Standard reference material quality

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. 

Wise SA (1993) Standard reference materials for the determination of trace organic constituents in environmental samples. In Barcelo D, ed. Environmental Analysis Techniques, Applications and Quality Assurance, pp 403-446. Elsevier Science Publishers, Amsterdam, The Netherlands. Wise SA, and Schantz MM (1997) Standard reference materials for the determination of trace organic contaminants in environmental samples. In Clement R and Siu M, eds. Reference Materials for Environmental Analysis Making and Using Them, pp 143-186. Lewis Publishers, Boca Raton, FL. 

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. 

In the field of RM certification, NAA represents a major analytical technique. It possesses unique quality assurance and self-verification aspects. Not surprisingly, therefore, NAA has been used to certify NIST standard reference materials [470]. By analogy, NAA has also been instrumental in analysing the EC polymer reference materials within the framework of the PERM project [1]. NAA was also used to validate a TXRF procedure for the determination of additives containing Ti, Zn, Br, Cd, Sn, Sb and Pb [56],... 

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... 

STANDARD REFERENCE MATERIAL CELL LINE DEVELOPMENT AND USE OF REFERENCE CELL LINES AS STANDARDS FOR EXTERNAL QUALITY ASSURANCE OF HER2 IHC AND ISH TESTING... 

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

Equipment Maintenance/Calibration/Monitoring Method Validation Standard/Reference Material Storage of Labile Components Laboratory SOPs Testing Quality Identity... 

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... 

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. 

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. 

Furthermore, isotope standard reference materials are required in different chemical forms for a multitude of elements in order to calibrate and evaluate isotope ratio measurements by mass spectrometry. In addition, reliable analytical data required in science and routine work will only be obtained by improving the quality assurance of the measurement procedures and also using interlaboratory comparisons of analytical results in round robin tests. 

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. 

Note PS = primary standard APS = compounds that approach primary standard quality NIST = compounds sold as primary standards by the NIST Standard Reference Materials Program, 100 Bureau Drive, Gaithersburg, MD 20899-3460 (www.nist.gov). 

The levels of accuracy and precision determine the quality of a measurement. The data are as good as random numbers if these parameters are not specified. Accuracy is determined by analyzing samples of known concentration (evaluation samples) and comparing the measured values to the known. Standard reference materials are available from regulatory agencies and commercial vendors. A standard of known concentration may also be made up in the laboratory to serve as an evaluation sample. 

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. 

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. 

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. 

It is worth mentioning that certified reference data were not available for the elements aluminum, titanium, vanadium, boron, nickel, and phosphorus at the time of analysis. This is a frequent problem in multielement analyses. It is diflBcult to obtain standard biological reference materials similar to the samples being analyzed with more than but a few certified analytical results. The lack of standard reference material limits quality assurance review of the data and diagnosis of analytical problems. The recent issue of new standards such as spinach leaves and brewers yeast will improve the material variety. Certification of more elements in the existing standards will also greatly assist the analyst. 

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