Proficiency-testing test suitability

We also can take suitable data from a proficiency test (PT). In this case the laboratory must have participated in the PT successfully. We also have to consider, if the PT covered all relevant uncertainty components and steps of analysis. This includes e.g. if the matrix of the PT sample was similar to routine samples. If this is the case, we again calculate U from 2 Sr. 

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. 

Define validation, system suitability, proficiency testing. 

Residue-testing laboratories might also need to review their sample preparation processes and consider modifying or eliminating tissue homogenization prior to residue extraction. Suppliers of proficiency-testing services should also question whether certain drugs are appropriate to include in such studies. For example, liver spiked with sulfaquinoxaline, sulfadiazine, or sulfamerazine is not suitable for preparation of spiked interlaboratory check samples or reference materials. 

The ISO/IEC GUIDE 25 [1] stresses, in paragraphs 5.6 and 9.3, the importance of participation in proficiency testing programs or other interlaboratory comparisons, as appropriate and when suitable programs are available. This would imply that such activities are an important part of a laboratory s quality control procedures. 

A laboratory that has achieved accreditation is required by ISO/IEC Guide 25 to take part in proficiency testing activities, provided that a suitable program is available. ISO/IEC GUIDE 43-1 (5.5.3) states The test items or materials to be distributed should generally be similar in nature to those routinely tested by participating laboratories . 

There will often be a problem with the similarity/suitability of a proficiency test program in relation to the level at which work is usually carried out in a laboratory. If the difference is too great, traceability can no longer be claimed. It may either be the matrix that is not quite agreeable or the concentration of the analyte is at the wrong level. 

Immunoturbidimetry and immunonephelometry are widely used to measure apo A-I and apo B-lOO, which are present at relatively high concentrations. According to the College of American Pathologists Proficiency Testing Survey, all clinical laboratories in the United States that are involved in the measurement of apo A-I and apo B-lOO use one of these two approaches. Alternatively, more sensitive techniques, such as ELISA and RIA, are perhaps more suitable for those apolipoproteins present at much lower concentrations, such as apo C-I and apo C-IL Additional information about the various analytical techniques used in the determination of apolipoprotein concentrations is provided later. 

Method accuracy should be demonstrated through regular participation in suitable proficiency testing programs (when available) and use of certified reference materials in calibration (when available). 

It is a requirement of accreditation to ISQ/IEC 17025 2005 that the laboratory participates in a proficiency testing scheme, if a suitable scheme exists. The analysis of an external quality check sample as part of a laboratory s routine procedures provides objective standards for individual laboratories to perform against and permits them to compare their analytical results with those from other laboratories. 

Laboratories that are accredited to ISO 17025, rather than the well-established ISO 9000 series, are using RMs and CRMs more often and are signing up for proficiency testing (PT). ISO 17025 is the standard that provides the international aspect to any laboratory measurement process and provides the control framework to assist the production of comparable measurements. ILAC (International Laboratory Accreditation Co-operation) harmonises laboratory accreditation procedures. ISO 17025 plays an important role in international traceability and in the requirements for an internationally agreed suitable CRM. 

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