External quality assurance systems

The importance of a careful evaluation of the performance characteristics of analytical procedures and adequate quality control against a laboratory s own requirements have been emphasized. However, it is extremely important to establish comparability between laboratories, i.e., the analytical result should be independent of the laboratory performing the analysis. An ongoing monitoring of the analytical performance against the norm of other laboratories is provided by external quality assurance systems. This external evaluation supplied by comparisons between analytical results of different laboratories estimates the between-laboratory differences. The main value of the external quality assurance systems is not only to highlight repeatability and reproducibility performance between laboratories but also to assess systematic errors. 

External quality assurance systems (EQAS) refer to systems for objectively assessing and demonstrating the reliability of laboratory results by means of interlaboratoiy comparison. Interlaboratory comparison can be performed as collaborative, prcficiency, or certification studies [7]. The ISO 5725 series of documents provide practical descriptions of methods for estimating precision and trueness by means of collaborative interlaboratory experiments [5]. 

Often the purpose of collaborative trials is to evaluate a new analytical method operated in several laboratories. According to lUPAC a collaborative study is an interlaboratory study in which each laboratory uses the defined method of analysis to analyze identical portions of homogeneous materials to assess the performance characteristics obtained for that method of analysis, e.g., specificity, selectivity, sensitivity, range, limit of quantification, limit of detection, linearity, accuracy, and precision. Only methods giving small interlaboratory variations will be adopted for use as a standard method. Attention has to be paid to the design of collaborative studies for 

Various terms may be used to describe schemes for external quality assessment, e.g., performance schemes, proficiency testing, etc. Although there are several types of schemes, they all share the common feature of comparison of a laboratory s results with those of other laboratories for establishment of trueness. 

The aims of a particular scheme should be described by the coordinator of the EQAS. In principle, the coordinator of a scheme on a regular basis distributes sample(s) to the participants. The laboratory measures the sample(s) and within a given time reports the resultfs) to the organizing laboratory or coordinator, which carries out the statistical analysis of the results. Afterward, the participating laboratories receive an evaluation report of their analytical performance in comparison with the other participants. The typical structure of the scheme is as follows (1) preparation of samples (2) distribution of samples (3) analysis of samples and submission of results and (4) statistical analysis of results and performance characteristics assessed. 

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Method Evaluation, Quality Control, and External Quality Assurance Systems of Analytical Procedures... 

Statistical Analysis of Results and Performance Characteristics. A common problem with most external quality assurance systems has been the determination of the true value for a control sample. Because the true value is an ideal concept, the data are evaluated against the estimated true value, which may be established from (1) the amount of analyte spiked to the test samples (2) a group of reference laboratories using definitive or reference methods (3) the consensus mean, which is the mean of the results obtained by the participants after exclusion of outlier. It is the responsibility of the coordinators to ensure and demonstrate that the reference values are reliable [6]. 

For external quality control currently (inter)national intercomparison programs are running frequently, e.g., the British external quality assurance system (EQAS) for Cd-B. 

Sampling is just the beginning of the analytical process. On the way from sampling to the test report a lot of different requirements for high quality measurements have to be considered. There are external quality assurance requirements on the quality management system (e.g. accreditation, certification, GLP), internal quality assurance tools (e.g. method validation, the use of certified reference material, control charts) and external quality assurance measures (e.g. interlaboratoiy tests). 

In order to implement the quality policy in the daily work, quality management systems are installed, covering quality planning, quality control, quality assurance and quality improvement. To ensure that the quality assurance system is in place and effective, external standards are used, for example the DIN EN ISO 9000 ff. standard system, commonly shortened to ISO 9000 (DIN is an acronym for Deutsches InstitutfiXr Normung, meaning German Industry Standard ). 

Preparation of the patient, sampling of specimens Pre-analytical handling of specimens Accurate and precise analytical performance Selection of appropriate, sensitive and specific methods Calibration of analytical systems Internal and external quality assurance Post-analytical handling of test results Clinical interpretation of test results Reporting process... 

Potential partnerships The National Cytology Institute can assist in establishing external quality assurance scheme and accreditation system for participating clinics. 

The reliability of the monitoring for the assessment of external and internal doses depends on many factors, including functional testing periodic maintenance and performance testing of the instruments used for these measurements the calibration methods and the quahfication of the staff involved. Likewise, the traceability of these measurements and the retrievability of dose assessments should be given appropriate consideration. An adequate quality assurance system should be implemented so as to confirm the vahdity of the results of the assessment. 

In the Intoduction to ISO 9001 it states that the quality assurance models represent three distinct forms of quality system suitable for the purpose of a supplier demonstrating its capability and for the assessment of such capability by external parties. In other words, the standard is suitable for contractual as well as for assessment purposes, but it does not actually require demonstration of capability to the assessor or purchaser unless required by the contract. 

There are two uses of chemical standards in chemical analysis. In the first place, they may be used to verify that an instrument works correctly on a day-to-day basis - this is sometimes called System Suitability checking. This type of test does not usually relate to specific samples and is therefore strictly quality assurance rather than quality control. Secondly, the chemical standards are used to calibrate the response of an instrument. The standard may be measured separately from the samples (external standardization) or as part of the samples (internal standardization). This was dealt with in Section 5.3.2. 

The management system for process definition documentation should ensure that the contents of the process documentation package are accurate and complete. A suitable review and quality assurance program should be implemented for the process documentation. This may involve a hierarchical review process, and/or using external experts in a review capacity. 

Developer May be internal or external to pharmaceutical or healthcare company s organization. He or she is responsible for the technical development, implementation, and handover of the system. This includes the quality assurance attributes of the work. 

Key players that can be identified in this process are as follows all levels of management, the persons responsible for the processes and activities to be performed under GxP, suppliers (external suppliers as well as internal system developers), IT/system managers (including service providers, if applicable), system users and Quality Assurance (QA). It is highly recommended to also involve the Purchasing and/or Legal departments in the process if new modules, updates or extensions are required. Table 13.3 indicates the basic roles, responsibilities and tasks for the key players in order to validate systems and to keep them validated. Most of the responsibilities and tasks are equally relevant for the period prior to initial validation and for keeping the systems validated. 

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