claimed competence. ILCs can be a relatively independent route for demonstrating specific competencies in measurement tasks. This is increasingly recognized also by regulators. For instance, official control laboratories for food or environmental monitoring in the European Union are required by legislation to successfully participate in dedicated ILCs. A prerequisite for the wider acceptance of ILC as a quality assurance tool was the combination of metrological principles for ILC designs with dedicated elements of standardization and internationally harmonized surveillance approaches via accreditation. This ranges from demanding participation in proficiency testing of laboratories which wish to obtain and keep an accreditation according to ISO/IEC 17025, to ensuring quality criteria for proficiency testing via application of ISO/IEC 17043. The latter document also contains a list of different goals which may be targeted by ILCs. In this respect, it is important to consider the interrelation between the three main components of a measurement exercise: the material (sample under investigation), the method(s) (measurement procedures used including all sample preparation and manipulation steps), and the laboratories participating. One cannot separately assess more than one of these components in the same ILC. For instance, in the framework of the characterization study of a new candidate reference material, the applied measurement methods have to be validated before applying them by laboratories of known (proven) competence. Measurement results obtained in such designed ILCs can be used for assigning property H. Emons (&) Geel, Belgium e-mail: JRC-IRMM-ACQUAL@ec.europa.eu

Precise calculation of total body surface area (TBSA) or premarked surface areas (P-MSAs) is of great importance in many biomedical applications. The aim of the paper was to present a simple procedure of measurement of P-MSAs in small animals and to determine a more accurate Meeh's constant (k), for a commonly used weight range of laboratory rats. A series of 30 Wistar rats, weighing 195-240 g, were anaesthetized and weighted. The TBSA of each animal was measured using a clear pocket and a planimeter. The data obtained were entered into the Meeh's formula (TBSA = kW(2/3)), the most commonly used for small experimental animals, so that a k value for each animal as well as a mean k value (9.83) were obtained. The TBSA of the animals was also calculated using the aforementioned mean k value and compared with that obtained using k values reported in previous studies. According to our findings, the new mean k value, determined with the use of our procedure of surface area measurement, ensured greater accuracy in the determination of the TBSA of experimental rats of a specific weight range. We also suggest a new procedure of surface area measurement which is easy, accurate and does not require animal sacrifice.