Development Of Reference Methods Research Articles

The evolution of selective analyses of HDL and LDL cholesterol in clinical and point of care testing

Cardiovascular disease is a leading cause of death worldwide and is caused by the build up of atherosclerotic plaques in the vasculature. It is now well established that the formation of these plaques is closely related to levels of both high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol. Thus, the importance of the effective measurement of these is critical for the improved diagnosis and management of atherosclerosis. This review discusses the emergence of methodologies for the selective determination of both LDL and HDL cholesterol. It begins with an explanation of the first methodologies based on ultracentrifugation and precipitation techniques, the development of reference methods, through to the emergence of methodologies suitable for routine laboratory use, followed by the development of professional use, point of care technologies. Finally, the current status of selective tests for cholesterol based on biosensor methodologies is reviewed and the potential for application in consumer diagnostics is discussed.

Reference Methods and Materials for Vitamin D Metabolites: Importance for International Data Comparability

Vitamin D has been the subject of intense interest in recent years, not only because of its role in bone health, but also because of the potential link between vitamin D status and the risk of cancer, diabetes, and other diseases. Considerable effort has been devoted to examining the vitamin D exposure of various populations and determining the levels of circulating vitamin D metabolites that are associated with optimal health. Accurate assessment of vitamin D status is also important for identifying individuals with vitamin D deficiencies and for effective treatment. However, the value of vitamin D testing in these applications has been limited by poor comparability between different methods for 25-hydroxyvitamin D [25(OH)D], the major circulating metabolite of vitamin D. In addition, until recently, there was no mechanism to assess the accuracy of any of the methods being used. The Analytical Chemistry Division at the National Institute of Standards and Technology (NIST) is helping to ensure the accuracy and comparability of 25(OH)D measurements through the development of reference methods and Standard Reference Materials (SRMs) for vitamin D metabolites. SRM 972 Vitamin D in Human Serum, and the subsequent SRM 972a Vitamin D Metabolites in Human Serum, represent the first steps toward establishing an accuracy base for measurement of 25(OH)D in individuals and across populations. Value assignment of these reference materials has been performed using multiple higher-order methods. NIST has also initiated a measurement quality assurance program for vitamin D metabolites to assist laboratories in improving accuracy and comparability. Acknowledgements: Partial funding for this work was provided by the National Institutes of Health (NIH), Office of Dietary Supplements (ODS) through an interagency agreement

Indicators and methods for folate, vitamin B-12, and vitamin B-6 status assessment in humans

Nutritional status assessment is a critical tool for the identification of nutrient deficiencies or excesses in individual healthcare and epidemiologic screening. Because low but 'normal' status of folate, vitamin B-12, and vitamin B-6 have been associated with an increased risk of chronic diseases, research has focused on defining sensitive indicators of B-vitamin status and on the development and validation of analytical methods for their quantification. With the increasing availability and more user-friendly configuration of liquid chromatograph-tandem mass spectrometers (LC-MS/MS), numerous analytical methods for determination of B-vitamin indicators by LC-MS/MS have been developed over the last years. These methods include folate assays for simultaneous determination of numerous folate forms at their specific reduction level. The functional indicators for vitamin B-12 status are plasma methylmalonic acid and total homocysteine and can be measured, either individually or in combination, by high-throughput analysis using LC-MS/MS. Methods for vitamin B-6 status assessment are multianalyte platforms that determine vitamin B-6 forms and functional indicators by the same assay. The high sensitivity, selectivity, and specificity of isotope-dilution LC-MS/MS [and gas chromatography-mass spectrometry (GC-MS)] techniques have allowed the development of reference methods and the creation of multianalyte platforms. The additional convenience of automated sample preparation enables high sample throughput and makes those sensitive methods prospective analytical candidates for larger settings including clinical laboratories.

Nucleic acid reference materials (NARMs): definitions and issues

Molecular diagnostics is one of the most rapidly growing areas of laboratory medicine. This rapid growth of clinical molecular tests has outpaced the availability and development of reference methods and reference materials. Such methods and materials are important for the development, validation, and interpretation of diagnostic methods and tests. Yet, there is a lack of harmonization between the numerous international organizations currently either certifying or defining reference materials. The objective of this position paper is to review and clarify the definition, attributes and applications for the use of reference materials in the context of molecular diagnostics.

The Development of Reference Methods in Clinical Chemistry. The contribution of the Community Bureau of Reference of the Commission of the European Communities

The use of reference method procedures in clinical chemical analysis is advocated by many experts as the most reliable approach to obtaining accurate results. The performance of such procedures must, however, be rigorous. This contribution will emphasize the importance of interlaboratory studies for this purpose. Examples will be presented, taken from the work done under the BCR programme of the Commission of the European Communities. The determination of steroid hormones in serum by isotope dilution mass spectrometry and the measurement of enzyme catalytic activities, according to IFCC recommended methods, will be discussed.

Development, Testing and Intercalibration of Reference Methods for Pollution Studies in Coastal and Estuarine Waters

Following the 1972 United Nations Conference on the Human Environment, the United Nations Environment Programme (UNEP) initiated a Regional Seas Programme in 1974. At present the Programme involves ten regions and has over 120 coastal states participating. It is conceived as an action-orientated programme having concern not only for the consequences but also for the causes of environmental degradation and encompassing a comprehensive approach to combating environmental problems through the management of marine and coastal areas. Each regional action plan is formulated according to the needs of the region as perceived by the governments concerned. The overall strategy of the programmes was defined by UNEP's Governing Council as:Promotion of international and regional conventions, guidelines and actions for the control of marine pollution and for the protection of management of aquatic resources.Assessment of the state of marine pollution, of the sources and trends of this pollution, and of impact of the pollution on human health, marine ecosystems, and amenities.Co-ordination of the efforts with regard to the environmental aspects of the protection, development and management of marine and coastal resources.Support for education and training efforts to make possible the full participation of developing countries in the protection, development and management of marine and coastal resources. One of the basic components of the regional action plans is the assessment of the state of marine pollution. For this purpose a set of Reference Methods for marine pollution studies is being developed. The paper describes the development of Reference Methods for use by participants in Regional Seas Programmes, where they are intended to ensure that the data can be compared on the world-wide basis and thus contribute to the Global Environment Monitoring System (GEMS) of UNEP. Also, the basis for the Reference Methods as a basis by which countries can adopt comparable methods of assessing the extent of marine pollution in the event of inter-governmental disputes is explained. The Reference Methods being developed cover a wide range of pollutants, e.g. trace metals, chlorinated hydrocarbons, petroleum hydrocarbons, tar, bacteria, etc., as well as providing guidelines for sampling strategies, preparation of samples, toxicity tests, data handling and evaluation. In addition, they include information on how basic oceanographic parameters are to be assessed and used to supplement the data on marine pollution. The paper draws on particular aspects of the development and testing of some individual Reference Methods to illustrate the problems and philosophy adopted for a project which represents a world-wide attempt to promote the detection, understanding and control of coastal and estuarine pollution. The scientific criteria for method selection and application emphasize the pragmatic approaches which are being adopted to fulfil this ambitious project.

Isotope dilution — high-performance liquid chromatography as a new technique for the development of reference methods

Isotope dilution — high-performance liquid chromatography as a new technique for the development of reference methods