Proficiency tests

Analytical Methods Committee, Handling false negatives, false positives and reporting limits in analytical proficiency tests. Analyst, 122, 495, 1997. 

General Lab. and Pharma. Lab. participate In proficiency-testing studies and market surveillance studies organised by European Department for Quality of... 

Peer review This involves setting up mechanisms for mutual review of dmg regulation systems. It serves as a means of external auditing, whereby the performance of one agency can be compared with that of others. Systems for international peer comparison of QC laboratories are one example. Proficiency tests are performed by the participating laboratories in such a way that each laboratory learns how well it is performing in comparison with the others. 

It must be remarked that terminology is not consistent and there are many widely used synon)ms. Quality control in this Chapter refers to practices best described as internal quality control. Quahty assessment is often referred to as external quality control, proficiency testing, interlaboratory comparisons, round robins or other terms. Internal Quality Control and External Quality Assessment are preferred because they best describe the objectives for which the RMs are being used, i.e. the immediate and active control of the results being reported from an analytical run or event, and an objective, retrospective assessment of the quality of those results. 

Thompson M, Wood R (1993) International harmonized protocol for proficiency testing of (chemical) analytical laboratories. J of AOAC Intern 76 926-937. 

Assuming an analytical error of 2 % which is based on the analysis of the results of a number of proficiency tests and collaborative trials (Daas and Miller 1998), a maximum uncertainty of 0.24% would imply a 0.1% probability of rejecting a good result. Given that the uncertainty of a content to be assigned is below a predetermined value, the results of the collaborative trial are acceptable otherwise it is recommended to repeat the trial in whole or in part. 

The direct and immediate use of laboratory data in medical diagnostic decision making is unique, so the proper use of reference materials in conjunction proficiency testing clinical chemistry is vital if false and mis diagnosis is to be avoided. 

A number of international organizations are active in the field of clinical chemistry reference materials and proficiency testing, these include ... 

BRM-2 highlighted the distinction between primary (certified) and secondary (e.g. check samples for proficiency testing) RMs. 

As the use of RMs increases and international trade in these materials becomes established, it has become clear that they can be subject to high levels of import duty and delay when clearing customs. In 1998 ISO/REMCO established Task Group 6 to investigate the problems involved in shipping reference materials (and materials that are in the process of being made into reference materials, such as proficiency testing materials) across national boimdaries. 

Millar RC, Armishaw P, Wilson MC, Majewski l.M (1995), Recent developments in Australia-reference materials and proficiency testing. Fresenius J Anal Chem 352 28-32. 

Over the past decade, a major trend has been the development of the use of proficiency testing (PT) or evaluation materials (Fox 2000). PT materials are a type of reference material, which aid in assessment of analytical laboratory measurement quality. There will be an increased use of such materials as part of laboratory accreditation programs and other new quality assurance efforts, including internal audits. At the same time, a number of providers have used PT schemes to produce a form of RM intended to meet the ever-growing need for RMs required for routine QC use (Jenks 1995,1997). 

A similar effort by Australia to activate AQC efforts and promote proficiency testing in South East Asian and Pacific Rim Regions providing RMs for organo-chlorines and phosphates in animal fat (Millar et al. 1995),... 

Fox A (2000) AOAC International Offers Leadership in Proficiency Testing. Food Testing and Analysis, 5(6) 7-g. 

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. 

Magnitude of the response caused by a certain amount of analyte Alternatively, certified reference materials, samples analyzed with reference methods or proficiency test materials may be apphed... 

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... 

Table 14 can be regarded as providing a reasonable overall picture, even if the results cannot applied to any particular case. However, if the underlying principle is accepted, it becomes clear that improvements in a single stage, for example the reduction of instrument variation, has a negligible beneficial effect (if this variation was not outside the normal range ). Even if the contribution of repeatability is re-duced to zero, the cumulative uncertainty is reduced by 10% only, i.e. from 2.2 to y(0.0)2 (0.8)2 (1.0)2 + (1.5)2 = 2.0. This statistical view of errors should help to avoid some unnecessary efforts to improve, e.g., calibration. Additionally, this broad view on all sources of error may help to detect the most important ones. Consequently, without participation in proficiency tests, any method validation will remain incomplete. 

False-positive results with bDNA have been observed with proficiency testing specimens for HTV-1 in the College of American Pathologists HIV-1 viral load survey and HCV in the viral quality control program administered by the Netherlands Red Cross. The reason for the false-positive results with these proficiency testing specimens is not known but may be sample matrix effects. The extent to which this problem occurs with clinical samples has not been determined. However, both the HIV-1 and HCV bDNA assays were designed to have a false-positive rate of 5%. 

Proficiency testing is a special type of laboratory performance studies defined as study of laboratory performance by means of ongoing interlaboratory test comparisons (ISO Guide 33 [1989] ISO/REMCO N 280 [1993] IUPAC [1993] Prichard et al. [2001]). Proficiency testing is an essential part of external quality assessment schemes and performance checks. 

The principle of proficiency testing schemes consists in analyzing one or more samples sent to the laboratories by an external body. The analytical results returned to the organizer are evaluated in comparison to the assigned value(s) of the sample(s). 

Proficiency testing can be assessed in different ways. One of the most used evaluation system is that of so-called z-scores which are defined as follows (Lawn et al. [1993] Thompson and Wood [1993]) ... 

ISO/REMCO N 280 (1993) Proficiency testing of chemical analytical laboratories. Geneva... 

IUPAC (1993) Analytical Chemistry Division, Commission on General Aspects of Analytical Chemistry The International Harmonized Protocol for the Proficience Testing of (Chemical) Analytical Laboratories. Pure Appl Chem 65 2123... 

Lawn RE, Thompson M, Walker RF (1993) Proficiency testing in analytical chemistry. Royal Society of Chemistry, London... 

Kahlert, B. (2005a). ISTA proficiency test on GMO testing a brief overview , Seed Testing International, 129, 17-18. www.seedtest.org/upload/cms/user/STI1291.pdf. Accessed July 18, 2005. 

Organizations whose measurement results are with 25% of the known exposure level will be considered to have met the proficiency test requirements. 

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. 

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