Performance of Individual Laboratories

Measurements of individual laboratory performance provides for comparisons between laboratories. It then follows to ask why some laboratories report data that are more accurate and precise than do their peers, and a well designed external quality assessment scheme allows investigation of some of the important factors (see below). A comparison of performance between individual laboratories also helps to stimulate those who are not so successful to improve (or abandon the assay) and those who do well to continue with their expertise. Finally, changes of performance may be monitored as a consequence of some new factor, e.g. purchase of a new piece of equipment, work carried out by a different analyst, change to the methodology etc. 

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To provide a measure of the quality of performance of individual laboratories. By regular testing, changes in performance can be studied. 

All proficiency testing schemes should have a statistical protocol which states clearly how the data will be processed and how laboratory performance will be evaluated. This protocol should also describe how the assigned value for any parameter in a test sample is estimated. This is an important consideration, as the performance of individual laboratories is gauged by comparison with the assigned value. 

Verification is confirmation by examination and provision of objective evidence that specified requirements have been fulfilled. ISO 9000 2005 Proficiency testing is a periodic assessment of the performance of individual laboratories and groups of laboratories that is achieved by the distribution by an independent testing body of typical materials for unsupervised analysis by the participants. [lUPAC Orange Book]... 

This review will be more concerned with the determination and maintenance of standards of precision, particularly of reproducibility, than with the assessment of accuracy and specificity of methods in clinical chemistry. This is because accuracy and specificity can be determined in a laboratory in advance of introducing a method, and the limitations of each method in these respects defined and allowed for, whereas the precision obtained for the same method may differ markedly from time to time in one laboratory and from one laboratory to another. The trials of interlaboratory accuracy (Section 1.2) have not so far been able to distinguish fully between inaccuracy and imprecision in the performance of individual laboratories for the chemical determinations under evaluation. Imprecision, however, has probably been the main factor underlying the disturbing findings revealed by these trials, and the emphasis placed in this review upon the search for improved precision and its subsequent maintenance is justified by the fact that most of the work in clinical... 

A report is distributed to the participating laboratories and may be made pubHc as part of a process of deciding if a method is to be adopted as a standard, or if the study is a Key Comparison. Usually, the performance of individual laboratories is not disclosed by the use of codes to anonymously label the participants. 

To measure the performance of individual laboratories for comparison with other participants, or for changes with time (to which licensing and/or accreditation could be added). 

Prior to drawing any conclusions on the performance of individual laboratories participating in the proficiency test, the Secretariat shall make ... 

A wide range of high quality, non-certified carotenoid and chlorophyll chemical standards are commercially available (e.g., Sigma-Aldrich, DHI, and Roth). The availability of a mixed pigment reference standard and biological matrix reference materials would improve analytical performance in individual laboratories, facilitate method and laboratory in-... 

Participance in Proficiency Testing Schemes Proficiency testing (PT) is the periodic assessment of the competency or the analytical performance of individual participating laboratories [23]. An independent coordinator distributes individual test portions of a typical uniform test material. The participating laboratories analyze the materials by their method of choice and return the results to the coordinator. Test results obtained by different laboratories are subsequently compared with each other and the performance of each participant evaluated based on a single competency score [64,107]. International harmonized protocols exist for the organization of PT schemes [59,60,64,69,79]. 

In order to know the performances of individual electrodes working in the conditions of actual cells, it is necessary to add a reference electrode. Laboratory cells have been designed for that... 

The Reflotron system produced by Boehringer Mannheim (Fig. 31) has been specially designed for the small laboratory in medical practice. An essential demand when developing this system was easy performance of individual analyses or small test series of whole blood by personnel untrained in analytical work. Furthermore, results of an individual analysis should be available in just about 2-3 minutes. More than 50000 instruments of this series have been installed world-wide in laboratories and medical practice. 

Whitehead (W6) described an IBM-870 system for the recording of laboratory data on punch cards based on an earlier description by Peacock et al. (PI). The primary purpose of this system was to improve the presentation of individual laboratory reports, but the cards were subsequently sorted and the data on them subjected to statistical analysis, some of which revealed hitherto unsuspected sources of error as a result of variation in the technical performance of individual members of staff. Whitehead was among the first to apply cusum techniques to clinical chemistry laboratory data for control purposes, but his off-line system was not able to provide quality control information of immediate value to the laboratory. 

In order to assess the overall performance of toxicological laboratories in the European Community (EC) and the applicability of analytical methods a long-term interlaboratory survey of the quality of (total) urinary arsenic and thallium was performed with twelve laboratories representing ten member countries (de Zeeuw et al., 1987). The results of the individual laboratories as well as the interlaboratory data showed in general an acceptable performance for bias and precision. 

QCPs are the means by which a quality assurance program (QAP) is implemented. A QAP is usually divided into two classifications, namely the intralaboratory (in-house) and interlaboratory (between laboratory) quality control programs. The former program is a continuing and systematic regime carried out by each individual laboratory. Unless several appropriate standard reference materials are available for the specific parameter, substrate, sample matrix, and concentration levels imder study, an in-house QAP can only reflect the performance of each laboratory in isolation. In order to assess and/or ensure the reliability and compatibility of sets of data generated by different laboratories, an interlaboratory QAP is necessary in addition to the intralaboratory QAP. 

Proficiency testing schemes are designed to test the competence of individual laboratories to perform specific analyses or a range of determinations of analytes in various matrixes and possibly using alternative techniques. 

In defining the criticality of an identified failure mode there was a debate as to whether this should be determined by considerations of patient management or more narrowly in terms of the performance of the laboratory. As the laboratory cannot always judge the importance to the doctor of an individual test result, it was decided to draw the boundary of the safety analysis around the department itself. This meant that the FMECA focused on safe handling of samples and data (both physical and electronic) within the laboratory system. 

Agency. A second example of an external method of quality assessment is the voluntary participation of the laboratory in a collaborative test (Chapter 14) sponsored by a professional organization such as the Association of Official Analytical Chemists. Finally, individuals contracting with a laboratory can perform their own external quality assessment by submitting blind duplicate samples and blind standard samples to the laboratory for analysis. If the results for the quality assessment samples are unacceptable, then there is good reason to consider the results suspect for other samples provided by the laboratory. 

It is important to make a list of every task that will be performed in the laboratory, down to the smallest detail. Operations such as pH measurements, transfer of flammables from safety storage to shelf bottles, or recording observations must not be overlooked. Even in a small laboratory, the number of individual tasks will be quite substantial. 

A very versatile piece of equipment that is affordable for individual laboratories is the microplate reader. This allows multiple samples to be analyzed at once, commonly in a 96-well format, although 384- and 1536-well formats are available. Typical measurements that can be performed include UV-Vis absorbance, fluorescence, or luminescence, allowing a range of assays to be performed, such as cell growth, enzyme kinetics, enzyme stability, or enzyme-linked immunosorbent assay [60-62]. Functionality can be increased by the use of liquid dispensing systems or automatic plate handling. 

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