Proficiency standards

Internal methods of quality assessment should always be viewed with some level of skepticism because of the potential for bias in their execution and interpretation. For this reason, external methods of quality assessment also play an important role in quality assurance programs. One external method of quality assessment is the certification of a laboratory by a sponsoring agency. Certification is based on the successful analysis of a set of proficiency standards prepared by the sponsoring agency. For example, laboratories involved in environmental analyses may be required to analyze standard samples prepared by the Environmental Protection... 

ATP, Odor Recognition Proficiency Standard for Explosive Detection Canines, 2005. 

It is essential that minimum proficiency standards for key safety-related activities are specified, achieved, and maintained. The range of activities for which an individual will be expected to maintain proficiency will depend on the duties assigned, and will be specified in the relevant post description. The Head of the Health and Safety Office will be responsible for ensuring that proficiency standards are met and maintained. 

The individual scientist is the key to the production of quality data and must have technical competence and a dedication to quality work. Passive following of good laboratory practices and good measurement practices is not enough. Involvement in their development is required if the quality assurance program is to be credible. Standard operations procedures (SOPs) do not minimize the need for technical competence. Analysts exhibit varying degrees of proficiency when... 

Many experts in Europe have tested the methods of both standards with various pesticide-matrix combinations in their own laboratories. Consequently, the responsible working groups of CEN TC 275 concluded that these are the best methods available. Nevertheless, there is no complete validation of all possible pesticide-matrix combinations. However, for most multi-residue methods within the standards all those pesticides which had been successfully tested in method validation trials and/or proficiency tests are listed. Also, matrices which had been examined in ring tests are listed. 

The magnitude of these errors can be analyzed in single laboratories (run bias and repeatability error), in inter-laboratory validation studies (laboratory bias) and in proficiency tests (method bias). Expressed in standard deviations relative to that of... 

Numerous radon and radon decay measurements in houses are now being made by a large number of private and governmental organizations. In order to assure valid and consistent measurements, it is important that proven methods be used following standardized procedures. To address this need, EPA issued "Interim Indoor Radon and Radon Decay Product Measurement Protocols" and established a Radon/Radon Progeny Measurement Proficiency program. 

Vani K, Sompuram SR, Fitzgibbons P, et al. National HER2 proficiency test results using standardized quantitative controls. Arch. Pathol. Lab. Med. 2008 132 211-216. 

There is no experimentally established optimum frequency for the distribution of samples. The minimum frequency is about four rounds per year. Tests that are less frequent than this are probably ineffective in reinforcing the need for maintaining quality standards or for following up marginally poor performance. A frequency of one round per month for any particular type of analysis is the maximum that is likely to be effective. Postal circulation of samples and results would usually impose a minimum of two weeks for a round to be completed and it is possible that over-frequent rounds have the effect of discouraging some laboratories from conducting their own routine quality control. The cost of proficiency testing schemes in terms of analysts time, cost of materials and interruptions to other work has also to be considered. 

If the analytical method used by participants in the proficiency testing round has been validated by means of a formal collaborative trial, then the repeatability and reproducibility data from the trial can be used. The repeatability standard deviation gives an estimate of the expected variation in replicate results obtained in a single laboratory over a short period of time (with each result produced by the same analyst). The reproducibility standard deviation gives an estimate of the expected variation in replicate results obtained in different laboratories (see Chapter 4, Section 4.3.3 for further explanation of these terms). 

Proficiency Testing by Interlaboratory Comparisons - Part 1 Development and Operation of Proficiency Testing Schemes , ISO/IEC Guide 43-1 1997, International Organization for Standardization (ISO)/International Electrotechnical Commission (IEC), Geneva, Switzerland, 1997. 

Chapter 7 Response 7.1 (a) The mean, standard deviation, robust average (median) and robust standard deviation (MADe) are shown in Table SAQ 7.1. Table SAQ 7.1 Data from a proficiency testing round for the determination of moisture in barley ... 

TOEFL w/2 cassettes Verbal Review for Standardized Tests Writing Proficiency Examinations You Can Pass the GED"... 

Thus, as for the European Union, the requirements are based on accreditation, proficiency testing, the use of validated methods of analysis and, in addition, the formal requirement to use internal quality control procedures which comply with the Harmonised Guidelines. Although the EU and Codex Alimentarius Commission refer to different sets of accreditation standards, the ISO/IEC Guide 25 1990 and EN 45000 series of standards are similar in intent. It is only through these measures that international trade will be facilitated and the requirements to allow mutual recognition to be fulfilled will be achieved. 

As shown above, these include a laboratory to be third-party assessed to international accreditation standards, to demonstrate that it is in statistical control by using appropriate internal quality control procedures, to participate in proficiency testing schemes which provide an objective means of assessing and documenting the reliability of the data it is producing and to use methods of analysis that are fit-for-purpose . These requirements are summarised below and then described in greater detail later in this chapter. 

Most proficiency testing schemes compare bias with a standard error. An obvious approach is to form the z-score given by ... 

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