Discover the most talked about and latest scientific content & concepts.

Concept: Standard


BACKGROUND: Despite considerable global investigation over several decades, the roles of vitamin D in health and disease development remains convoluted. One recognised issue is the difficulty of accurately measuring the active forms of vitamin D. Advances made include some new methods addressing the potential interference by excluding epimers and isobars. However, there is no evidence that epimers are without function. Therefore, the aim of this study was to develop and validate, for the first time, a new assay to simultaneously measure levels of 6 forms of vitamin D along with two epimers. The assay was applied to multilevel certified reference material calibrators and 25 pooled human sera samples obtained from the Vitamin D External Quality Assessment Scheme (DEQAS) to demonstrate its efficiency. RESULTS: The assay is capable of simultaneously measuring 8 vitamin D analogues over the calibration ranges and LODs (in nmol/L) of: 1alpha25(OH)2D2 [0.015-1; 0.01], 1alpha25(OH)2D3 [0.1-100; 0.01], 25OHD3 [0.5-100, 0.025], 3-epi-25OHD3 [0.1-100, 0.05], 25OHD2 [0.5-100, 0.025], 3-epi-25OHD2 [0.1-100, 0.05], vitamin D3 [0.5-100, 0.05] and vitamin D2 [0.5-100, 0.05], using stanozolol-d3 as internal standard. Certified reference material calibrators and external quality control samples (DEQAS) were analysed to meet the standards outlined by National Institute of Standards and Technology (NIST). Validation steps included recovery and both precision and accuracy under inter- and intra-day variation limit of detection, and analysis of each analyte over a linear range. All validation parameters were in line with acceptable Food and Drug Administration (FDA) guidelines and the standards of the National Institute of Standards and Technology (NIST). All eight analogues were quantified with the 25OHD levels being commensurate with DEQAS data. CONCLUSIONS: This report details the application of a new LC-MS/MS based assay for the efficient analysis of eight analogues of vitamin D over a range of samples, which is a significant advance over the existing methods. Simultaneous measure of 8 vitamin D analogues does not compromise the analytical capability of the assay to quantify the commonly used biomarker (25OHD) for vitamin D status. The results demonstrate the feasibility of applying the assay in research and clinical practice that i) excludes misleading measures owing to epimers and isobars and ii) is able to quantify the excluded component to facilitate further in vivo investigation into the roles of ubiquitous epimers.

Concepts: Vitamin D, Mass spectrometry, Measurement, Validation, Analytical chemistry, Standard, Calibration, Certified reference materials


Thus far, validated whole blood assays used in in vitro fibrinolysis experiments using thromboelastometry (ROTEM) are lacking or have yet to be tested in humans. The objective was first, to establish a standardized modified ROTEM approach to detect both hypo- and hyperfibrinolysis. And second, to perform a technical and clinical validation of the assay.

Concepts: Coagulation, Fibrinolysis, Assay, Standard, Fibrinolytic system, Thromboelastometry


To investigate effects on rat testes of radiofrequency radiation emitted from indoor Wi-Fi Internet access devices using 802.11.g wireless standards.

Concepts: Standard, Internet, Bluetooth, Wi-Fi


While minimalist running shoes may have an influence on running biomechanics and on the incidence of overuse injuries, the term “minimalist” is currently used without standardisation. The objectives of this study were to reach a consensus on a standard definition of minimalist running shoes, and to develop and validate a rating scale that could be used to determine the degree of minimalism of running shoes, the Minimalist Index (MI).

Concepts: Standard, 2006 albums, Minimalism


The current standard practice of lung lesion diagnosis often leads to inconclusive results, requiring additional diagnostic follow up procedures that are invasive and often unnecessary due to the high benign rate in such lesions (Chest 143:e78S-e92, 2013). The Percepta bronchial genomic classifier was developed and clinically validated to provide more accurate classification of lung nodules and lesions that are inconclusive by bronchoscopy, using bronchial brushing specimens (N Engl J Med 373:243-51, 2015, BMC Med Genomics 8:18, 2015). The analytical performance of the Percepta test is reported here.

Concepts: Solitary pulmonary nodule, Standard, Lesion


The majority of adults in the U.S. now have state-legal access to medical or recreational cannabis products, despite their federal prohibition. Given the wide array of pharmacologically active compounds in these products, it is essential that their biochemical profile is measured and reported to consumers, which requires accurate laboratory testing. However, no universal standards for laboratory testing protocols currently exist, and there is controversy as to whether all reported results are legitimate. To investigate these concerns, we analyzed a publicly available seed-to-sale traceability dataset from Washington state containing measurements of the cannabinoid content of legal cannabis products from state-certified laboratories. Consistent with previous work, we found that commercial Cannabis strains fall into three broad chemotypes defined by the THC:CBD ratio. Moreover, we documented systematic differences in the cannabinoid content reported by different laboratories, relative stability in cannabinoid levels of commercial flower and concentrates over time, and differences between popular commercial strains. Importantly, interlab differences in cannabinoid reporting persisted even after controlling for plausible confounds. Our results underscore the need for standardized laboratory methodologies in the legal cannabis industry and provide a framework for quantitatively assessing laboratory quality.

Concepts: United States, Measurement, Chemistry, Cannabis, Standard, Washington, Recreational drug use, Laboratories



A Bayesian inference method for refining crystallographic structures is presented. The distribution of model parameters is stochastically sampled using Markov chain Monte Carlo. Posterior probability distributions are constructed for all model parameters to properly quantify uncertainty by appropriately modeling the heteroskedasticity and correlation of the error structure. The proposed method is demonstrated by analyzing a National Institute of Standards and Technology silicon standard reference material. The results obtained by Bayesian inference are compared with those determined by Rietveld refinement. Posterior probability distributions of model parameters provide both estimates and uncertainties. The new method better estimates the true uncertainties in the model as compared to the Rietveld method.

Concepts: Scientific method, Crystallography, Monte Carlo, Powder diffraction, Standard, Neutron diffraction, Bayes' theorem, Rietveld refinement


A sensitive and reliable method was developed for the determination of volatile components emitted from cut tobacco processing using thermal desorption (TD) followed by gas chromatography-mass spectrometry (GC-MS). In the work, to obtain the optimal sorbent, three commercial sorbents were compared in terms of adsorption efficiency. The carbotrap 349 was found to have the best performance. The desorption conditions were also studied. Validation of the TD-GC-MS method showed good sensibility, linearity and precision. Limits of detection ranges were from 0.20 to 3.6ng. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients relating to linearity were at least 0.9984. The analysis was reproducible, with relative standard deviation (n=8) within 6.5%. The target compound breakthrough examination showed no significant losses when about 1500ng standards were prepared. In order to evaluate the performance of the analytical method in the volatile constituents of cut tobacco, samples were taken in industrial areas of cut tobacco processing. Recoveries ranged from 85.1% to 110% for all the compounds and good precision had been reached (RSD<13.3). The results proved that TD-GC-MS was a simple, rapid and accurate method for the analysis of volatile compounds emitted from cut tobacco drying step.

Concepts: Scientific method, Mass spectrometry, Chemical compound, The Target, Standard deviation, Standard, Deviation, Volatile organic compound


Standardized Autism Diagnostic Observation Schedule (ADOS) scores provide a measure of autism severity that is less influenced by child characteristics than raw totals (Gotham et al. in Journal of Autism and Developmental Disorders, 39(5), 693-705 2009). However, these scores combine symptoms from the Social Affect (SA) and Restricted and Repetitive Behaviors (RRB) domains. Separate calibrations of each domain would provide a clearer picture of ASD dimensions. The current study separately calibrated raw totals from the ADOS SA and RRB domains. Standardized domain scores were less influenced by child characteristics than raw domain totals, thereby increasing their utility as indicators of Social-Communication and Repetitive Behavior severity. Calibrated domain scores should facilitate efforts to examine trajectories of ASD symptoms and links between neurobiological and behavioral dimensions.

Concepts: Psychology, Measurement, Metrology, Behavior, Human behavior, Standard, Behaviorism, Autism Diagnostic Observation Schedule