Inter-laboratory proficiency testing of the measurement of gypsum parameters with small numbers of participants

Conducting proficiency tests with large numbers of participants are not a problem because the ISO standard 13528:2015 describes many indicators that allow for proper assessment. However, there are proficiency testing (PT) schemes that involve only few participants. In such situations, the same difficulties exist for the selection of proper indicators and the criteria for assessing the participants' achievements. The Institute for Chemical Processing of Coal in Zabrze, Poland organised a round of PT of the determination of gypsum parameters. The results from six participants from Polish research entities and independent laboratories and methodology for the organisation this PT are presented. The performance evaluation criteria were determined using participants results due to the inability to use the metrologically valid procedure. The performance of the participants was evaluated using z′ and zeta scores.

Optimizing hepcidin measurement with a proficiency test framework and standardization improvement

ObjectivesHepcidin measurement advances insights in pathophysiology, diagnosis, and treatment of iron disorders, but requires analytically sound and standardized measurement procedures (MPs). Recent development of a two-level secondary reference material (sRM) for hepcidin assays allows worldwide standardization. However, no proficiency testing (PT) schemes to ensure external quality assurance (EQA) exist and the absence of a high calibrator in the sRM set precludes optimal standardization.MethodsWe developed a pilot PT together with the Dutch EQA organization Stichting Kwaliteitsbewaking Medische Laboratoriumdiagnostiek (SKML) that included 16 international hepcidin MPs. The design included 12 human serum samples that allowed us to evaluate accuracy, linearity, precision and standardization potential. We manufactured, value-assigned, and validated a high-level calibrator in a similar manner to the existing low- and middle-level sRM.ResultsThe pilot PT confirmed logistical feasibility of an annual scheme. Most MPs demonstrated linearity (R2>0.99) and precision (duplicate CV>12.2%), although the need for EQA was shown by large variability in accuracy. The high-level calibrator proved effective, reducing the inter-assay CV from 42.0% (unstandardized) to 14.0%, compared to 17.6% with the two-leveled set. The calibrator passed international homogeneity criteria and was assigned a value of 9.07 ± 0.24 nmol/L.ConclusionsWe established a framework for future PT to enable laboratory accreditation, which is essential to ensure quality of hepcidin measurement and its use in patient care. Additionally, we showed optimized standardization is possible by extending the current sRM with a third high calibrator, although international implementation of the sRM is a prerequisite for its success.

Selecting proficiency testing schemes and using its results in food testing

Proficiency testing (PT) is an objective tool to assess the laboratory’s performance. Participation in PT helps laboratories self-monitoring and self-evaluating the reliability of results. Nowadays, together with the development of laboratories, the demand of participating PT schemes is increasing, and there are variety of PT providers and PT schemes correspondingly. Hence, without of appropriate criteria for selection of PT schemes and the purposes of participating PT, time, money and effort could be excessively consumed, especially for laboratories that perform numerous different tests. In this study, principles for choosing appropriate PT schemes and using the PT results effectively for laboratories, particularly in food testing laboratories were provided.

PRINCIPAL COMPONENT ANALYSIS FOR SELECTION OF VARIABLES IN HOMOGENEITY AND STABILITY TESTS APPLIED TO PROFICIENCY TESTING SCHEMES

Proficiency Tests (PT) based on interlaboratory comparisons are activities aimed at assessing the technical competence of laboratories in carrying out specific measurements. The analyses of homogeneity and stability of prepared samples are an important step in ensuring the reliability of the comparison rounds, since improper selection of the parameter to carry out this evaluation can influence the promoted comparison. This paper proposes a method for selecting the most relevant variables aimed at improving homogeneity and stability tests in PT. For that matter, the approach relies on a variable importance index derived from Principal Components Analysis (PCA) parameters. The proposed method was applied to three different PT schemes (beverage, water and coal) in Brazil. Results indicate that the use of PCA was adequate to help the variable selection of homogeneity and stability tests in PT schemes. The selected subset of variables was corroborated by experts in the PT schemes analyzed.

Participation of Accredited Laboratories in Proficiency Testing Schemes and Interlaboratory Comparisons

This paper presents the elements of metrology laboratory accreditation for calibration in the scope of calibration E-05 Dimensions, and calibration for the subject: the distance and angle measures. During the accreditation, but also in its maintenance, calibration laboratories must prove their competence. Each laboratory must have the quality management procedures for monitoring the validity of the calibrations performed. This monitoring shall be planned and reviewed through: internal quality control, participation in the interlaboratory comparisons or proficiency testing schemes, repeated calibrations using the same or different methods, re-calibration of the saved samples and correlation of results for different characteristics of the sample. According to the ISO/IEC 17025:2005 standard, competence is proved by participating in interlaboratory comparisons or participation in Proficiency testing (PT) schemes. This paper aims to stimulate discussion and debate about ways of proving competence of calibration laboratories. We believe that, in the interpretation of ISO/IEC 17025, the laboratory can demonstrate competence by participating in any activity, PT schemes or interlaboratory comparisons, and they are equal to this need. The procedure and the results of the interlaboratory comparisons between two accredited laboratories will be described.

IUPAC/CITAC Guide: Selection and use of proficiency testing schemes for a limited number of participants—chemical analytical laboratories (IUPAC Technical Report)

A metrological background for implementation of proficiency testing (PT) schemes for a limited number of participating laboratories (fewer than 30) is discussed. Such schemes should be based on the use of certified reference materials (CRMs) with traceable property values to serve as PT items whose composition is unknown to the participants. It is shown that achieving quality of PT results in the framework of the concept “tested once, accepted everywhere” requires both metrological comparability and compatibility of these results. The possibility of assessing collective/group performance of PT participants by comparison of the PT consensus value (mean or median of the PT results) with the certified value of the test items is analyzed. Tabulated criteria for this assessment are proposed. Practical examples are described for illustration of the issues discussed.