Accreditation and Quality Assurance (v.15, #10)
‘Fitness-for-intended-use’ is an important concept in measurement by Paul De Bièvre (545-546).
Joint parameter confidence regions improve the power of parametric regression in method-comparison studies by W. A. Sadler (547-554).
Paired data from medical laboratory method-comparison experiments are commonly analysed by parametric linear regression, and differences from the line of identity are invariably assessed by determining whether confidence intervals for slope (b) and intercept (a) enclose 1 and 0, respectively. However, it has been shown that such analyses have low statistical power when the data maximum to minimum range ratio is small (maximum to minimum ratio of X values ≤ 2–1). Sample sizes > 500 are typically required to give a worthwhile probability of detecting clinically meaningful method biases. An alternative significance test is considered here, based on whether the elliptically shaped area representing the joint slope and intercept confidence region encloses the point [b = 1, a = 0]. Simulations showed a clear range related pattern. Relative to confidence intervals, the joint parameter confidence ellipse is associated with small reductions in power when the data range ratio is very large (several thousand-fold), but this is more than compensated by spectacular improvements in power with small range ratios. Sample size reductions were typically >20-fold for a 2–1 range ratio. Worthwhile sample size reductions are possible for all but the largest range ratios and in the particular case of the narrow physiological ranges associated with a number of medical laboratory tests (or their equivalents in other measurement contexts), the reductions could convert sample size requirements from impossibly large to eminently manageable. A Win32 computer program is provided, which converts data range, uncertainty characteristics and user-defined power settings into estimates of minimum sample size.
Keywords: Parametric regression; Deming regression; Errors-in-variables regression; Statistical power; Confidence interval; Confidence region
Rapid method for determination of protein content in cereals and oilseeds: validation, measurement uncertainty and comparison with the Kjeldahl method by Bojana Beljkaš; Jovana Matić; Ivan Milovanović; Pavle Jovanov; Aleksandra Mišan; Ljubiša Šarić (555-561).
The objective of this research was to test suitability of the Dumas combustion method to completely substitute the Kjeldahl method in routine laboratory determination of crude protein content in cereals and oilseeds. The validation of the method demonstrated that it is able to determine crude protein content in cereals and oilseeds in an efficient and accurate manner, with a detection limit w(N) = 0.006%, quantification limit w(N) = 0.019%, repeatability precision RSD r = 0.41%, intra-laboratory reproducibility precision RSD R = 0.74%, trueness, expressed in terms of bias b = 0.43%, and linear response between (2.36–19.2) mg N. Measurement uncertainty, expressed as relative expanded uncertainty (coverage factor k = 2, confidence level 95%), was calculated from validation data (U rel = 2.24%). In order to examine the relationship between two methods, 15 cereal grain and oilseed samples were analyzed using Dumas and Kjeldahl procedure. The Kjeldahl procedure gave slightly lower w(N) values than the Dumas procedure: w K(N) = 0.9905 w D(N) = 0.0376 (R 2 = 0.9996). Relative standard deviations and results of homogeneity test obtained during analysis of complex cereal products (cereal breakfast and muesli bars) show that the Dumas combustion method may be less suitable for analysis of such samples compared to Kjeldahl method.
Keywords: Dumas method; Kjeldahl method; Cereals; Oilseeds; Validation; Measurement uncertainty
Preparation and certification of a fish oil natural matrix reference material for organochlorine pesticides by Adel B. Shehata; Ibrahim F. Tahoun (563-568).
The mass fractions of six organochlorine pesticides in a fish oil certified reference material (CRM) have been determined using multiple methods of analysis. Fish oil was extracted from the filet of Tilapia fish collected from the River Nile, and this CRM was recently issued by the National Institute of Standards (NIS). It can be used as natural matrix CRM for organochlorine pesticides determination in fish and for marine environmental measurement purposes. The analytical methods used are described, and the obtained results were combined to calculate the mass fractions of the six detected organochlorine pesticides and their associated uncertainty values. It has been concluded that mass fractions of four pesticides are certified values. These are 1,1-(dichloroethylidene)bis[4-chlorobenzene](4,4′-DDE), 1,1-(2,2,-dichloroethylidene)bis[4-chlorobenzene] (4,4′-DDD), 1-chloro-2-[2,2,2-trichloro-1-(4-chlorophenyl)ethyl]benzene (2,4′-DDT) and 1,1-(2,2,2-trichloroethylidene)bis[4-chlorobenzene] (4,4′-DDT). Meanwhile, mass fractions of two pesticides were reference values. These are heptachlor and 1-chloro-2-[2,2-dichloro-1-(4-chlorophenyl)ethyl]benzene (2,4′-DDD).
Keywords: Fish oil; Pesticides; Homogeneity; GC; Combining data
How prepared are medical and non-medical laboratories in Jamaica for accreditation? by Donovan McGrowder; Tazhmoye Crawford; Rachael Irving; Paul Brown; Lennox Anderson-Jackson (569-577).
Laboratory accreditation is becoming increasingly accepted around the world as a means of identifying technically competent laboratories. The purpose of this research was to examine the level of preparedness of medical and non-medical laboratories for accreditation and investigate the challenges experienced by these laboratories in preparing for accreditation. A cross-sectional descriptive survey using close-ended, 28-item(4 pages), self-administered questionnaire that captured management and technical information such as documentation, quality control aspects of ISO 15189:2007 and ISO 17025:2005 standards was carried out. The sample consisted of 29 laboratories: medical, 55.2% and non-medical, 44.8%. Eleven percent of the laboratories indicated that they would be applying for accreditation in less than 3 months. Approximately one-sixth (16.7%) of non-medical laboratories were between 90 and 100% prepared for accreditation compared to 6.3% of medical laboratories. Barriers to accreditation were cost, 72.4%; lack of motivation of staff, 34.5%; unclear requirements and challenges with the interpretation and implementation of ISO 15189:2007 and ISO 17025:2005 standards, 31.0%; lack of support from management, 24.1%; and absence of a quality manager, 20.7%. Laboratories that employed quality managers had a greater preparation for accreditation index (34.1 ± 7.7) compared to those who did not employ a quality manager (28.0 ± 2.5, PAI t-test = −3.085, P = 0.006). The preparation for accreditation of most of the laboratories in Jamaica is at a satisfactory level. The barriers to accreditation highlight the need for a collective effort of management, technical staff and all stakeholders in addressing these issues to ensure that these laboratories are accredited.
Keywords: Medical; Non-medical; Laboratories; Jamaica; Accreditation
Erratum to: How prepared are medical and non-medical laboratories in Jamaica for accreditation? by Donovan McGrowder; Tazhmoye Crawford; Rachael Irving; Paul Brown; Lennox Anderson-Jackson; Paul Bourne (579-579).
Remembering the Stockholm Consensus by Xavier Fuentes-Arderiu (581-584).
Last year marked the tenth anniversary of the conference Strategies to Set Global Quality Specifications in Laboratory Medicine, which was held in Stockholm. The main outcome of this conference was a hierarchy of models to set metrological requirements, commonly known as the Stockholm Consensus. Belief in the appropriateness and scientific rigour of this Consensus has since been disseminated around the world. The Stockholm Consensus has made the biological variation model the model that is most commonly used to set metrological requirements. However, this model is not objective, because it is based on the selection of the one of three multiplication factors that reflects the mean biological variation. In addition to this lack of objectivity and other weaknesses of the biological variation model, the so-called Stockholm Consensus was not a true consensus process. Since our knowledge of this field continues to grow, the setting of metrological requirements should be a matter of true consensus based on the state of the art, rather than a “pseudo-objective” process. Metrological requirements should ensure that clinical laboratories do not produce measurement results that are less precise than their measuring systems allow.
Keywords: Metrological requirements; Consensus process; Analytical goals; Analytical specifications; Analytical performance; Analytical requirements
Conceptual thinking and metrology concepts by Uri Shafrir; Ron S. Kenett (585-590).
In introducing the term ‘concept’, the authors of the 2008 International vocabulary of metrology ‘Basic and general concepts and associated terms’ (VIM, 2008) recognize that in order to operationalize a globally accepted set of metrology terms, one requires to deal with a higher level of abstraction. Concepts are obviously not specific to metrology–handling complex tasks in any domain of knowledge that requires conceptual thinking abilities. In this short white paper, we discuss how to assess and develop conceptual thinking of professionals in service, business, and industrial environments. The approach builds on a proven methodology called MERLO that has been developed in the last 15 years by experts in psychology and education with adaptation to new interactive technologies such as clickers and internet-based formative assessments. MERLO pedagogy can be used to assess individuals’ inherent conceptual thinking abilities and train them to enhance their competence in analyzing complex conceptual situations. This is pertinent to the education of metrology, quality, and statistical thinking. We suggest that MERLO can be considered as a complementary enabler to VIM, so that this fundamental work can enhance its impact and applicability.
Keywords: Metrology; Concepts; Conceptual thinking; Concept parsing algorithms; Information quality; Post-failure reflectivity
Document control: status of calibration/test certificate by Mahesh Chander Gupta (591-593).
The ISO/IEC 17025 standard requires that all documents that form part of the management system of the organization must be controlled. However, as customary, the certificates issued from testing or calibration laboratories do no bear any unique identity mark/number similar to other documents to announce control over the document. This leaves enough room for doubt to many in treating this document at par with other management system documentation. Some auditors had raised this question during accreditation visits.
Keywords: Document control; Quality management; Accreditation; Test reports; Calibration certificates
Report on the 33rd Meeting of ISO/REMCO by Hendrik Emons; Stephen R. Davies; John P. Hammond; Stéphane Sauvage (595-597).
Congress, conferences, workshops and courses (599-600).