Primary Reference Materials Research Articles

MON-130 Improving the Accuracy and Reliability of Free Thyroxine (FT4) Measurements Through the CDC Clinical Standardization Programs (CSP)

Reliable free thyroxine (FT4) measurements are essential for assessing thyroid function and for correctly diagnosing and treating thyroid disorders. Thyroid hormones play an important role in normal brain development of the fetus, and abnormal FT4 during pregnancy is associated with adverse pregnancy outcomes. Standardization of FT4 measurements, is critical to improving the accuracy and reliability of current methods and thus to improve diagnosis, treatment and prevention of thyroidal illnesses. Currently, there are no serum-based reference materials available for FT4 to assess the accuracy and reliability of FT4 assays. CDC CSP is collaborating with the International Federation of Clinical Chemistry and Laboratory Medicine, and the Partnership for the Accurate Testing for Hormones to address these issues through development of an accurate and sensitive higher-order Reference Measurement Procedure (RMP) for FT4 that will be used to assign target value to serum-based materials. The CDC CSP FT4 reference method is using equilibrium dialysis in combination with liquid chromatography tandem mass spectrometry (LC-MS/MS). FT4 in serum is isolated from the binding proteins in 1 mL equilibrium dialysis cells for 4 hours at 37oC. FT4 is further isolated by extractions prior to LC-MS/MS analysis. To determine the concentration of FT4 in serum, certified primary reference materials are used to prepare calibration materials. Chromatographic separation is achieved using a C18 reverse phase column with a gradient of methanol and water with 0.1% formic acid. Quantification by selective reaction monitoring is performed in the positive mode using electrospray ionization. Two transitions are monitored for each analyte and internal standard, and triplicate injections are used to minimize instrument instability. The within- and between-day imprecision for the CDC RMP are 2.2–3.9% and 1.8–2.6%, respectively. By comparisons with the RMPs at Ghent University in Belgium, Radboud University Medical Center in the Netherlands, and the Reference Material Institute for Clinical Chemistry Standards in Japan, the CDC RMP reported a bias within +2.5% of the mean for all labs. Factors affecting measurement accuracy were investigated, to maximize recovery for optimum performance of the method. FT4 was detectable in all samples, and thus, suitable for analysis of hypo-, eu-, and hyperthyroid patients. A comparison among hypo-, eu-, and hyperthyroid patients of a commercially available immunoassay and the CDC RMP indicated a mean bias of -37.7%. The CDC CSP has also evaluated the RMP for accurate measurement of FT4 in pregnant individuals. This candidate reference method for FT4 in serum demonstrates good accuracy and precision, and can be used as a viable base for accuracy to which routine methods for FT4 can be compared. 1. Van Houcke, S.K., et. al. Clin. Chem. Lab. Med. 2011, 49, 1275–1281.

Sleep telemedicine training in fellowship programs: a survey of program directors.

Telemedicine is a novel modality of health care delivery that can improve patients' access to sleep medicine services, but little is known about telemedicine training during sleep medicine fellowship. We studied telemedicine training prevalence, use, and attitudes of program directors (PDs) and other faculty members, PDs' receptiveness to a standardized telemedicine curriculum, and whether PDs have reviewed existing American Academy of Sleep Medicine (AASM) sleep telemedicine reference materials. This was an anonymous online survey of all 86 PDs of accredited sleep medicine fellowships in the United States. Response rate was 45%. Thirteen (33.3%) of the PDs already offer telemedicine experience to their trainees, although none use a standard telemedicine curriculum. Among the 26 (66.7%) PDs not offering telemedicine experience, 38.5% plan to do so and 53.9% agree that it would benefit fellows. Most PDs (57.9%) report faculty using telemedicine now or within the next 3 years. Many PDs agree that telemedicine is technically feasible, but relatively few agree it is financially feasible (82.1% and 38%, respectively). Few PDs have reviewed both primary AASM telemedicine reference materials. Overall, 64.1% of PDs agree that a national sleep telemedicine curriculum could be useful. Although only a minority of current sleep medicine fellows are exposed to telemedicine, it is likely that most will get some exposure in the next 3 years. PDs' attitudes toward telemedicine vary significantly with respect to feasibility and importance to their programs. Nevertheless, most PDs believe a standardized sleep telemedicine training curriculum could be useful.

LA-ICP-MS U[sbnd]Pb geochronology of wolframite by combining NIST series and common lead-bearing MTM as the primary reference material:Implications for metallogenesis of South China

Direct dating of W and WSn deposits by wolframite is more reliable relatively to gangue mineral and important for understanding their timing and genesis. However, such analysis still lacks of homogeneous wolframite standard recently. Due to containing considerable and variable common lead, and inhomogeneous in different grains, the wolframite sample of MTM, which is a promising candidate reference material proposed by previous studies, is not suitable as a primary standard for wolframite UPb dating by LA-ICP-MS using the normal normalization method as zircons. In this contribution, a modified normalization method is established for wolframite UPb dating, in which NIST612 or 614 and MTM are used for correction of PbPb and UPb ratios, respectively. Wolframite UPb dating are performed on the Langcun, Xihuashan, Piaotang, Shamai W or WSn deposits and the Baiganhu ore district, the obtained lower intercept 206Pb/238U ages are comparable with the ages from syngenetic molybdenite, cassiterite, muscovite and the genetically related granites, as well as wolframite by water vapor-assisted ns-LA-ICP-MS UPb dating method. The results of this analysis demonstrate that the robust age for W mineralization can be determined by LA-ICP-MS UPb dating of wolframite using this modified calibration method. Mineralization ages of 125–130 Ma by directly dating of metal minerals for the Langcun W, Jianfengpo Sn and large-size Xianglushan W deposits confirm that there exists an important WSn mineralization event in this period. The close temporal and spatial correlation indicates the granites and W-Cu-Mo-Pb-Zn-Sn mineralization have a genetic relationship with each other and are resulted from the same tectonic-magmatic-hydrothermal events during 140 to 120 Ma in South China.

Standardizing units of measurement for medicinal biomarkers across healthcare systems and countries

Background: In the field of laboratory medicine, the terms "standardization" and "harmonization" are often used interchangeably, as they both aim to achieve the same outcome: ensuring that measurement results from different routine measurement procedures are equivalent over time and space, in accordance with specific analytical and clinical quality requirements. However, these phrases delineate two separate but interconnected ideas grounded on the principles of traceability. Aim of Work: The aim of this review is to clarify the distinction between the concepts of standardization and harmonization in laboratory medicine, and to highlight the importance of these efforts in improving patient care. Methods: This review synthesizes the existing literature on the concepts of standardization and harmonization in laboratory medicine, their underlying principles, and their practical applications. Results: The term "standardization" refers to the process of ensuring that measurement results are comparable and can be traced back to the International System of Units (SI) using a high-quality primary reference material and/or a reference measurement method (RMP). The term "harmonization" is often used when there are no high-level main reference materials or reference measurement procedures available, but the results obtained are nonetheless comparable.

An isotope dilution LC–MS/MS-based candidate reference method for the quantification of androstenedione in human serum and plasma

The accurate measurement of androstenedione in human serum and plasma is required for steroid profiling to assure the appropriate diagnosis and differential diagnosis of hyperandrogenism. In this work, we introduce an isotope dilution liquid chromatography–tandem mass spectrometry (LC–MS/MS) candidate reference measurement procedure for the quantification of androstenedione in human serum and plasma. The performance of the procedure enables its use in the evaluation and standardization of routine assays and for the evaluation of patient samples to ensure the traceability of individual patient results. As the primary standard, a certified reference material from NMIA (National Measurement Institute, Australia) was used. Additionally, a quantitative nuclear magnetic resonance (qNMR) method was developed for the value assignment of the primary reference material, which ensures the direct traceability to SI units, as well as the independence from the availability of reference materials. 13C3-labeled androstenedione was used as the internal standard. The introduced method allows the measurement of androstenedione in the range of 0.05–12 ng/mL, and the assay imprecision was found to be <2% between 5 and 12 ng/mL, 3.5% at 1.5 ng/mL, and 5.2% at 0.05 ng/mL, with an accuracy of 95–105% for the serum and 91–103% for the plasma matrix. The transferability to a second laboratory was validated by method comparison based on 112 patient samples. The comparison of the results obtained from the presented method and an LC–MS/MS routine assay, using 150 native patient samples, showed a good correlation with a bias of the routine method of ≤4.0%.

High‐Precision, High‐Accuracy Oxygen Isotope Measurements of Zircon Reference Materials with the SHRIMP‐SI

Analytical protocols for SHRIMP‐SI oxygen isotope analysis (δ18O) of a suite of zircon reference materials (RMs) are presented. Data reduction involved a robust estimate of uncertainties associated with the individual spot as well as for groups where the spot data are combined. The repeatability of δ18O measurements is dependent on both the analytical conditions and the choice of the primary reference material. Under optimised conditions, repeatability was often better than 0.4‰ (2s) allowing sample uncertainties to be obtained to better than 0.2‰ (at 95% confidence limit). Single spot uncertainty combined the within‐spot precision with the scatter associated with repeated measurements of the primary zircon reference material during a measurement session. The uncertainty for individual spots measured under optimised conditions was between 0.3 and 0.4‰ (at 95% confidence). The analytical protocols described were used to assess a variety of zircon RMs that have been used for geochronology and for which laser fluorination oxygen isotope data are available (Temora 2, FC1, R33, QGNG and Plešovice), as well as zircons that have been used as RMs for trace element or other types of determination (Mud Tank, Monastery, 91500, AS57, AS3, KIM‐5, OG1, SL13, CZ3 and several other Sri Lankan zircons). Repeated analyses over nine sessions and seven different mounts show agreement within analytical uncertainty for Temora 2, FC1, R33, QGNG, Plešovice and 91500, when normalised to Mud Tank. For existing ion microprobe mounts with these materials, an appropriate δ18O can be determined. However, care should be taken when using zircons from the Duluth Complex (i.e., FC1, AS57 and AS3) as reference materials as our data indicated an excess scatter on δ18O values associated with low‐U zircon grains.

Zea maize reference materials for genetically modified organism detection in Mexico.

Zea maize reference materials for genetically modified organism detection in Mexico.

Megacircones ediacáricos de la sienita nefelínica de San José del Guaviare y su potencial como material de referencia para datación U/Pb mediante LA-ICP-MS

With the aim of expanding the reference materials of the Geochronology Laboratory of the Colombian&nbsp;Geological Survey (LG-SGC, in Spanish), zircons were collected from the nepheline syenite of&nbsp;San José del Guaviare, Jordán locality (Colombia). The SNG-1 sample was composed of 24 zircons&nbsp;selected from the fraction between 2 and 5 millimeters long, which were mounted and polished in&nbsp;an epoxy resin block. The zircons were dated by analyzing the isotopic ratios of uranium and lead&nbsp;using the LA-ICPMS method. In the LG-SGC, 92 points on the zircons were selected for analysis,&nbsp;and at the University of Rennes in France (LG-URF), 24 points from crystals found nearby were&nbsp;selected for analysis from a previous cathodoluminescence study. Concordant ages for the zircons&nbsp;for both laboratories corresponded to a crystallization age of 608 ± 1.2 Ma and 602 ± 3 Ma,&nbsp;respectively, which differ by less than 1% despite the difference in instrumentation and analytical&nbsp;procedures. For systematic error correction and quality control, international reference material,&nbsp;such as Plešovice, GJ-1, FC-5 Duluth and Mount Dromedary zircon, was used. The uncertainties&nbsp;generated during the analyses are similar (1.2 and 3.2 Ma), and the mean square-weighted deviation (MSWD) of the concordia diagrams was &lt; 1 in both cases, indicating low dispersion of the&nbsp;results. Some discordant ages show that the U/Pb ratios are not uniform, as expected for a primary&nbsp;reference material. However, we believe that the zircons of the Jordán syenite have potential use as&nbsp;a secondary reference material for the LG-SGC provided they are carefully selected and prepared,&nbsp;their geochemical content (including rare earth elements, REE) is characterized, and quality monitoring&nbsp;of U/Pb dating is performed, as these zircons are large, reaching up to 4 cm, abundant, and&nbsp;possible to collect in the Colombian territory.

Modeling the Measurement: Δ47, Corrections, and Absolute Ratios for Reference Materials

AbstractClumped isotope studies on CO2, Δ47, that is the excess in the isotopologue containing both 13C and 18O at mass 47, can be very useful since they can give temperature estimates independent of the bulk isotopic composition. The measurement itself can be affected by a number of items. Here we develop a data processing model to examine the effects different interferences might have on the final calculated value. It incorporates known issues, for example, pressure baseline, 17O excess, and shifts in absolute ratios for primary reference materials and parameters used for 17O correction. We also included linearity effects as well as differences in isotopologue absolute abundances at a given m/z. What normally would be considered acceptable mass spectrometer 45R and 46R linearity can skew Δ47 results. That is 0.04‰/V and −0.04‰/V linearity on 45R and 46R respectively would also cause an apparent shift in the parameters used for 17O corrections. Measurements were made on CO2(g) equilibrated with water, and we were able to match up the effects seen with model results. Linearity and small differences in amplitude between sample and working reference gas affected Δ47 determination, as did apparent shifts in isotopologue abundances under different conditions. This may (partially) account for discrepancies seen in Δ47‐temperature calibrations curves between laboratories. We also developed an easy way to precisely calculate the δ13C and δ18O that works well in spreadsheets without the need for multiple iterations.

Alternative Methods for Determination of Certified Value and its Uncertainty: Case Study of Using the Gravimetric Method for Preparation of Gaseous Primary Reference Material of Ethanol in Nitrogen at the Slovak Institute of Metrology

Gaseous mixtures of ethanol in nitrogen are prepared by the gravimetric method according to ISO 6142. The liquid component, ethanol, is added into the cylinder by the gas tight syringe. The exact amount of added liquid is determined by weighing the syringes. The exact amount of ethanol is calculated before starting filling the cylinder in accordance with the concentration of the final mixture. This calculated amount of liquid is filled into the syringe. The same type and volume of the empty syringe is used as a reference syringe. Before filling, the full syringe is weighed vs. the reference syringe. After filling, the empty syringe is weighed vs. the reference syringe. This procedure and the determination of the uncertainty of the weighing have a considerable influence on the certified value of the final mixture. Here, based on this simple experiment, we present the approach for uncertainty analysis used at the Slovak Institute of Metrology and compare it with different approaches, which includes the GUM uncertainty framework, the Monte Carlo method, and the characteristic function approach.

Natural Titanite Reference Materials forIn SituU‐Pb and Sm‐Nd Isotopic Measurements byLA‐(MC)‐ICP‐MS

Titanite is a common accessory mineral that preferentially incorporates considerable amounts of U and light rare earth elements in its structure, making it a versatile mineral forin situU‐Pb dating and Sm‐Nd isotopic measurement. Here, we presentin situU‐Pb ages and Sm‐Nd isotope measurement results for four well‐known titanite reference materials (Khan,BLR‐1,OLT1 andMKED1) and eight titanite crystals that could be considered potential reference material candidates (Ontario,YQ‐82, T3, T4,TLS‐36,NW‐IOA, Pakistan and C253), with ages ranging from ~ 20 Ma to ~ 1840 Ma. Results indicate thatBLR‐1,OLT1, Ontario,MKED1 and T3 titanite have relatively homogeneous Sm‐Nd isotopes and low common Pb and thus can serve as primary reference materials for U‐Pb and Sm‐Nd microanalysis.YQ‐82 and T4 titanite can be used as secondary reference materials forin situU‐Pb analysis because of their low common Pb. However, internal structures and mineral inclusions inYQ‐82 will require careful selection of suitable target domains. Pakistan titanite is almost concordant with an age of 21 Ma and can be used as a reference material when dating Cenozoic titanite samples.

Analytical Validation of a Highly Sensitive, Multiplexed Chronic Myeloid Leukemia Monitoring System Targeting BCR-ABL1 RNA

This study describes the analytical performance of the QuantideX qPCR BCR-ABL IS Kit, the first Food and Drug Administration–cleared assay designed to monitor breakpoint cluster region–Abelson tyrosine-protein kinase 1 (BCR-ABL1) fusion transcripts isolated from peripheral blood specimens from patients with chronic myeloid leukemia. This multiplex real-time quantitative RT-PCR assay amplifies both e13a2 and e14a2 Major BCR-ABL1 transcripts and the reference target ABL1. The test results are provided in international scale (IS) values by incorporating armored RNA-based calibrators that have defined IS values tied directly to the World Health Organization BCR-ABL1 Primary Reference Materials, without the necessity of determining and maintaining conversion factors. For each batch run, the integrated interpretive software evaluates run and specimen quality control metrics (including a sufficient amount of ABL1 control transcripts to ensure a minimal limit of detection) and calculates both molecular response (MR) and %IS values for each specimen. The test has a limit of detection of MR4.7 (0.002%IS) and a linear range from MR0.3 (50%IS) to MR4.7 (0.002%IS) for both Major transcripts. Single-site and multisite precision studies demonstrated a maximum SD of 0.13 MR (30% CV within the assay range between MR0.7 and MR3.7). The performance of this BCR-ABL1 monitoring test meets all of the clinical guideline recommendations for sensitivity and IS reporting for the management of chronic myeloid leukemia patients.

MON-602 Improving The Accuracy And Reliability Of Free Thyroxine Measurements Through The CDC Clinical Standardization Programs

Reliable free thyroxine (FT4) measurements are essential for assessing thyroid function and properly diagnosing and treating thyroid disorders. Although FT4 measurements are used extensively in research and clinical practice, the accuracy and reliability of current methods prevent correct detection, treatment, and prevention of thyroid disorders in patient care, making standardization of FT4 measurements a priority. Currently, there are no serum-based reference materials commercially available for FT4. CDC Clinical Standardization Programs (CDC CSP) is working with the Committee for Standardization of Thyroid Function Tests (C-STFT) of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and the Partnership for the Accurate Testing for Hormones (PATH) to address these issues through development of an accurate and sensitive higher-order Reference Measurement Procedure (RMP) for FT4. The CDC Clinical Reference Laboratory has developed a FT4 method using a modified equilibrium dialysis procedure. 1 FT4 in serum was isolated from the binding proteins in 1 mL equilibrium dialysis cells for 4 hours at 37oC. Dialysates were spiked with internal standard (thyroxine-13C6) and further isolated with extractions prior to injection on a liquid chromatography tandem mass spectrometry (LC-MS/MS) instrument. Bracketed calibration and primary reference materials were used to determine the concentration of FT4 in serum. Chromatographic separation was achieved using a C18 reverse phase column with a gradient of water and acetonitrile with addition of 0.1% formic acid. Quantification by selective reaction monitoring (SRM) analysis was performed in the positive ion mode using electrospray ionization (ESI). Two transitions were monitored for each analyte and internal standard, and triplicate injections were used to minimize any instrument instability. The proposed RMP has been evaluated and optimized for precision, accuracy, and sensitivity. The within-day and between-day imprecision are 2.5-2.9% and 0.9-1.3%, respectively. By comparisons with the Reference Laboratory at the University of Ghent, the proposed CDC RMP reported a bias within +1.0%. Factors affecting measurement accuracy were investigated and steps were taken to maximize recovery for optimum performance of the method. FT4 was detectable in all samples and thus suitable for analysis of hypo-, eu-, and hyperthyroid patients. To ensure accurate values are reported for FT4, careful consideration is needed for all steps of sample preparation and analysis. This candidate reference method for FT4 in serum demonstrates good accuracy and precision, and as such this method can be used as a viable base for accuracy to which routine methods for FT4 can be compared. 1. Van Houcke, S.K., et. al. Clin. Chem. Lab. Med. 2011, 49, 1275-1281.

Recommendations for reporting ion mobility Mass Spectrometry measurements.

Here we present a guide to ion mobility mass spectrometry experiments, which covers both linear and nonlinear methods: what is measured, how the measurements are done, and how to report the results, including the uncertainties of mobility and collision cross section values. The guide aims to clarify some possibly confusing concepts, and the reporting recommendations should help researchers, authors and reviewers to contribute comprehensive reports, so that the ion mobility data can be reused more confidently. Starting from the concept of the definition of the measurand, we emphasize that (i) mobility values (K 0) depend intrinsically on ion structure, the nature of the bath gas, temperature, and E/N; (ii) ion mobility does not measure molecular surfaces directly, but collision cross section (CCS) values are derived from mobility values using a physical model; (iii) methods relying on calibration are empirical (and thus may provide method‐dependent results) only if the gas nature, temperature or E/N cannot match those of the primary method. Our analysis highlights the urgency of a community effort toward establishing primary standards and reference materials for ion mobility, and provides recommendations to do so. © 2019 The Authors. Mass Spectrometry Reviews Published by Wiley Periodicals, Inc.

Evaluation of gas mixture components dosing using the gravimetric method for preparation of primary reference material of ethanol in nitrogen

Evaluation of gas mixture components dosing using the gravimetric method for preparation of primary reference material of ethanol in nitrogen

Evaluation of gas mixture components dosing using the gravimetric method for preparation of primary reference material of ethanol in nitrogen

Evaluation of gas mixture components dosing using the gravimetric method for preparation of primary reference material of ethanol in nitrogen

The importance of cylinder passivation for preparation and long-term stability of multicomponent monoterpene primary reference materials

Abstract. Monoterpenes play an important role in atmospheric chemistry due to their large anthropogenic and biogenic emission sources and high chemical reactivity. As a consequence, measurements are required to assess how changes in emissions of monoterpenes impact air quality. Accurate and comparable measurements of monoterpenes in indoor and outdoor environments require gaseous primary reference materials (PRMs) that are traceable to the international system of units (SI). PRMs of monoterpenes are challenging to produce due to the high chemical reactivity and low vapour pressures of monoterpenes and also their propensity to convert into other compounds, including other terpenes. In this paper, the long-term stability of gravimetrically prepared static monoterpene PRMs produced in differently passivated cylinders, including sampling canisters, was assessed. We demonstrate that static PRMs of multiple monoterpenes can be prepared and used as a suitable long-term standard. For the first time the effect of cylinder pressure and decanting from one cylinder to another on the chemical composition and amount fraction of monoterpenes was also studied. Gravimetrically prepared PRMs of limonene in high pressure cylinders were compared to a novel portable dynamic reference gas generator based on dilution of pure limonene vapour emitted from a permeation tube.

Provisional standardization of hepcidin assays: creating a traceability chain with a primary reference material, candidate reference method and a commutable secondary reference material.

Background Hepcidin concentrations measured by various methods differ considerably, complicating interpretation. Here, a previously identified plasma-based candidate secondary reference material (csRM) was modified into a serum-based two-leveled sRM. We validated its functionality to increase the equivalence between methods for international standardization. Methods We applied technical procedures developed by the International Consortium for Harmonization of Clinical Laboratory Results. The sRM, consisting of lyophilized serum with cryolyoprotectant, appeared commutable among nine different measurement procedures using 16 native human serum samples in a first round robin (RR1). Harmonization potential of the sRM was simulated in RR1 and evaluated in practice in RR2 among 11 measurement procedures using three native human plasma samples. Comprehensive purity analysis of a candidate primary RM (cpRM) was performed by state of the art procedures. The sRM was value assigned with an isotope dilution mass spectrometry-based candidate reference method calibrated using the certified pRM. Results The inter-assay CV without harmonization was 42.1% and 52.8% in RR1 and RR2, respectively. In RR1, simulation of harmonization with sRM resulted in an inter-assay CV of 11.0%, whereas in RR2 calibration with the material resulted in an inter-assay CV of 19.1%. Both the sRM and pRM passed international homogeneity criteria and showed long-term stability. We assigned values to the low (0.95±0.11 nmol/L) and middle concentration (3.75±0.17 nmol/L) calibrators of the sRM. Conclusions Standardization of hepcidin is possible with our sRM, which value is assigned by a pRM. We propose the implementation of this material as an international calibrator for hepcidin.

Urinary proteins: up-to-date reference methods for urinary protein analysis.

Measurement of urine albumin has been introduced in the new classification of kidney disease (KD) as a marker for detecting, monitoring and predicting KD. Currently, the measure is not standardized. The variability of results obtained with commercially available procedures is important and can lead to misclassification of patients. Analytical standardization, started in 2007, is in progress. SRM 2925 primary reference material, SRM 3666 secondary reference material and liquid chromatography isotope dilution mass spectroscopy (LC-IDMS) reference measurement procedure are being validated by the National Institute of Standards and Technology (NIST). This report presents strategies and difficulties for developing this reference system.

Setting up a service for a faecal immunochemical test for haemoglobin (FIT): a review of considerations, challenges and constraints

Quantitative faecal immunochemical tests for haemoglobin (FIT) have now been advocated by the National Institute for Care and Health Excellence (NICE: DG30) to assist in the triage of patients presenting...