Quality assurance proficiency testing

Keywords Traceability Gas standards Calibration Quality assurance Proficiency testing International comparisons... 

An active program of surveillance of the quality of the immunostains produced must be defined. The primary elements of such a quality assurance (QA) program include procedures and policies for patient test management, quality control, proficiency testing, comparison of test results, relationship of clinical information to patient test results, personnel assessment, communications, complaint investigations, QA review with staff, and QA records. The documentation and review by the laboratory director of all QA procedures is imperative and cannot be overstressed. A brief explanation of each of the QA elements is as follows ... 

The ISO 17025 standard [3] describes monitoring the quality assurance of test and calibration results by, amongst other means, the regular use of CRMs and/or internal quality control using secondary reference materials and by participation in inter-laboratory comparisons or proficiency testing programmes. 

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). 

This chapter deals with handling the data generated by analytical methods. The first section describes the key statistical parameters used to summarize and describe data sets. These parameters are important, as they are essential for many of the quality assurance activities described in this book. It is impossible to carry out effective method validation, evaluate measurement uncertainty, construct and interpret control charts or evaluate the data from proficiency testing schemes without some knowledge of basic statistics. This chapter also describes the use of control charts in monitoring the performance of measurements over a period of time. Finally, the concept of measurement uncertainty is introduced. The importance of evaluating uncertainty is explained and a systematic approach to evaluating uncertainty is described. 

The previous chapters of this book have discussed the many activities which laboratories undertake to help ensure the quality of the analytical results that are produced. There are many aspects of quality assurance and quality control that analysts carry out on a day-to-day basis to help them produce reliable results. Control charts are used to monitor method performance and identify when problems have arisen, and Certified Reference Materials are used to evaluate any bias in the results produced. These activities are sometimes referred to as internal quality control (IQC). In addition to all of these activities, it is extremely useful for laboratories to obtain an independent check of their performance and to be able to compare their performance with that of other laboratories carrying out similar types of analyses. This is achieved by taking part in interlaboratory studies. There are two main types of interlaboratory studies, namely proficiency testing (PT) schemes and collaborative studies (also known as collaborative trials). 

Traditionally, the education that chemists and chemistry laboratory technicians receive in colleges and universities does not prepare them adequately for some important aspects of the real world of work in their chosen field. Today s industrial laboratory analyst is deeply involved with such job issues as quality control, quality assurance, ISO 9000, standard operating procedures, calibration, standard reference materials, statistical control, control charts, proficiency testing, validation, system suitability, chain of custody, good laboratory practices, protocol, and audits. Yet, most of these terms are foreign to the college graduate and the new employee. 

Analytical method validation forms the first level of QA in the laboratory. Analytical quality assurance (AQA) is the complete set of measures a laboratory must undertake to ensure that it is able to achieve high-quality data continuously. Besides the use of validation and/or standardized methods, these measures are effective IQC procedures (use of reference materials, control charts, etc.), with participation in proficiency testing schemes and accreditation to an international standard, normally ISO/IEC 17025 [4]. Method validation and the different aspects of QA form the subject of Section 8.2.3. 

Wang, W, Zheng, J, Tholen, D W, Cao, Z, and Lu, X (2005), A statistical strategy for discouraging collusion in split-level proficiency testing schemes. Accreditation and Quality Assurance, 10 (4), 140-43. 

Increasingly a price of accreditation is mandatory participation in proficiency testing schemes. If the scheme test materials really do match the routine analyses performed by the laboratory, proficiency testing gives an excellent assurance to both the laboratory and the client as to the quality of the laboratory s results. If the scheme has assigned quantity values for the test materials sent out, the cohort as a whole can be judged, and biases at the sector level discovered. 

There are proficiency testing programs that are geared toward clinical sensitivity or specificity by seeking to determine whether a disease can be detected versus other types of controls that are use to test sensitivity, selectivity, and most importantly, reproducibility and precision. With mass spectrometry, the controls are and should be no different than those used for other assays, with one interesting exception. Quality assurance materials prepared for MS/MS may not be useful in other assays that are less selective. The example is newborn screening where quality assurance/control QA/QC materials have a mixture of compounds present in the blood specimens. However, in less selective immunoassays, the mixture creates interferences. In addition, material is used to spike a blood sample is key and one should ensure there is no enzyme activity. We have encountered such a problem with a d/1 mixture of metabolites where one form was degraded in the prepared blood. 

The proficiency test provider and reference laboratory may be the same organizational entity. If not, they must closely coordinate and document their quality assurance procedures and division of responsibilities. For a test round to be successful, each laboratory under test must receive a sample which is the same as every other sample from the lot, within the limits specified for the test. This means that careful attention must be given to material packaging, stability, and handling during distribution. 

This paper has described new approaches to providing quality assurance within the operation of proficiency evaluation programs. The approaches are used in a new NIST program to monitor providers of proficiency testing in an environmental field. A part of that monitoring is conducted by means of indirect proficiency evaluation of the providers. The new program demonstrates that both direct and indirect proficiency evaluation can provide traceability links, in chemical metrology, to measurements carried out at NIST. 

Before the designation, the laboratories developed their laboratory methods for testing, constructed and made operational their laboratory quality system and obtained its accreditation, and continued the participation and successful performance in the OPCW proficiency tests (PT). Analytical methods in particular and a certain level of quality assurance systems have existed in the laboratories, involved often in research, well before their designation. Participation in the international interlaboratory... 

The Technical Services function of AOCS establishes, revises, and annually updates AOCS Methods, the Official Methods and Recommenced Practices of the American Oil Chemists Society22 for fats, oils, and soap technology Spanish AOCS Methods, a Spanish translation of the more commonly used AOCS Methods and Physical and Chemical Characteristics of Oils, Fats and Waxes. Leaders of the methods development committees coordinate closely with AOAC International (formerly the Association of Official Analytical Chemists). AOCS Methods are recognized as Official Methods in US FDA activities and when litigation becomes necessary in industry trade. Additionally, the Technical Services function operates a Laboratory Proficiency Program (formerly the Smalley Check Sample Program) and oversees distribution and statistical analysis of 30 different series of basic laboratory quality assur-ance/quality control test samples. Certification as AOCS Approved Chemists, or as AOCS... 

The term quality control (QC) is applied to procedures used to provide evidence of quality and confidence in the analytical results. It includes use of blanks, replication, analysing reference materials or other well-defined samples and participation in Proficiency Testing schemes. Several other features of analysis forming part of QC are control of reagents and instrumentation, equipment maintenance and calibration, and procedures for checking calculations and data transfer. It should be noted that what is referred to as quality assurance in the UK is known as quality control in Japan. 

A Proficiency Test (PT) is defined as the study of laboratory performance by means of ongoing interlaboratory test comparisons . It is also known as an external quality assessment scheme, external laboratory performance check or external quality assurance (EQA). There are many such schemes run by independent external bodies for different analytes in a variety of matrices. Evidence in published papers shows that the performance of analytical laboratories improves as a result of participating in Proficiency Testing schemes and the betw een-laboratory precision can improve, sometimes dramatically. This is especially true in the early years of participation. 

Nowadays it is generally accepted that laboratory proficiency testing schemes are an important quality assurance tool in environmental monitoring programmes. Apart from using validated analytical methods and internal laboratory quality control procedures, the regular participation of laboratories in interlaboratory comparisons is required to ensure the accuracy and comparability of data. 

Quality measurements have several elements. Quality assurance plans and quality control procedures are an essential beginning. In addition, it is necessary to have qualified scientists whose training needs to be documented and updated on a continuous basis. Quality measurements also require proper use of reference materials where available, and laboratories must repeatedly test their ability to perform through taking part in proficiency testing schemes. The provision of another essential element in quality measurements, namely validated methods, is the primary contribution from the work of AOAC. 

---