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Calibration and Traceability
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
As discussed above, a primary standard generally represents the highest level of measurement quality in a measurement chain and is generally held by a national metrology institute. Because of the amount of resources necessary to prepare such a standard, they are generally not directly distributed to users. Moreover, it is common practice for most national metrology institutes to transfer a primary standard to another instrument that is less resource-intensive and that preferably enables the measurement of multiple sources at a time. One such instrument is a re-entrant ionization chamber, commercial versions of which are known as ‘activity meters’, ‘activity calibrators’, or ‘dose calibrators’.
Reference Dose Determination under Reference Conditions
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
At the outset, it can be useful to explain what is meant by the concept of a primary standard. According to McEwen (2009), this is:“A Standard that is designated or widely acknowledged as having the highest metrological qualities and whose value is accepted without reference to other standards of the same quantity.”
Calorimetry
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Larry A. DeWerd, Blake R. Smith
Calorimetry is used to realize the primary standard for absorbed dose to water. A primary standard is a device that measures a physical quantity directly from the fundamental quantities of substance quantity (mol), length (meter), mass (kilogram), time (second), charge or current (Coulomb or Ampere), temperature (Kelvin), and light intensity (candela). The basis of calorimetry is simple, but its practice is complicated. A good summary is given in Chapter 15 of the AAPM 2009 summer school [1]. Historically, in 1904, Curie and Dewar developed the first cryogenic calorimeter and the history continues to the present day at various temperatures. Calorimetry is the determination of energy absorbed, generally expressed in a temperature rise. For water, the increase in temperature is approximately 2.4 × 10−4 K/Gy or about 0.24 mK/Gy. There are complicating factors involved in water calorimetry that will be addressed later. The quantity of absorbed dose, Dm, for a material, m, is determined from a change in energy, , that is measured from the material's temperature change
Pharmacopeial Standards for the Quality Control of Botanical Dietary Supplements in the United States
Published in Journal of Dietary Supplements, 2023
Nandakumara Sarma, Roy Upton, Ulrich Rose, De-an Guo, Robin Marles, Ikhlas Khan, Gabriel Giancaspro
Pharmacopeial public standards ensure a nomenclature for products and help ensure the quality and consistency of these products. Without public standards, only private specifications exist. For dietary supplements, this means that the analytical tests establishing identity, strength, and purity are generally kept confidential and are not available for public review; in addition, the specifications set by each manufacturer may not be uniform across the industry. Two manufacturers may each make Echinacea products, for example, but under the current law and regulation, the consumer will not know the standards to which each product is held and will be unable to determine whether the two products are similar or how they differ. When different manufacturers of a product utilize the same standards, they meet certain specifications according to analytical tests that ensure a product’s identity, strength, and purity. Further, pharmacopeial reference standards allow the regulators to analyze materials without having to establish the suitability of the secondary material and its traceability to the primary standard.
Inter-assay variability in automated serum free light chain assays and their use in the clinical laboratory
Published in Critical Reviews in Clinical Laboratory Sciences, 2020
Laura Caponi, Nadia Romiti, Elona Koni, Annarita Di Fiore, Aldo Paolicchi, Maria Franzini
The Freelite® assay (The Binding Site Group Ltd, Birmingham, UK) was commercialized in 2001 for the immunochemical quantification of serum FLC on automated platforms [61]. Polystyrene latex particles were coated with sheep polyclonal anti-κ and anti-λ FLC antibodies. The antibodies were obtained from tolerized sheep immunized with a polyclonal preparation of human FLC purified from urine samples; the resultant antisera were then absorbed with intact immunoglobulins and affinity-purified against mixtures of the respective FLC [61]. The reaction is enhanced by the addition of polyethylene glycol. The primary standard consists of polyclonal κ and λ FLC obtained by the reduction and acetylation of polyclonal IgG purified from a serum pool from 200 apparently healthy subjects. Calibration materials provided in the Freelite kits consist of human serum containing FLC that are referenced to the primary standard. The Freelite reagents have been adapted to several nephelometric and turbidimetric platforms.
Maintaining consistent quality and clinical performance of biopharmaceuticals
Published in Expert Opinion on Biological Therapy, 2018
William C. Lamanna, Johann Holzmann, Hillel P. Cohen, Xinghua Guo, Monika Schweigler, Thomas Stangler, Andreas Seidl, Martin Schiestl
Product consistency is therefore maintained by the combination of many tools at different layers throughout the product life cycle. In addition, detailed improvements are encouraged to further reduce the risk of inconsistency. For example, to verify that analytical test results are consistent over time, a two-tiered reference standard strategy has been proposed by regulators and has been quickly adopted by industry [74]. As shown in Figure 3, this two-tiered approach dictates that any official or ‘in house’ reference standard for routine testing must be qualified or calibrated against a single primary reference standard, and subsequently tested at regular intervals against the primary standard to detect any drift of the reference standards. This strategy is another feature to maintain consistent analytical test results and preserve a reliable link between analytical data and clinical studies throughout the product life cycle.