Quality control reference standard material

The establishment of performance criteria for a given tumor marker test is not a simple process because accuracy and precision are unique for each type of analyte and its application. Establishing methodological limits for accuracy, precision, sensitivity, and specificity often requires standard reference materials, quality control materials, comparative studies, and actual clinical specimens. Accuracy and precision must be measured over the analyte reportable range for which the device is intended to be used. Sensitivity and specificity must be considered with respect to the intended clinical use of the device. Also, the indications for use should be carefully considered in the design of the study protocol. The indications for class II should be to monitor residual tumor after surgery (or radiation), the recurrence of tumor, or response to therapy. A 510(k) must provide clear evidence that the device is accurate, safe, effective, and substantially equivalent to a device legally marketed in the United States. 

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. 

Ievin BC, Cheng H and Reeder DJ (1999) A human mitochondrial DNA standard reference material for quality control in forensic identification, medical diagnosis, and mutation detection. Genomics 55 135-146. 

These principles are supported by a related set of studies that showed reliable inter-laboratory IHC staining for Her2/neu, ER, and so on could be achieved based on optimal AR-IHC protocols and stringent quality control using standard reference materials, even though ischemia time itself was uncontrolled and unknown.38 0... 

To understand the importance of using standards, reference materials and quality control samples. 

For most of the laboratories, additional quality control (QC) samples were inserted within each batch of samples sent. These included sample site duplicates, sample splits for analytical duplicates, a suite of USGS-prepared standard reference materials (SRMs), and... 

Water samples (drinking water, rain, sea, river or waste water and others) have been characterized by ICP-MS with multi-element capability in respect to metal impurities (such as Ag, Al, As, Ba, Be, Ca, Cd, Cr, Co, Cu, Fe, Hg, K, Na, Sb, Se, Mg, Mn, Mo, Ni, Pb, Tl, Th, U, V and Zn) in many laboratories in routine mode with detection limits at the low ng I 1 range using ICP-QMS, and below by means of ICP-SFMS. Drinking water samples are controlled in respect of the European legislation (Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption). For quality control of analytical data, certified standard reference materials e.g. drinking water standard (40CFR 141.51), river water reference material SLRS-4 or CASS-2 certified reference sea-water material and others are employed. 

Interlaboratory Quality Control. In addition to the mandatory quality control practices just outlined, the laboratory is encouraged to participate in interlaboratory programs such as relevant performance evaluation (PE) studies, analysis of standard reference materials, and split sample analyses. Participation in interlaboratory analytical method validation studies is also encouraged. 

Control charts are used in many different applications besides analytical measurements. For example, in a manufacturing process, the control limits are often based on product quality. In analytical measurements, the control limits can be established based on the analyst s judgment and the experimental results. A common approach is to use the mean of select measurements as the centerline, and then a multiple of the standard deviation is used to set the control limits. Control charts often plot regularly scheduled analysis of a standard reference material or an audit sample. These are then tracked to see if there is a trend or a systematic deviation from the center-line. 

Certified reference materials are expensive to produce and correspondingly expensive to purchase. They should therefore be used sparingly and looked after carefully to avoid contamination. Many analysts prefer to produce their own standard reference materials in bulk for quality control purposes. Care is needed to make sure that such a standard material is homogenized as well as possible, which usually involves producing a material with a very fine particle size. 

Quality assurance is part of the regulations specified by the national standards organizations such as the Nuclear Regulatory Commission. Quality assurance applies to any material or component or a fabricated structure in the sense that their satisfactory performance in service conditions is assured. The quality assurance and control programs in Canada are contained in Canadian Standards Association document CAN3-Z 299.1-85 consisting of four parts. The four parts of the standard are such that Part 1 covers quality assurance, Part 2 refers to quality control, Part 3 refers to quality verification, and Part 4 deals with quality inspection. 

Of additional benefit to enantioselective POP separations is the quantification of enantiomer compositions in standardized reference materials, available from sources such as the US National Institute of Standards and Technology (NIST) and Environment Canada [105, 106]. Such materials are intended for quality assurance/quality control in sample processing and instrumental analysis of their respective matrices, and enantiomer quantification extends this use to enantioselective studies. 

The particle size distributions of 15 International Atomic Energy Agency and 16 National Institute of Standards and Technology reference materials (RMs) were measured by laser diffraction to determine their potential as reference or quality control materials in that less than 100 mg are required. Most of the materials are commercially available as environmental and biological reference materials (RMs) [137]. 

Zambia, Thailand and USA (Florida) were analyzed by using the X-ray fluorescence method for elemental composition. These rock phosphates have also been evaluated for their agronomic effectiveness by means of radioisotope techniques (Zapata and Axmann, 1991). The samples were prepared as pellets and analyzed using the emission transmission method for trace elements (Markowicz and Haselberger, 1992). All samples were excited using an Mo tube with an Mo secondary target. For quality control of concentration data analysis of standard reference material CRM 032 (phosphate rock) produced by CEC, Brussels, has been used. Satisfactory agreement between certified and measured values was obtained. 

Where available, reference materials need to be used for calibration or quality control. The National Institute of Standards and Technology (NIST) and many commercial sources supply such materials. Many high performing technology laboratories are capable of preparing their own reference materials using the same approach used by NIST in certifying their Standard Reference Materials (SRM). The calibration reference materials (RM) should be traceable to national standards, and the traceability must be preserved in the laboratory s documentation system. 

There is still a large need for the preparation of reference materials certified for arsenic compounds in various matrices, such as food, urine, and water. Currently, only standard reference materials prepared from fish are available. These materials will help to prepare quality-controlled data on arsenic compounds and, of course, establish speciation analysis in routine laboratories. 

SIMS is used for quantitative depth profile determinations of trace elements in solids. These traces can be impurities or deliberately added elements, such as dopants in semiconductors. Accurate depth prohles require uniform bombardment of the analyzed area and the sputter rate in the material must be determined. The sputter rate is usually determined by physical measurement of the crater depth for multilayered materials, each layer may have a unique sputter rate that must be determined. Depth prohle standards are required. Government standards agencies like NIST have such standard reference materials available for a limited number of applications. For example, SRM depth profile standards of phosphorus in silicon, boron in silicon, and arsenic in silicon are available from NIST for calibration of SIMS instmments. P, As, and B are common dopants in the semiconductor industry and their accurate determination is critical to semiconductor manufacture and quality control. 

Technology (NIST), formerly the National Bureau of Standards founded in 1918, is responsible for maintaining both scientific and commercial metrology in the United States. Its mission is to promote American innovation and competitiveness and supplies industry, academia and government with certified standard reference materials, including documentation for procedures, quality control, and materials for calibration. The German Institute for Standards (DIN) was founded in 1917 while in the United Kingdom the BSI was formed in 1901. 

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