bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanomechanics of wild-type and mutant dimers of the inner-ear tip-link protein protocadherin 15
Authors: Villasante Camila M. , Deng Xinyue , Cohen Joel E. , Hudspeth A. J.
Published: October 2024

Mechanical force controls the opening and closing of mechanosensitive ion channels atop the hair bundles of the inner ear. The filamentous tip link connecting transduction channels to the tallest neighboring stereocilium modulates the force transmitted to the channels and thus changes their probability of opening. Each tip link comprises four molecules: a dimer of protocadherin 15 (PCDH15) and a dimer of cadherin 23, all of which are stabilized by Ca
2+
binding. Using a high-speed optical trap to examine dimeric PCDH15, we find that the protein’s mechanical properties are sensitive to Ca
2+
and that the molecule exhibits limited unfolding at a physiological Ca
2+
concentration. PCDH15 can therefore modulate its stiffness without undergoing large unfolding events under physiological conditions. The experimentally determined stiffness of PCDH15 accords with published values for the stiffness of the gating spring, the mechanical element that controls the opening of mechanotransduction channels. When PCDH15 exhibits a point mutation, V507D, associated with nonsyndromic hearing loss, unfolding events occur more frequently under tension and refolding events occur less often than for the wild-type protein. Our results suggest that the maintenance of appropriate tension in the gating spring is critical to the appropriate transmission of force to transduction channels, and hence to hearing.
Autonomous multicolor bioluminescence imaging in bacteria, mammalian, and plant hosts
Authors: Kusuma Subhan Hadi , Kakizuka Taishi , Hattori Mitsuru , Nagai Takeharu
Published: October 2024

Bioluminescence imaging has become a valuable tool in biological research, offering several advantages over fluorescence-based techniques, including the absence of phototoxicity and photobleaching, along with a higher signal-to-noise ratio. Common bioluminescence imaging methods often require the addition of an external chemical substrate (luciferin), which can result in a decrease in luminescence intensity over time and limit prolonged observations. Since the bacterial bioluminescence system is genetically encoded for luciferase-luciferin production, it enables autonomous bioluminescence (auto-bioluminescence) imaging. However, its application to multiple reporters is restricted due to a limited range of color variants. Here, we report five-color auto-bioluminescence system named Nano-lanternX (NLX), which can be expressed in bacterial, mammalian, and plant hosts, thereby enabling auto-bioluminescence in various living organisms. Utilizing spectral unmixing, we achieved the successful observation of multicolor auto-bioluminescence, enabling detailed single-cell imaging across both bacterial and mammalian cells. We have also expanded the applications of the NLX system, such as multiplexed auto-bioluminescence imaging for gene expression, protein localization, and dynamics of biomolecules within living mammalian cells.
Complexity of confined water vitrification and its glass transition temperature
Authors: Melillo Jorge H. , Cangialosi Daniele , Di Lisio Valerio , Steinrücken Elisa , Vogel Michael , Cerveny Silvina
Published: October 2024

The ability of vitrification when crossing the glass transition temperature (T
g
) of confined and bulk water is crucial for myriad phenomena in diverse fields, ranging from the cryopreservation of organs and food to the development of cryoenzymatic reactions, frost damage to buildings, and atmospheric water. However, determining water’s T
g
remains a major challenge. Here, we elucidate the glass transition of water by analyzing the calorimetric behavior of nano-confined water across various pore topologies (diameters: 0.3 to 2.5 nm). Our approach involves subjecting confined water to annealing protocols to identify the temperature and time evolution of nonequilibrium glass kinetics. Furthermore, we complement this calorimetric approach with the dynamics of confined water, as seen by broadband dielectric spectroscopy and linear calorimetric measurements, including the fast scanning technique. This study demonstrated that confined water undergoes a glass transition in the temperature range of 170 to 200 K, depending on the confinement size and the interaction with the confinement walls. Moreover, we also show that the thermal event observed at ~136 K must be interpreted as an annealing prepeak, also referred to as the “shadow glass transition.” Calorimetric measurements also allow the detection of a specific heat step above 200 K, which is insensitive to annealing and, thereby, interpreted as a true thermodynamic transition. Finally, by connecting our results to bulk water behavior, we offer a comprehensive understanding of confined water vitrification with potential implications for numerous applications.
YkuR functions as a protein deacetylase in
Streptococcus mutans
Authors: Ma Qizhao , Li Jing , Yu Shuxing , Zhou Jing , Liu Yaqi , Wang Xinyue , Ye Dingwei , Wu Yumeng , Gong Tao , Zhang Qiong , Wang Lingyun , Zou Jing , Li Yuqing
Published: October 2024

Protein acetylation is a common and reversible posttranslational modification tightly governed by protein acetyltransferases and deacetylases crucial for various biological processes in both eukaryotes and prokaryotes. Although recent studies have characterized many acetyltransferases in diverse bacterial species, only a few protein deacetylases have been identified in prokaryotes, perhaps in part due to their limited sequence homology. In this study, we identified YkuR, encoded by
smu_318
, as a unique protein deacetylase in
Streptococcus mutans
. Through protein acetylome analysis, we demonstrated that the deletion of
ykuR
significantly upregulated protein acetylation levels, affecting key enzymes in translation processes and metabolic pathways, including starch and sucrose metabolism, glycolysis/gluconeogenesis, and biofilm formation. In particular, YkuR modulated extracellular polysaccharide synthesis and biofilm formation through the direct deacetylation of glucosyltransferases (Gtfs) in the presence of NAD
+
. Intriguingly, YkuR can be acetylated in a nonenzymatic manner, which then negatively regulated its deacetylase activity, suggesting the presence of a self-regulatory mechanism. Moreover, in vivo studies further demonstrated that the deletion of
ykuR
attenuated the cariogenicity of
S. mutans
in the rat caries model, substantiating its involvement in the pathogenesis of dental caries. Therefore, our study revealed a unique regulatory mechanism mediated by YkuR through protein deacetylation that regulates the physiology and pathogenicity of
S. mutans
.
Ultrafast transient absorption spectra and kinetics of human blue cone visual pigment at room temperature
Authors: Krishnamoorthi Arjun , Salom David , Wu Arum , Palczewski Krzysztof , Rentzepis Peter M.
Published: October 2024

The ultrafast photochemical reaction mechanism, transient spectra, and transition kinetics of the human blue cone visual pigment have been recorded at room temperature. Ultrafast time-resolved absorption spectroscopy revealed the progressive formation and decay of several metastable photo-intermediates, corresponding to the Batho to Meta-II photo-intermediates previously observed with bovine rhodopsin and human green cone opsin, on the picosecond to millisecond timescales following pulsed excitation. The experimental data reveal several interesting similarities and differences between the photobleaching sequences of bovine rhodopsin, human green cone opsin, and human blue cone opsin. While Meta-II formation kinetics are comparable between bovine rhodopsin and blue cone opsin, the transition kinetics of earlier photo-intermediates and qualitative characteristics of the Meta-I to Meta-II transition are more similar for blue cone opsin and green cone opsin. Additionally, the blue cone photo-intermediate spectra exhibit a high degree of overlap with uniquely small spectral shifts. The observed variation in Meta-II formation kinetics between rod and cone visual pigments is explained based on key structural differences.
Chemical mapping of the surface interactome of PIEZO1 identifies CADM1 as a modulator of channel inactivation
Authors: Koster Anna K. , Yarishkin Oleg , Dubin Adrienne E. , Kefauver Jennifer M. , Pak Ryan A. , Cravatt Benjamin F. , Patapoutian Ardem
Published: October 2024

The propeller-shaped blades of the PIEZO1 and PIEZO2 ion channels partition into the plasma membrane and respond to indentation or stretching of the lipid bilayer, thus converting mechanical forces into signals that can be interpreted by cells, in the form of calcium flux and changes in membrane potential. While PIEZO channels participate in diverse physiological processes, from sensing the shear stress of blood flow in the vasculature to detecting touch through mechanoreceptors in the skin, the molecular details that enable these mechanosensors to tune their responses over a vast dynamic range of forces remain largely uncharacterized. To survey the molecular landscape surrounding PIEZO channels at the cell surface, we employed a mass spectrometry-based proteomic approach to capture and identify extracellularly exposed proteins in the vicinity of PIEZO1. This PIEZO1-proximal interactome was enriched in surface proteins localized to cell junctions and signaling hubs within the plasma membrane. Functional screening of these interaction candidates by calcium imaging and electrophysiology in an overexpression system identified the adhesion molecule CADM1/SynCAM that slows the inactivation kinetics of PIEZO1 with little effect on PIEZO2. Conversely, we found that CADM1 knockdown accelerates inactivation of endogenous PIEZO1 in Neuro-2a cells. Systematic deletion of CADM1 domains indicates that the transmembrane region is critical for the observed effects on PIEZO1, suggesting that modulation of inactivation is mediated by interactions in or near the lipid bilayer.
Estimate of in-band eddy current effect in space gravitational wave detection
Authors: Xu Jia-Hao , Zhang Li-Na , Ke Jun , Li Cheng-Zong , Ma Wen-Long
Published: October 2024

In space detection of gravitational waves (GWs), the presence of a low-frequency varying magnetic field will generate eddy currents in the test mass, resulting in a varying magnetic moment. This magnetic moment will couple with a constant magnetic field gradient, producing residual acceleration within the frequency band of GW detection, causing the test mass to deviate from the free-falling mode. However, this effect has not yet been studied clearly in the noise budget for TianQin and LISA Pathfinder since the constant DC magnetic susceptibility was applied to quantify the varying magnetic moment. This paper utilizes the parameter of alternating current magnetic susceptibility to define this process, and further analyzes and evaluates the effect. In a general magnetic field environment, the contribution of this effect to TianQin acceleration noise reaches 20% from 0.1 mHz to 3 mHz. The contribution to LISA noise is less than 10% from 10−4 to 0.1 Hz, and less than 10% below 10−4 Hz. This effect does not have a potential limit on LISA low-frequency science down to 20 µHz (Armano et al 2018 Phys. Rev. Lett.
120 061101).
Black holes, Achilles and the original tortoise coordinate
Authors: Pössel Markus
Published: October 2024

The ‘frozen star’ picture of black holes, based on the fact that an outside observer will never see a collapsing sphere shrink sufficiently to form a black hole horizon, was a historical obstacle to the understanding of black holes, and continues to be a stumbling point for students trying to understand horizons. Promoting the discrete steps in Zeno's original story of Achilles and the tortoise to a ‘Zeno time coordinate’ provides a quantitative toy model that allows students to understand why the ‘frozen star’ phenomenon does not mean that objects cannot fall into a black hole. The toy model can be used for teaching about this particular feature of black holes in an introductory setting that does not introduce the Schwarzschild metric and its tortoise coordinates.
Non-uniform dynamic magnetic field compensation for a lightweight magnetically shielded room based on distributed differential coils
Authors: Zhao Jiye , Liu Jiawen , Zhou jiqiang , Zhang Lu , Sun Jinji
Published: October 2024

Due to the influence of material characteristics and engineering imperfections, the residual magnetic fields including static and dynamic field in a lightweight magnetically shielded room (MSR) present non-uniform distribution characteristic. To effectively reduce the residual static field, a non-uniform field compensation method based on distributed coils has been proposed. This method takes the L2-norm of the magnetic field at the target array points as the objective function, to optimize the compensation current in each of the designed distributed coils, achieving non-uniform field compensation. To further achieve compensation for non-uniform residual dynamic field, a closed-loop control system containing a voltage divider and multi-channel amplifiers is designed in this paper. Additionally, the coil constant of the distributed differential coils and the initial magnetic field distribution vector for dynamic compensation are redefined. In conjunction with a PI controller, dynamic compensation is achieved using a single optically pumped magnetometer as the feedback component. The experimental results indicate that the average dynamic field decreased from 376.75 pT to 27.80 pT over the central volume of (300 mm)3 in MSR, achieving a near-zero magnetic environment. This method has universal applicability for compensating non-uniform residual field under different working conditions.
High-temperature transport properties of a two-dimensional weakly doped parabolic semiconductor
Authors: Rukelj Zoran , Radić Danko , Grbić Mihael S , Kupčić Ivan
Published: October 2024

A version of the Mexican-hat Hamiltonian is used to study high-temperature transport properties of a two-dimensional weakly doped semiconductor with electron–hole symmetric bands. For a finite doping level and a temperature-dependent band-gap, we find a closed analytical form of the temperature-dependent chemical potential. The effective concentrations of charge carriers participating in transport coefficients are analyzed in the space spanned by the total electron concentration and temperature. It is shown that these concentrations are the sum of a residual contribution and two thermally activated contributions, with a complicated dependence on temperature. The analytical expression for the Hall coefficient

R
H

is also found. It is argued that it is a non-monotonic function of the doping level with the maximum at the doping

n
max

that is a linear function of temperature at high enough temperatures. The analysis of the real part of the interband conductivity shows that it is inversely proportional to incoming photon energy at low temperatures and that it is nearly constant over a wide energy range at high temperatures. These results are expected to be of significant importance in understanding transport and optical properties of weakly doped two-dimensional semiconductors with nearly symmetric parabolic bands.
SODD-YOLOv8: an insulator defect detection algorithm based on feature enhancement and variable row convolution
Authors: Jianxing Wang , Yuli Lu , Bisheng Wei , Gangjin Huang , Jinmei Guo
Published: October 2024

To address the detection challenges in defective images of insulators in transmission lines, including tiny object size, significant scale variations, a wide variety of defects, and complex background interference. In this study, an improved insulator defect detection algorithm is proposed, based on the YOLOv8s framework and combining feature enhancement and deformable convolution techniques. Firstly, to address the image feature distortion problem caused by aerial photography, a deformable convolutional feature extraction module (DCFEM) is introduced, which is designed to enhance the model’s ability to adapt to the local geometric deformation, so as to effectively recover the distorted feature information in the image. Moreover, to enhance the detection ability of the model for small objects, a small object feature enhancement module is designed, which adopts an efficient multi-scale attention mechanism, and aims to enhance the feature extraction ability of small objects, improve the sensitivity to small-size defects, and improve the detection accuracy. Eventually, to optimize the computational efficiency of the model, the average pooling-sparse convolution-batch normalization (BN) module is proposed. This module combines average pooling, sparse convolution and BN techniques to achieve a lightweight model while maintaining a high level of feature extraction capability. Experimental results on the China power line insulator dataset show that the improved model achieves a 4.3 percentage point improvement in the mAP metric compared to YOLOv8s, and the number of parameters in the model is reduced by 10%. The proposed scheme not only improves the accuracy and efficiency of defect detection, but also reduces the demand for computational resources, thus providing a more reliable and efficient solution for insulator defect detection in practical applications.
Soil moisture estimation in the unsaturated zone using surface wave measurements and hybrid modeling framework
Authors: Song Homin , Kook Woo Dong
Published: October 2024

Soil moisture plays a critical role in influencing various facets of ecosystem dynamics. The preference for measuring soil moisture without physical intrusion has been desirable for precise assessments while minimizing disruptions to soil structural, hydraulic, and biological characteristics. In this study, we explored the potential of surface elastic waves as a proxy to estimate soil moisture profiles to a depth of 1.05 m at intervals of 0.1 m. We conducted a multichannel analysis of surface waves (MASW) survey and measured soil moisture at depths of 0.15 m and 0.35 m. To address the limited availability of soil moisture measurements, we developed a mechanistic soil moisture model as a substitute for measured soil moisture profiles. Our results showed that as soil moisture increased, the propagation of surface waves became more pronounced due to reduced frictional resistance. However, it was not straightforward to link measured surface wave responses and subsurface soil moisture profile. To address these challenges, we developed a convolutional neural network (CNN) with the inputs of the frequency-velocity and frequency-wavenumber images obtained from the measured surface waves. We found that the integration of MASW and CNN proved effective in estimating soil moisture profiles to a depth of 1.05 m at intervals of 0.1 m without causing disturbances to the soil (MAE = 0.0035 m3 m−3). This study suggested that the combined use of surface waves and CNN hold promise in measuring soil moisture profiles without physical disruptions. As such, the proposed approach could serve as a viable alternative to noninvasive soil moisture sensors.
X-ray coronary angiography background subtraction by adaptive weighted total variation regularized online RPCA
Authors: Shakeri Saeid , Almasganj Farshad
Published: October 2024

Objective. X-ray coronary angiograms (XCA) are widely used in diagnosing and treating cardiovascular diseases. Various structures with independent motion patterns in the background of XCA images and limitations in the dose of injected contrast agent have resulted in low-contrast XCA images. Background subtraction methods have been developed to enhance the visibility and contrast of coronary vessels in XCA sequences, consequently reducing the requirement for excessive contrast agent injections. Approach. The current study proposes an adaptive weighted total variation regularized online RPCA (WTV-ORPCA) method, which is a low-rank and sparse subspaces decomposition approach to subtract the background of XCA sequences. In the proposed method, the images undergo initial preprocessing using morphological operators to eliminate large-scale background structures and achieve image homogenization. Subsequently, the decomposition algorithm decomposes the preprocessed images into background and foreground subspaces. This step applies an adaptive weighted TV constraint to the foreground subspace to ensure the spatial coherency of the finally extracted coronary vessel images. Main results. To evaluate the effectiveness of the proposed background subtraction method, some qualitative and quantitative experiments are conducted on two clinical and synthetic low-contrast XCA datasets containing videos from 21 patients. The obtained results are compared with six state-of-the-art methods employing three different assessment criteria. By applying the proposed method to the clinical dataset, the mean values of the global contrast-to-noise ratio, local contrast-to-noise ratio, structural similarity index, and reconstruction error (RE) are obtained as

5.976

,

3.173

,

0.987

, and

0.026

, respectively. These criteria over the low-contrast synthetic dataset were

4.851

,

2.942

,

0.958

, and

0.034

, respectively. Significance. The findings demonstrate the superiority of the proposed method in improving the contrast and visibility of coronary vessels, preserving the integrity of the vessel structure, and minimizing REs without imposing excessive computational complexity.
Zinc oxide-based sensor prepared by modified sol–gel route for detection of low concentrations of ethanol, methanol, acetone, and formaldehyde
Authors: Dhahri Ramzi , Benamara Majdi , Nassar Kais Iben , Elkenany Elkenany Brens , Al-Syadi A M
Published: October 2024

We successfully synthesized zinc oxide (ZnO) nanoparticles using the sol–gel method, followed by their application onto alumina substrates for sensor testing. Comprehensive characterization of the nanomaterials was carried out utilizing XRD, SEM, TEM, UV–VIS-IR, and Photoluminescence (PL) techniques. The nanoparticles displayed a hexagonal wurtzite crystal structure, typical of ZnO. UV–Vis-IR spectroscopy revealed significant absorption in the UV region, with the band gap energy calculated to be 3.22 eV. PL spectra indicated the presence of various defects, such as oxygen vacancies and zinc interstitials, within the ZnO structure. SEM analysis of the deposited film surface showed spherical agglomerates, confirming the nanoscale dimensions, while energy-dispersive x-ray spectroscopy spectra affirmed the high purity of the ZnO films, rich in Zn and O elements. Sensor tests demonstrated the ZnO sensor’s high sensitivity to low concentrations of volatile organic compounds such as ethanol, formaldehyde, methanol, and acetone. Notably, at an operational temperature of 300 °C, the sensor exhibited a remarkable response to 5 ppm of each gas, with the following response and response/recovery times: for methanol, 11.47 and 36 s/57 s; for acetone, 11.54 and 25 s/52 s; for formaldehyde, 0.79 and 53 s/58 s; and for ethanol, 3.88 and 9 s/59 s.
Scheme of preparing cluster states with cat qubits
Authors: Zhu Fan , Yu Ke-hui , Han Yu-xiang , Xue Jiao-jiao , Li Hong-rong
Published: October 2024

Cluster states are essential quantum resources for one-way quantum computations and quantum networks. The reliable generation of cluster states in specific quantum systems is crucial for initializing complex quantum operations. In this paper, we introduce an efficient scheme for the deterministic preparation of a cluster state via circuit quantum electrodynamics (QED). Our scheme involves four individual microwave resonators, each of which is coupled to a superconducting transmon qutrit. We demonstrated that a four-cqubit cluster state can be achieved using three controlled-phase gate operations. The cluster state is prepared deterministically, eliminating the need for measurement-based feedback. Throughout these operations, the qutrit remains in its ground state, effectively minimizing decoherence from the qutrit. Numerical simulations suggest that our scheme can generate high-fidelity cluster states using current-circuit QED technology. We believe that our model will facilitate exploration of future large-scale continuous-variable quantum information processing systems.
Corrigendum: Assessing the Tidal Influences on the Coastal Erosion-Accretion Processes in the Indian Sundarban Delta using Hydrodynamic Models and Geoinformatics (2023 IOP Conf. Ser.: Earth Environ. Sci. 1164 012002)
Authors: Bhui K , Bhadra T , Samanta S , Hazra S
Published: October 2024

Please see Article PDF for corrigendum text.
Introduction
Authors: Brady Henry E
Published: October 2024

Given human foibles and the difficulties of aggregating preferences, political theorists have been understandably concerned with whether democratic deliberation and the representation of individuals by delegates can produce democratic outcomes. Yet by focusing on these topics, they have neglected the American Founding Fathers’ concern with faction, and they have failed to understand and set standards for the vigorous competition among political parties, interest groups, and the media that is at the core of modern representative democracies. Because of this neglect, political theorists have missed a chance to do for politics what economists have done for economics through their detailed study of market failures and competitive successes within economic systems. In this book, Charles Beitz rectifies this mistake by considering the operation of the entire political system. He sets standards for political competition and uses empirical political science findings to determine when those standards are met or violated. The result moves us beyond a focus on deliberation by asking when representative systems work For the People? and when they fail to do so.
Unrepresentative Democracy in America
Authors: Karlan Pamela S
Published: October 2024

Fair and effective representation requires at least some measure of majoritarianism, but the United States falls systemically short of that ideal in two important structural respects. First, in the foreseeable future a majority of the US Senate is likely to be controlled by states in which a minority of Americans live—states that differ systematically along several dimensions from the states in which the majority lives. Second, in presidential elections, the way the Electoral College operates means that the winner of the popular vote may not be elected president—creating an “electoral inversion.” For both the Senate and the presidency, there is a serious risk to majoritarian control. Moreover, this countermajoritarian skew has become self-reenforcing after a series of Supreme Court that have further undercut democracy.
Reply to Commentators
Authors: Beitz Charles R
Published: October 2024

The commentators provide illuminating remarks on the relationship between preferences and policy and political competition, on the importance of legitimacy, and on the shortcomings of American institutions such as the Senate and Electoral College. Gilens offers a shorthand for thinking about three justifying purposes for democracy (responsiveness, protecting group interests, and decisiveness), and his empirical finding that the rich are much more likely to get their way than the middle class or poor suggests a failure of democracy linked to inequality. Mansbridge adds a concern with democratic legitimacy and asks whether competition could undermine it and how competition might be moderated. Karlan shows that a combination of the rules of the American Constitution and changes in political geography have exacerbated the countermajoritarian features of the Senate and Electoral College. I comment on the ways these themes enrich and qualify the main lines of argument in the lectures.
A-002 Analytical Validation of the Zybio High Sensitivity Cardiac Troponin I CLIA Assay
Authors: Ma T , Tang D , Wu X , Deng K
Published: October 2024

Background

High-sensitivity cardiac troponin (hs-cTn) plays a pivotal role in the early diagnosis of Acute Coronary Syndrome (ACS). With technological advancements, the sensitivity of troponin assays has significantly improved. The International Federation of Clinical Chemistry (IFCC) criteria for hs-cTn assays include a total imprecision (Coefficient of Variation, CV) ≤10% at the gender-specific 99th percentile value and detectable levels in ≥50% of a healthy population. This study aims to evaluate the performance of Zybio's hs-cTnI assay against these high-sensitivity standards

Methods

This study involved 1661 individuals undergoing routine health checks at Chongqing Medical University Third Hospital. Exclusion criteria included recent medication use, abnormal NT-proBNP levels, significant cardiac silhouette changes in chest X-rays, age <20, incomplete data, pregnancy, or history of severe chronic diseases. Participants were classified into apparent healthy and healthy groups based on blood pressure, lipid profiles, and electrocardiogram results. Laboratory examinations included hs-cTn and NT-ProBNP concentrations using Zybio's chemiluminescence instrument EXI2400 and associated reagent kits, with other parameters measured using standard biochemical and high-performance liquid chromatography methods.

Results

Of the 1247 participants (556 males, 691 females) included in the final analysis, 1157 showed detectable hs-cTnI levels above the limit of detection (LOD), yielding an overall detection rate of 92.78%. Detection rates were 93.71% in males and 92.04% in females. The total imprecision (CV) of hs-cTnI at gender-specific 99th percentile values over 20 days was below 10%, meeting the high-sensitivity criteria. This finding was consistent across lower and higher concentration ranges.

Conclusions

The Zybio hs-cTnI assay demonstrated a high detection rate in a healthy population, with 92.78% detectability overall, 93.71% in males, and 92.04% in females. The assay met the high-sensitivity criteria of IFCC, with a total imprecision (CV) of less than 10% at the gender-specific 99th percentile levels. These results validate the utility of Zybio's hs-cTnI assay for clinical application in the early diagnosis of ACS.
A-020 Evaluation of the QuidelOrtho Diagnostics Vitros NT-proBNP II Assay
Authors: Leung E K , Tsan J , Xiao Y
Published: October 2024

Background

N-terminal-proBNP (NT-proBNP), a short peptide originating from the cleavage of proBNP by Corin, can be used as a diagnostic test in individuals presenting with signs and symptoms consistent with heart failure (HF). QuidelOrtho Diagnostics released its latest reformulation of its NT-proBNP assay, the Vitros NT-proBNP II assay. The analytical performance of this assay was evaluated.

Methods

Repeatability, reproducibility, and carryover were assessed using quality control material. The analytical measuring range and clinical reportable range (AMR and CRR) were assessed using commercially available material and diluted patient samples. Accuracy was assessed by comparing results from the Vitros NT-proBNP II assay and results from the Vitros NT-proBNP assay. Instrument-to-instrument comparison was performed by comparing results from the NT-proBNP II assay from two different Vitros 5600 chemistry analyzers. Paired heparin and EDTA plasma samples were assessed for specimen type comparison.

Results

Repeatability and reproducibility were <=10% CV and no carryover was observed. The AMR was 20 - 30,000 pg/mL and the CRR extended the range to 600,000 pg/mL. Passing-Bablok analysis showed a significant proportional bias with a slope of 1.34 for samples up to 12,000 pg/mL (Vitros NT-proBNP). Vendor-performed comparison studies showed no significant proportional bias with a slope of 1.06 using unweighted Deming analysis for samples up to 20,700 pg/mL (Vitros NT-proBNP). Instrument-to-instrument and heparin-to-EDTA plasma comparisons showed no significant biases.

Conclusions

The NTproBNP II assay showed acceptable repeatability, reproducibility, and no carryover. The AMR analysis verified the measuring range in the IFU of the assay and the CRR is extended to 600,000 pg/mL. Results were very comparable between two different Vitros 5600s and between paired heparin and EDTA plasma specimens. Comparison between the Vitros NT-proBNP and Vitros NT-proBNP II assays showed a very significant proportional bias (slope of 1.34) for specimens up to 12,000 pg/mL measured on the Vitros NT-proBNP assay, but the proportional bias is less significant at higher NT-proBNP values (>20,000 pg/mL, Vitros NT-proBNP) are included in the analysis. There may be a significant matrix effect or interference at lower NT-proBNP concentrations with the reformulated reagent, which may be less prominent when NT-proBNP is present at much higher concentrations.
A-038 Interlaboratory Comparison of Parathyroid Hormone Analytical Results Across Clinical Assays from 8 Manufacturers - Steps Towards Standardization
Authors: Lee G S , Lyle A , Ribera A , Behm K E , Lagoueyte C , Sugahara O , Buchannan T , Long L , Collins L , Vesper H W
Published: October 2024

Background

Parathyroid hormone (PTH) is an 84 amino acid peptide produced by the parathyroid gland and is a key biomarker used for the diagnosis and treatment of Chronic Kidney Disease-Mineral and Bone Disorder, as well as hypo- and hyperparathyroidism. PTH clinical assays were previously reported to exhibit significant inter-assay measurement variability, which limits the utility of PTH as a diagnostic biomarker and can result in the misclassification of patients. Thus, there is a need for PTH clinical assay standardization to improve clinical assay measurement agreement. The Centers for Disease Control and Prevention’s Clinical Standardization Program (CDC-CSP) will launch a PTH standardization program, which is in support of and coordinated with the IFCC Committee on Bone Metabolism. In preparation, the CDC-CSP conducted an Inter-Laboratory Comparison Study to evaluate the current status of PTH inter-assay variability and to investigate potential sources of variability.

Methods

Eight PTH assay manufacturer’s laboratories measured PTH in 42 deidentified, fresh-frozen single donor serum samples in duplicate over 2 independent runs. Sample PTH concentrations ranged from 1.3 - 324 pg/mL, based on initial screening values. Five manufacturers submitted data for 2 different assays, resulting in PTH measurements from 13 assays total. Data were submitted to the CDC CSP for analysis.

Results

Assay precision was <5% for 10/13 measurement procedures (MP) assessed and 3 MPs exhibited precisions between 5 - 18%. Assay-specific PTH measurements demonstrated good linear correlation compared to the all-assay mean concentration. Interestingly, inter-assay variability increased with increasing PTH concentrations, with individual sample standard deviations increasing from 2.9 - 123, with a mean SD of 24.1 and individual sample CVs increasing from 18.9 - 44.5%, with a mean CV of 24.2%.

Conclusions

This study provides new insights into PTH inter-assay variability and assay performance for assays commonly used in the clinical setting. The findings of this PTH Interlaboratory Comparison Study establish a baseline for PTH inter-assay variability and will guide future PTH standardization efforts.
A-041 Metoclopramide Stimulation Test can Rule Out Prolactinoma in Patients with Moderate Hyperprolactinemia
Authors: González Á , Moreno A , Deza S , Salvador J , Galofre J C , Alegre E
Published: October 2024

Background

Prolactinoma is the main cause of hyperprolactinemia once physiological and pharmacological causes are excluded. Prolactin (PRL) and thyrotropin (TSH) response to dopaminergic antagonists has been previously used in prolactinoma diagnosis. Current guidelines only recommend baseline PRL concentration in diagnosis, considering values exceeding 250 ng/mL highly suggestive of prolactinoma. However, subtler hyperprolactinemia is much more frequent, and magnetic resonance imaging (MRI) studies are necessary to detect potential prolactinomas. Our aim was to examine the utility of a metoclopramide (MCP) stimulation test as a screening tool to evaluate the need for pituitary MRI studies in patients with moderate hyperprolactinemia.

Methods

We retrospectively selected 67 moderate hyperprolactinemia patients (<250 ng/mL), with a MCP test and a pituitary MRI within the same assistance. We excluded patients with pharmacological treatments affecting dopaminergic axis. According MRI results we classified them in patients with microadenoma (<10 mm; n=23), with macroadenoma (≥10 mm; n=5) or without adenoma (n=39). Maximum relative increases over baseline concentrations were calculated for PRL (ΔPRLMax) and TSH (ΔTSHMax). The Research Ethic Committee approved the study.

Results

ΔPRLMax exceeds baseline PRL capability to identify patients with an adenoma (AUC=0.8718 vs 0.7756). ΔPRLMax below 220% identifies 100% of these patients with 71% of specificity (Table 1).

Screening with MCP test would have avoided 42% of MRI, resulting in 34% costs saving. Analysis of TSH response only slightly increased the specificity when considered as a secondary criterion. Test length can be reduced from 60 to 30 minutes without losing screening capability.

Conclusions

A shortened MCP test is a useful and cost-effective screening tool to avoid unnecessary MRI. Its simplicity allows its performance in almost any clinical facility, allowing to easily rule out prolactinoma in an important percentage of patients, something of upmost importance specially in regions were MRI facilities are scarce.
A-050 Reference Intervals for Plasma Concentrations of C-Terminal Telopeptide of Type-I Collagen (CTX) for Greek Adult Population
Authors: Makris K , Trifonidi I , Tournis S , Chronopoulos E
Published: October 2024

Background

CTX assays measure a fragment of the C-terminal telopeptide of type I collagen released during resorption of mature bone. To adequately interpret CTX results, method-specific and population specific reference intervals are needed. We aimed to determine reference intervals for plasma concentrations of CTX.

Methods

We collected samples from 431 apparently healthy Greeks (140 men as well as 150 pre- and 139 postmenopausal women), who volunteered to participate in our study. Data on socio-demographic characteristics, medical histories and medications were collected and subjects with conditions or receiving medications that affecting bone metabolism were excluded. Dual-energy x-ray absorptiometry (DXA) used to measure bone mineral density (BMD) in all participants. All blood collections were performed in the morning after overnight fast. Plasma EDTA samples were used for the measurement of CTX. Measurements were performed by an automated chemiluminescent immunoassay on the Maglumi-X3 analyzer (Snibe, Shenzhen, China). The reference interval was defined as the central 95% range and determined according to CLSI guide C28-A3 using the MedCalc Software.

Results

The table summarizes our results. The mean age of men, pre- and post-menopausal women were 50.7, 40,7 and 58.4 years respectively. DXA results revealed that 348 participants had normal BMD, 74 HAD osteopenia and 9 had osteoporosis which excluded from analysis. Since our data were not normally distributed (Shapiro-Wilk test) in any group and after the exclusion of outliers (Tukey test), we used the non-parametric method suggested by the CLSI guide to determine the reference intervals. Multiple regression analysis also revealed that sex menopausal status and BMD were factors affecting CTX values.

Conclusions

We provide reference intervals for the determination of CTX concentrations in EDTA-plasma for the Greek adult population using an automated immunoassay. Our data may aid to interpret bone turnover in the Greek adult population.
A-052 Clinical usefulness of ADAMS A1c HA-8190V automatic switching mode for the HbA1c measurement in Hb variants
Authors: Yun Y , Lee Y , Seo J
Published: October 2024

Background

High-performance liquid chromatography (HPLC) is widely used as a HbA1c routine assay. However, quantification of glycated hemoglobin (HbA1c) is a challenge in patients with hemoglobin (Hb) variants. In this study, we evaluated the clinical utility and analytical performance of new developed ARKRAY ADMAS HA-8190V assay using autoswitch mode, that automatically switches between variant and fast mode depending on patient Hb characteristics, in patients with Hb variant suspected in Korea.

Methods

The measuring time for HbA1c assay was compared between the HA-8180V fast mode (existing model) and the autoswitch mode of HA-8190V (new model) in 60 normal Hb samples. And the HbA1c measured values was compared bewteen the HA-8180V fast mode and the HA-8190V autoswitch mode in 30 low Hb samples. In addition, flag detection for the abnormal Hb and measured values for 21 Hb variant samples were analyzed using the HA-8180V fast mode and the HA-8190V autoswitch mode.

Results

It took 50.8 minutes and 39.1 minute to measure 60 normal Hb samples by HA-8180V fast mode and HA-8190V autoswitching mode, respectively. The values could not be measured at the HA-8180V fast mode for 7 of 30 low Hb samples, whereas all samples could be measured at HA-8190V autoswitching mode. For 21 Hb variant samples, HA-8180V fast mode showed abnormal flag detections for only 14 samples, but HA-8190V autoswitch mode reported abnormal variant flags for 20 samples. In the result accuracy evaluation (% difference) based on capillary electrophoresis HbA1c assay (Sebia, Lisses, France) in the 21 Hb variant samples, the % difference of HA-8190 V autoswitch mode was 3.9%, which was superior to HA-8180V fast mode of -11.65%.

Conclusions

Autoswitch mode of The HA-8190V (automatically switch between variant and fast mode based on patient Hb characteristics) showed more accurate flag detection and HbA1c measurements in patients with Hb variants, along with shorter test time and manual reduction.
A-070 Evaluation of Plain and Serum-Separator Blood Collection Tubes for the Measurement of Steroid Hormones by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Authors: Garg U , Ramoo B , Frazee C , Dasgupta A
Published: October 2024

Background

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) is the preferred method for quantifying steroids. Commonly measured steroids 11-deoxycortisol, androstenedione, testosterone, 17-hydroxyprogesterone and dehydroepiandrosterone (DHEA). Although serum separator blood collection tubes may not be recommended but their frequent use is attributed to the ease of serum separation. Moreover, the serum separator tube may be the only available option for analysis, without the need for additional sample collection. Under such conditions, from certain serum separator tubes, we observed occasional interference in LC-MS/MS steroid method. We pursued to evaluate the performance of blood collection tubes without and those with serum separators, for the quantification of specified steroids by LC-MS/MS.

Methods

Blood samples were collected from 10 volunteers using both plain and serum separator blood collection tubes procured from two major suppliers (Greiner and BD). The specified steroids were measured by LC-MS/MS method. The procedure involved addition of labeled internal standards to the samples and extraction of steroids in methyl tert-butyl ether. Subsequently, the extract dried under a stream of nitrogen, and the residue was reconstituted in the mobile phase. LC-MS/MS analysis involved multiple reaction monitoring (MRM) for the specified steroids and their internal standards.

Results

The figure shows a sample chromatogram from a subject with blood samples collected in a plain (A) and serum separator tubes from Greiner (B) and BD (C1 and C2, a zoomed of C1). In this sample, from the plain tube, the concentrations of 11-deoxycortisol, androstenedione, testosterone, 17-hydroxyprogesterone and DHEA were 27, 55, 690, 99 and 283 ng/mL respectively. No significant interference was observed in Greiner serum separator tube. Whereas BD serum separator tube exhibited several erroneous peaks making the quantitation of several steroids challenging or inaccurate.

Conclusions

In the described LC-MS/MS method, BD serum-separator tubes exhibited erroneous peaks. These peaks were not seen in Greiner serum-separator tubes.
A-077 Evaluation of Diagnostic Thresholds for Adrenal Insufficiency Post-Cosyntropin Stimulation: Assessment Using Siemens Atellica Cortisol Immunoassay
Authors: Li S , Chen L , Calanche A T , Lee J K , Ghalib L , Meng Q H
Published: October 2024

Background

Accurate interpretation of the cosyntropin (adrenocorticotropic hormone [ACTH]) stimulation test relies on method- and assay-specific cortisol cutoffs. While the Endocrine Society recommends an 18 ug/dL cutoff, lower thresholds (14.6 ug/dL) were proposed for the Roche Elecsys II assay in 2021, which employs a monoclonal antibody. However, cutoff values for the new Siemens Atellica platform, utilizing polyclonal antibody-based cortisol assays, remain undetermined. This study aimed to evaluate cortisol thresholds specific to the Siemens Atellica immunoassay by comparing cortisol measurements with the Roche Elecsys II assay.

Methods

The ACTH stimulation test was conducted in patients with suspected adrenal insufficiency (n=28). Serum cortisol levels were measured using the Siemens Atellica and Roche Elecsys II assays. Atellica assay results were also compared with those obtained via liquid chromatography tandem mass spectrometry (LC-MS/MS).

Results

Cortisol concentrations measured with the Atellica assay exhibited approximately 25-30% higher bias compared to LC-MS/MS and the Roche Elecsys II assay. Passing Bablok regression analysis revealed a strong correlation between the Atellica and LC-MS/MS assays (R2 = 0.9312, slope = 1.26, intercept = 0.34). However, the correlation between Atellica and the Roche Elecsys II assay was weaker compared to LC-MS/MS (R2 = 0.7049 at 0 min, slope = 1.28, intercept = 0.19; R2 = 0.8066 at 30 min, slope = 1.28, intercept = 0.59; R2 = 0.8584 at 60 min, slope = 1.17, intercept = 2.03). The optimized cortisol threshold using the Atellica assay was determined to be 18 ug/dL at 30 minutes after stimulation (sensitivity, 100%; specificity, 90%), using the proposed 14.6 ug/dL cutoff at 30 minutes on Roche Elecsys II as the standard.

Conclusions

Employing assay-specific cutoffs is crucial for reducing misclassification and overtreatment in patients with suspected adrenal insufficiency. We recommend a cortisol threshold of 18 ug/dL at 30 minutes after ACTH stimulation for the Atellica assay, consistent with the Endocrine Society's recommendation.