External Reproducibility Research Articles

Limited external reproducibility restricts the use of medical record review for benchmarking

BackgroundMedical record review (MRR) is used to assess the quality and safety in hospitals. It is increasingly used to compare institutions. Therefore, the external reproducibility should be high. In the...

The stable tungsten isotope composition of modern igneous reservoirs

Abstract Tungsten is a highly incompatible and fluid mobile element in the Earth’s crust and mantle, but its geochemical cycle in magmatic systems still remains poorly understood. Tungsten stable isotopes represent a novel tool with the potential to better constrain this cycle, because of possible W isotope fractionation during changes in redox-state (valence states +4 and +6) and coordination (tetrahedral and octahedral). By employing a 180W-183W double spike our analytical protocol for stable W isotope measurements yields an external reproducibility of ±0.018‰ (2 s.d.) in δ186/184W and enables the resolution of small scale stable W isotope variations between different igneous reservoirs. Here, we present the first stable W isotope data for representative volcanic rocks from different igneous settings including mid-ocean ridge basalts (MORBs), ocean island basalts (OIBs) and basalts to dacites from various subduction-related settings. The δ186/184W values of MORB samples from the Mid-Atlantic Ridge (+0.088 ± 0.017‰, n = 8) and OIB samples from the Canary Islands and Reunion Island (+0.084 ± 0.019; 2 s.d.; n = 17) show a narrow range and are analytically indistinguishable. This calls for a homogeneous stable W isotope composition in the mantle. Subduction-related rocks are more variable in their δ186/184W values (−0.009 to +0.195‰). Samples from the Troodos ophiolite complex in Cyprus show elevated W/Th and mainly high δ186/184W values (+0.101 to +0.195‰, n = 16) due to relative W enrichment from a subducted sediment component with heavy W isotope composition. In support of this model, Eastern Mediterranean sediments are isotopically heavier than mantle-derived rocks (+0.085 to +0.144‰ in δ186/184W, n = 5). Lavas from the Sunda arc show regional variability with a tendency towards lower δ186/184W values in the Central/East Java region (as low as −0.009‰). However, sediments from this region show uniformly high δ186/184W values of up to +0.301‰ and thus fail to explain the light compositions of the lavas. Hence, we rather propose that either the local subduction of an oceanic basement relief (Roo Rise) or source overprint by partial melts from deeply subducted crust accounts for low δ186/184W values in respective lavas. In arc settings, where the trace element budget is controlled by fluid-like components (New Britain) or melt-like components (Papua New Guinea) derived from shallowly subducted oceanic crust, we observe mantle-like W/Th and a narrow range in δ186/184W values (+0.109 ± 0.027‰, n = 19), which is only slightly elevated compared to MORBs and OIBs. This might hint towards the preferential release of isotopically heavy W during shallow fluid-induced melting events. Our results demonstrate that the stable W isotope composition of igneous rocks represents a novel tool to trace processes controlling the geochemical cycle of W in the silicate Earth.

Precise determination of radiogenic Sr and Nd isotopic ratios and Rb, Sr, Sm, Nd elemental concentrations in four coal ash and coal fly ash reference materials using isotope dilution thermal ionization mass spectrometry

Coal fly ash (CFA) and coal ash (CA) as a result of coal firing from power generation plants caused global environment contamination. It is important for environment science to monitor the migration and emission path of CFA and CA. Both radiogenic Sr and Nd isotope have proved to be powerful and sensitive tracers to address this issue. Unfortunately, up to now, high precision data of 87Sr/86Sr and 143Nd/144Nd isotope ratio for CFA and CA are rare to be reported. Hence, to boost up SrNd isotope application in environmental science, it is indispensible and urgent to report a suit of high precision data for SrNd isotope ratio and relative Rb, Sr, Sm and Nd element content for CFA and CA reference materials.In this work, we determined SrNd isotope ratios for four CFA and CF reference materials using thermal ionization mass spectrometry (TIMS). Reference values for these four CRMs (GBW08401, GBW11124, GBW11125d and JCFA-1) span a wide range in 87Sr/86Sr ratios from 0.705700 to 0.723650 and from 0.511950 to 0.512680 for 143Nd/144Nd. The external reproducibility (2 SD, n = 8) of four CRMs vary from 0.000014 to 0.000028 for 87Sr/86Sr and from 0.000008 to 0.000010 for 143Nd/144Nd. The concentrations of Rb, Sr, Sm and Nd elements of four CRMs were determined using ID-TIMS method. Considering all results, the reproducibility (1 RSD, n = 4) of elemental content was <0.6% for Rb and Sr, 0.4% ~1% for Sm and Nd. This indicates homogeneous distribution of Rb, Sr, Sm and Nd elements in these four CRMs. Hence, this suit of reference materials can be used for materials with different CFA and CA matrix composition for justification and quality control measures of radiogenic Sr and Nd isotope analyses. This study is the first to report the SrNd isotopic compositions of these CFA and CA reference materials.

Calcium isotope fractionation during magmatic processes in the upper mantle

Abstract The Earth’s mantle has a complex history of partial melting and melt-peridotite reaction that have redistributed Ca and other elements between residues and melting products. Given the considerable Ca isotopic variation reported in mantle rocks, evaluation of the fractionation of stable Ca isotopes in magmatic processes in the mantle is critical to decode mantle evolution and the effect of recycled materials. We have performed precise and accurate Ca isotopic analyses on a series of well-characterized spinel-facies mantle peridotites (lherzolite, harzburgite and dunite, n = 29), pyroxenites (websterite, clinopyroxenite and orthopyroxenite, n = 15) and their mineral constituents (n = 8) from the Balmuccia and Baldissero peridotite massifs of the Ivrea Zone in the Italian Alps. These peridotites underwent variable degrees of melting and melt-peridotite reaction, whereas the pyroxenites are mainly the products of melt-peridotite reaction and crystallization of migrating basic melts from the asthenosphere. The lherzolites from Balmuccia and Baldissero show δ44/40Ca values of 0.94 ± 0.11‰ (2sd, n = 22), which are uniform within long-term external reproducibility (±0.14‰, 2sd). The δ44/40Ca values of the harzburgites (0.83‰ to 0.92‰) do not differ from those of lherzolites, including those with a history of intensive melt-peridotite reaction to form replacive dunites. The websterites and spinel clinopyroxenites display δ44/40Ca of 0.86 ± 0.10‰ (n = 14), within the range of the lherzolites and harzburgites. The indistinguishable δ44/40Ca among these very diverse mantle rocks is the consequence of the overwhelming control of stable Ca isotopes by clinopyroxene in the magmatic processes involved, because clinopyroxene dominates the budget of Ca (>90% for harzburgites; 93% to 99% for lherzolites, websterites and clinopyroxenites). Only the clinopyroxene-poor ( 25% melting and replacive dunites tend to display slightly heavier Ca isotopic compositions. Consequently, irrespective of their magmatic history, most fertile mantle rocks from different geological settings display a homogenous Ca isotope composition, summarized as, δ44/40Ca of 0.94 ± 0.10‰ (2sd, n = 47) for the Earth’s mantle. The deviations in Ca isotopic variations observed in other mantle rocks may be attributed to kinetic isotope fractionation and metasomatism by melts with isotopic compositions influenced by recycled crustal materials.

High-precision measurement of B isotopes on low-boron oceanic volcanic rock samples via MC-ICPMS: Evaluating acid leaching effects on boron isotope compositions, and B isotopic variability in depleted oceanic basalts

Recent analytical advances have made the high precision (2SD, ±≤1‰) determination of boron (B) isotopic ratios in silicate rocks a possibility, but few such data are as yet available, especially for low B (<2 ppm) samples like oceanic basalts, where issues related to cryptic seawater alteration are a concern. This study carefully assesses the reproducibility of B isotope measurement via MC-ICPMS on silicate rocks. Based on repeated measurements of the standard reference materials B-5, B-6, JB-2, JR-2, AGV-2 and JB-3 and nature samples, the external reproducibility of MC-ICPMS measurements on the same solution is generally between 0.1‰ and 0.5‰ (2SD), a similar level of accuracy to that obtained based on long-term measurement of solution standard NIST SRM 951 of 0.4‰ (2SD). For different digestions, the average external reproducibility is 0.6‰ (2SD), which represents the whole procedure reproducibility, including chemical treatment. We have tested an acid leaching experimental procedure for its effects on the B isotope compositions of ~50 Ma boninites collected from a deep ocean setting. Fresh and moderately altered boninite samples were subjected to cold HCl leaching treatments for 1, 3, 5, 7 and 9 h, using 2 N and 6 N HCl, respectively. δ11B values for the fresh sample remained unchanged within error after leaching, suggesting that leaching did not lead to any B isotopic fractionation. δ11B values for different aliquots of an altered boninite sample show lower and uniform δ11B values after 1 h of 6 N HCl leaching, while aliquots leached in 2 N HCl show similar δ11B to the unleached altered sample. These results suggest that changes in B isotopes caused by at least moderate degrees of alteration, and/or adsorption effects in volcanic rocks preserved on the ocean floor can be effectively eliminated through short-duration 6 N HCl leaches before digestion and analysis. B isotope measurements on three documentably fresh, low-B N-type mid-ocean ridge basalt (MORB) glass samples from the Southwest Indian Ridge yield δ11B values from −6.62‰ to −7.39‰, within the range of the recommended global MORB value of ≈−7.1 ± 0.9‰, determined via SIMS methodologies (2SD at ±1.5‰; Marschall and Monteleone, 2015), and the range of four fresh glass samples from the Eastern Pacific Ridge of −7.3 ± 0.8‰, measured by in-situ laser-ablation ICP-MS (2SD at ±0.7–1.0‰; Le Roux et al., 2004).

Oxidative Stress Biomarkers as Prognostic Indicators of Severity in Patients With Dengue

There is evidence for the role of oxidative stress in severe dengue pathogenesis. However, previous observational studies presents certain methodological limitations, which may affect its internal and external validity. This study was a case-control analysis of patients with severe dengue and dengue with warning signs, to evaluate the serum protein carbonyls-PCOs and lipid hydroperoxides-LOOHs levels and activities of superoxide dismutases-SODs (MnSOD, Cu/ZnSOD and total SOD), as potential prognosis indicators of severity in dengue patients, using binary logistic regression analysis and strategy of double cross-validation. Therefore, the study population was subdivided into a derivation group (pediatric patients, Barranquilla-Colombia) and an external validation group (children and adults patients, National Institute of Health of Peru). PCOs was the only oxidative stress markers that showed a strongest association with the severity of dengue, both in children and adults. In the derivation group, the optimal cut-off point was estimated at 5.29 nmol/mg of protein, and in the external validation group, it was 5.77 nmol/mg of protein. The prognostic models based on these two diagnostic thresholds showed a high discriminatory capacity of dengue severity, external reproducibility, geographic transportability, and typical characteristics of diagnostic validity and safety of screening tests.

Clinical Utility of the Combined Positive Score for Programmed Death Ligand-1 Expression and the Approval of Pembrolizumab for Treatment of Gastric Cancer.

Regulatory approval of pembrolizumab for treatment of gastric and gastroesophageal junction (G/GEJ) adenocarcinoma required a reproducible scoring method for use of programmed death ligand-1 (PD-L1) protein expression as a companion diagnostic to identify likely responders to therapy. To develop an immunohistochemical scoring algorithm that includes PD-L1 expression for tumor and immune cells, that is, the combined positive score. Four previously treated tumor types in the KEYNOTE-012 and KEYNOTE-028 studies were analyzed descriptively with a version of the PD-L1 immunohistochemical 22C3 pharmDx assay labeled for investigational use only to determine the relative importance of PD-L1 expression in tumor versus immune cells as a biomarker for pembrolizumab response. A combined positive score was developed as a novel scoring method and was compared with the tumor proportion score in cohort 1 from the KEYNOTE-059 study (G/GEJ cancer). External reproducibility was assessed. Per combined positive score cutoff of 1 or more, the prevalence of PD-L1 expression in patients with G/GEJ cancer was 57.6% (148 of 257 patients), with reasonable enrichment of responses (odds ratio, 2.8). Per tumor proportion score cutoff of 1% or more, prevalence was 12.5% (32 of 257 patients), with minimal enrichment (odds ratio, 1.4). External reproducibility assessments demonstrated interpathologist overall agreement of 96.6% (591 of 612; 95% CI, 94.0%-98.7%) and intrapathologist overall agreement of 97.2% (595 of 612; 95% CI, 95.3%-98.9%). Combined positive score is a robust, reproducible PD-L1 scoring method that predicts response to pembrolizumab in patients with G/GEJ cancer. This novel scoring method supported US Food and Drug Administration approval of pembrolizumab as third-line therapy for G/GEJ cancer and has facilitated investigation in other indications.

Plasma Biomarkers for Colorectal Cancer Diagnosis Based on Metabolomics

Background: Metabolomics has been widely applied and has great potentialities in biomarkers identification for colorectal cancer (CRC). However, it turns out to be a hindrance by far for effective clinical translation owing to huge number and high inconsistency of biomarkers. Methods: We identified and verified differential plasma metabolites of CRC via a two-stage case-control metabolomics study in a population from Northeast China. Using receiver operating characteristic curve and pathway enrichment analyses, we selected biomarkers with favorable diagnostic efficiency and biological significance. We confirmed the tumor-specificity of these biomarkers by a metabolomics study of tumor-adjacent non-malignant paired tissue. Moreover, we conducted a systemic review of previous metabolomics studies in CRC to find biomarkers with external reproducibility in multiple populations. Results: We proposed three sets of candidate biomarkers of CRC with a particular focus on diagnostic efficiency, biological significance, tumor specificity, and external reproducibility. We showed that a five-biomarker panel of L-Tryptophan, 13-OxoODE, IDP, Glycochenodeoxycholate, and LysoPC(16:0) exhibited excellent diagnostic performance, favorable biological significance, and tumor specificity in our population. A six-biomarker panel of L−Phenylalanine, Linoleic acid, Citric acid, Inosine, Glycocholic acid, and LysoPC(14:0) showed the best extrapolation in diverse populations. Four metabolites (L-Tryptophan, Linoleic acid, Glycocholic acid, and LysoPC(16:0)) were ultimately recommended as the best combination with multiple advantages. Conclusion: We screened out the optimal panels of plasma biomarkers for CRC diagnosis and elucidated the potential usefulness of CRC metabolites under different requirements. Our proposed method may provide a powerful approach for metabolic biomarkers screening in other diseases. Funding Statement: This work was supported by grants from National Nature Science Foundation of China (81773503, 81573147, and 81473055), Scientific Research Foundation for the Returned Overseas Scholars of Heilongjiang Province (LC2018033), and Natural Science Foundation of Heilongjiang Province of China (for Youths, QC2018111). Declaration of Interests: All authors have declared that no conflict of interest exists. Ethics Approval Statement: We carried out this study after obtaining written informed consent from all the study subjects and approval from the Human Research and Ethics Committee of Harbin Medical University. All experiments including relevant details were performed in accordance with relevant guidelines and regulations.

Hg Compound-Specific Isotope Analysis at Ultratrace Levels Using an on Line Gas Chromatographic Preconcentration and Separation Strategy Coupled to Multicollector-Inductively Coupled Plasma Mass Spectrometry.

Stable Hg isotope analyses are nowadays widely employed to discriminate Hg sources and understand its biogeochemical cycle. Until now, total Hg isotopic compositions have been mainly used but Hg compound-specific isotopic analysis (CSIA) methodologies are emerging. Online Hg-CSIA were limited to samples containing high concentrations, but in this work we overcome this limitation for the measurement of inorganic (IHg) and monomethylmercury (MMHg) by gas chromatography hyphenated to multicollector-inductively coupled plasma mass spectrometry (GC/MC-ICPMS) through the use of an automated online preconcentration strategy, allowing injection volumes up to 100 times larger than usual. The preconcentration of Hg species and subsequent transfer to the column were achieved by a programmed temperature vaporization (PTV) injector fitted with a packed liner. The PTV parameters were first optimized using a quadrupole ICPMS, and then its suitability for Hg-CSIA was evaluated with long-term replicate analysis of various standards and reference materials (RMs). The large preconcentration capability enables analyses with Hg concentrations in the organic solvent 2 orders of magnitude lower than the previous conventional GC/MC-ICPMS method, but a compound specific standard bracketing procedure was required for MMHg in order to correct for the differential behavior of Hg species in the liner. The external reproducibility of the method ranged from 0.19 to 0.39 ‰ for Δ199Hg and δ202Hg (as 2 SD, n = 143-167) depending on the species. The analysis of various RMs demonstrated the applicability to environmental samples with species concentrations down to about 150 ng g-1. This new methodology opens the way for a much wider range of online Hg-CSIA measurements that will improve our understanding of the Hg biogeochemical cycle.

Determination of Sm‐Nd Isotopic Compositions in Fifteen Geological Materials Using Laser Ablation MC‐ICP‐MS and Application to Monazite Geochronology of Metasedimentary Rock in the North China Craton

In this study, we report both 143Nd/144Nd and 147Sm/144Nd values in twelve minerals (apatite, titanite, monazite and eudialyte) based on analyses over 4 years using LA‐MC‐ICP‐MS. The positive correlation between the measured βSm and βNd (r2 = 0.9981) over this time in our laboratory demonstrates the excellent long‐term stability of the method. Compared with the normal method, Sm and Nd signal intensities were improved by a factor of 2.9 with the use of X skimmer and Jet sample cones in combination with the addition of nitrogen at 3–6 ml min−1 to the central gas flow. The enhancement of signal intensity benefits the accurate in situ determination of the Sm‐Nd isotopes of samples poor in these elements. 143Nd/144Nd values were also determined in two manganese nodules and GSMC Co‐rich crust with low mass fractions of Nd (94–293 μg g−1). Generally, most of the obtained Sm‐Nd isotopic compositions in these geological materials are consistent with published values. ‘External reproducibility’ (2s) of 143Nd/144Nd and 147Sm/144Nd was typically better than 0.06‰ and 2.5‰, respectively, demonstrating that the Durango, Otter Lake, NW‐1 and MAD apatites, the Khan, and OLT‐1 titanites, MGMH#117531 monazite and LV01 eudialyte are promising candidate reference materials for in situ Sm‐Nd isotopic determinations. The Trebilcock, Mae Klang and 44069 monazites are only suitable for in situ Nd isotopic determinations because of their heterogeneous Sm/Nd compositions. The heterogeneous Sm‐Nd composition of titanite BLR‐1 demonstrates that it is not a suitable reference material for in situ Sm‐Nd isotopic determinations. Deep‐sea samples (NOD‐A‐1 and NOD‐P‐1 manganese nodule, GSMC Co‐rich crust) with low mass fractions of Nd also show homogenous Nd isotopic compositions. Sm‐Nd isotopic ratios of a monazite (MQG‐22) from the North China Craton were measured as a case study and gave a 147Sm‐143Nd isochron age of 1792 ± 35 Ma (MSWD = 3.2) consistent with the published metamorphic age of the host metasedimentary rocks. The results for both candidate reference materials and geological samples demonstrate that the in situ LA‐MC‐ICP‐MS analytical protocol described is feasible and robust for research in geological evolution.

Reverse weathering in marine sediments and the geochemical cycle of potassium in seawater: Insights from the K isotopic composition (41K/39K) of deep-sea pore-fluids

In situ Al-silicate formation, also known as “reverse weathering,” is an important sink of many of the major and minor cations in seawater (e.g. Mg, K, and Li). However, the importance of this sink in global geochemical cycles and isotopic budgets of these elements remains poorly constrained. Here, we report on the potassium isotopic composition (41K/39K) of deep-sea sediment pore-fluids from four (Integrated) Ocean Drilling Program sites (1052, U1378, U1395 and U1403) to characterize potassium isotopic fractionation associated with the formation of authigenic Al-silicate minerals in marine sediments and its role in elevating the 41K/39K of seawater relative to bulk silicate Earth. Isotopic ratios are obtained by high-resolution multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in cold plasma conditions with a long-term external reproducibility of ca. 0.17‰. We find that, although all sites are characterized by pore-fluid K concentrations that decline with increasing depth, their K isotopic profiles vary systematically from site-to-site; at sites characterized by rapid sedimentation rates, pore-fluid profiles of 41K/39K are relatively invariant whereas at sites characterized by slow sedimentation rates, 41K/39K declines with depth by up to 1.8‰. Results from 1-D diffusion-advection-reaction models suggest that these differences may result from a complex interplay between sedimentation rate and fractionation of K isotopes during diffusion, Al-silicate authigenesis, and ion exchange. Model simulations suggest fractionation factors between 0.9980 and 1.0000 for reverse weathering reactions in deep-sea sediments. Although deep-sea sites do not constitute major sinks of K in seawater, some of the processes responsible for K isotopic fractionation at these sites (diffusion and Al-silicate authigenesis) likely play a role in determining the 41K/39K of seawater.

Large Ca stable isotopic (δ44/40Ca) variation in a hand-specimen sized spheroidally weathered diabase due to selective weathering of clinopyroxene and plagioclase

Calcium stable isotopic compositions (delta Ca-44/40(SRM 915a)) as well as selected major and trace element concentrations are reported for micro-drilled samples of a hand-specimen sized spheroidally weathered diabase (synonymously used as dolerite or microgabbro) from southern India. A sample of the similar to 2.37 Ga old unweathered diabase (UW) dike was also analyzed. X-ray micro-CT imaging of a representative portion of the weathered sample shows the presence of two dominant mineral phases, plagioclase and clinopyroxene, with minor proportions of an iron-bearing phase (possibly haematite or ilmenite). Two different generations of crosscutting micro-fractures are identified from the micro-CT image. The older fracture is sealed with secondary mineral deposits. The delta Ca-44/40 values of the weathered samples range from 0.42 parts per thousand to 0.84 parts per thousand with samples showing both higher and lower values than that of the un-weathered diabase dike which shows a delta Ca-44/40 value of 0.65 parts per thousand. The variation in delta Ca-44/40 in the weathered samples is significantly higher than the external reproducibility of our measurements (< 0.1 parts per thousand) based on multiple measurements of Ca isotopic standards SRM 915a, SRM 915b and seawater (NASS-6). Mass balance calculations based on Sr/Ca and delta Ca-44/40 values rule out the contributions of secondary silicate as well as carbonate minerals in causing the variability of delta Ca-44/40 in the weathered samples. The positive correlations between delta Ca-44/40 and Mg/Al, Mg/Na in the weathered samples further negate the possible contribution of secondary carbonates in causing the variability in delta Ca-44/40, as Al and Na are unlikely to be present in carbonates. The samples with lower delta Ca-44/40 show higher CIA (Chemical Index of Alteration) values and Al/Ca than the UW diabase while samples having higher delta Ca-44/40 show lower CIA and Al/Ca than the UW diabase. The weathered sample having the lowest delta Ca-44/40 (close to the delta Ca-44/40 of plagioclase) exhibits the highest value of europium anomaly (Eu/Eu*). These observations are explained by the presence of variable relative proportions of residual clinopyroxene and plagioclase in the weathered diabase, due to selective weathering of these minerals. Since plagioclase and clinopyroxene could not be separated from the diabase, we measured the Ca isotopic compositions of a clinopyroxene (delta Ca-44/40= 1.06 parts per thousand) from the San Carlos mantle peridotite and plagioclase from the Chilka anorthosite complex (delta Ca-44/40= 0.40 parts per thousand) from the Eastern Ghats and used these isotopic values as representative of the compositions of these minerals in the diabase. Based on mixing models, using delta Ca-44/40, Al/Ca and Sr/Ca of the plagioclase and clinopyroxene end-members, we estimate that the delta Ca-44/40 of the UW diabase can be explained by 31 parts per thousand clinopyroxene and 69 parts per thousand plagioclase, which is consistent with the modal proportion of these minerals in an average unweathered diabase. Based on mixing calculations, the delta Ca-44/40, Sr/Ca and Al/Ca variability of the micro-drilled samples of the weathered diabase are explained by the presence of varying proportions of residual clinopyroxene (20-65 parts per thousand) and plagioclase (80-35 parts per thousand) in the weathered rock. This study demonstrates that selective weathering of major rock-forming minerals in nature can result in significant variation in delta Ca-44/40 in weathered rocks and that selective weathering of rock-forming minerals should be considered as an additional mechanism to explain the delta Ca-44/40 variability in rivers.

Reproducibility of preclinical animal research improves with heterogeneity of study samples.

Single-laboratory studies conducted under highly standardized conditions are the gold standard in preclinical animal research. Using simulations based on 440 preclinical studies across 13 different interventions in animal models of stroke, myocardial infarction, and breast cancer, we compared the accuracy of effect size estimates between single-laboratory and multi-laboratory study designs. Single-laboratory studies generally failed to predict effect size accurately, and larger sample sizes rendered effect size estimates even less accurate. By contrast, multi-laboratory designs including as few as 2 to 4 laboratories increased coverage probability by up to 42 percentage points without a need for larger sample sizes. These findings demonstrate that within-study standardization is a major cause of poor reproducibility. More representative study samples are required to improve the external validity and reproducibility of preclinical animal research and to prevent wasting animals and resources for inconclusive research.

High-precision strontium isotope analysis of geological samples by thermal ionisation mass spectrometry

Abstract We present a method for the efficient separation of Sr from geological materials followed by high-precision measurement of Sr isotopes by thermal ionisation mass spectrometry (TIMS). These analyses focus on high-precision measurements of the low abundance isotope 84Sr (0.56%), which is of high interest for cosmochemical applications. The robust dataset obtained through the analysis of a range of basalts and anorthosites sheds light on a number of issues regarding Sr isotopic analyses. Specifically, concerns that analytical artefacts may produce a spurious signal on 84Sr have been investigated. The external reproducibility, based on replicate measurements of the basalt standard BCR-2, for e84Sr is ±0.36 (2SD), and is ±0.51 (2SD) for repeated analyses of NIST SRM-987. In contrast with the static measurements of previous work (Andreasen and Sharma, 2007; Moynier et al., 2012; Paton et al., 2013; Brennecka et al., 2013), our dynamic data reveal no 84Sr variations in terrestrial rocks or standard material. The dataset indicates that, by the analytical procedure employed, 84Sr variations in extra-terrestrial material larger than ~0.5e are resolvable.

A novel sample loading method and protocol for monitoring sample fractionation for high precision Ca stable isotope ratio measurements using double-spike TIMS

The external reproducibility (2σSD) of Ca stable isotope ratio measurements (δ44/40Ca) using double-spike (43Ca–48Ca) thermal ionization mass spectrometry (TIMS) is better than 0.08 ‰ using our proposed loading technique.

Matrix Effects Originating from Coexisting Minerals and Accurate Determination of Stable Silver Isotopes in Silver Deposits.

Except for extensive studies in core formation and volatile-element depletion processes using radiogenic Ag isotopes (i.e., the Pd-Ag chronometer), recent research has revealed that the mass fractionation of silver isotopes is in principle controlled by physicochemical processes (e.g., evaporation, diffusion, chemical exchange, etc.) during magmatic emplacement and hydrothermal alteration. As these geologic processes only produce very minor variations of δ109Ag from -0.5 to +1.1‰, more accurate and precise measurements are required. In this work, a robust linear relationship between instrumental mass discrimination of Ag and Pd isotopes was obtained at the Ag/Pd molar ratio of 1:20. In Au-Ag ore deposits, silver minerals have complex paragenetic relationships with other minerals (e.g., chalcopyrite, sphalerite, galena, pyrite, etc.). It is difficult to remove such abundant impurities completely because the other metals are tens to thousands of times richer than silver. Both quantitative evaluation of matrix effects and modification of chemical chromatography were carried out to deal with the problems. Isobaric inferences (e.g., 65Cu40Ar+ to 105Pd, 208Pb2+ to 104Pd, and 67Zn40Ar+ to 107Ag+) and space charge effects dramatically shift the measured δ109Ag values. The selection of alternative Pd isotope pairs is effective in eliminating spectral matrix effects so as to ensure accurate analysis under the largest possible ranges for metal impurities, which are Cu/Ag ≤ 50:1, Fe/Ag ≤ 600:1, Pb/Ag ≤ 10:1, and Zn/Ag ≤ 1:1, respectively. With the modified procedure, we reported silver isotope compositions (δ109Ag) in geological standard materials and typical Au-Ag ore deposit samples varying from -0.029 to +0.689 ‰ with external reproducibility of ±0.009-0.084 ‰. A systemic survey of δ109Ag (or ε109Ag) variations in rocks, ore deposits, and environmental materials in nature is discussed.

A Reassessment of the Precision of Carbonate Clumped Isotope Measurements: Implications for Calibrations and Paleoclimate Reconstructions

AbstractCarbonate clumped isotopes offer a potentially transformational tool to interpret Earth's history, but the proxy is still limited by poor interlaboratory reproducibility. Here, we focus on the uncertainties that result from the analysis of only a few replicate measurements to understand the extent to which unconstrained errors affect calibration relationships and paleoclimate reconstructions. We find that highly precise data can be routinely obtained with multiple replicate analyses, but this is not always done in many laboratories. For instance, using published estimates of external reproducibilities we find that typical clumped isotope measurements (three replicate analyses) have margins of error at the 95% confidence level (CL) that are too large for many applications. These errors, however, can be systematically reduced with more replicate measurements. Second, using a Monte Carlo‐type simulation we demonstrate that the degree of disagreement on published calibration slopes is about what we should expect considering the precision of Δ47 data, the number of samples and replicate analyses, and the temperature range covered in published calibrations. Finally, we show that the way errors are typically reported in clumped isotope data can be problematic and lead to the impression that data are more precise than warranted. We recommend that uncertainties in Δ47 data should no longer be reported as the standard error of a few replicate measurements. Instead, uncertainties should be reported as margins of error at a specified confidence level (e.g., 68% or 95% CL). These error bars are a more realistic indication of the reliability of a measurement.

Development of a Diagnostic Programmed Cell Death 1-Ligand 1 Immunohistochemistry Assay for Nivolumab Therapy in Melanoma.

Nivolumab is a monoclonal antibody that blocks the interaction between programmed cell death 1 (PD1) and programmed cell death 1-ligand 1 (PD-L1), resulting in enhanced antitumor activity by the immune system. Nivolumab is currently approved by the US Food and Drug Administration (FDA) for melanoma, non-small cell lung cancer (NSCLC), renal cell carcinoma, classical Hodgkin lymphoma, squamous cell carcinoma of the head and neck, and urothelial carcinoma. PD-L1 IHC 28-8 pharmDx is FDA-approved as a complementary diagnostic for immunohistochemical (IHC) detection of PD-L1 in non-squamous NSCLC and melanoma. We report validation of PD-L1 IHC 28-8 pharmDx for PD-L1 detection on formalin-fixed, paraffin-embedded human melanoma specimens using Autostainer Link 48. A prevalence assessment of 104 melanoma specimens indicated that PD-L1 was detected across the full expression level range (0% to 100% of tumor cells). Assay robustness and precision studies were conducted at Agilent Technologies, with additional reproducibility studies performed at 3 external laboratories. Precision studies evaluated at ≥1% and ≥5% expression levels revealed a range of average negative agreement from 89.5%, 95% CI (83.2, 93.6) to 100%, 95% CI (97.3, 100), and average positive agreement from 85.5%, 95% CI (77.6, 90.9) to 100%, 95% CI (97.9, 100). For external reproducibility, precise results were obtained. These results demonstrate PD-L1 IHC 28-8 pharmDx is a precise, robust, and reproducible assay for determining PD-L1 expression in melanoma. This is the first PD-L1 IHC test to receive FDA approval as a complementary diagnostic in melanoma patients whereby positive PD-L1 expression is correlated with the magnitude of nivolumab treatment effect.

Analysis of molecular isotopic structures at high precision and accuracy by Orbitrap mass spectrometry

Several technologies are being developed to examine the intramolecular isotopic structures of molecules (i.e., site-specific and multiple substitution), but limitations in sample size and type or (for mass spectrometry) resolution have so far prevented the creation of a general technique. We have now demonstrated the capacity for precise and accurate study of molecular isotopic contents and structures by Fourier transform mass spectrometry, using instruments containing a Thermo Scientific™ Orbitrap™ mass analyzer, here the Thermo Scientific Q Exactive GC™ and Q Exactive HF™ instruments. Orbitrap mass analyzers achieve mass resolutions in the range ∼250,000–1M (FWHM) in the mass range of greatest interest to studies of molecular isotopic structure, 50–200amu. This allows for resolution of many nearly isobaric interferences for compounds containing H, C, N, O and/or S. In this paper we show that internal and external experimental reproducibilities of isotope ratio analyses using the Orbitrap analysis can conform to shot-noise limits down to levels of tenths of per mil (1SE), with similar accuracy when standardized to reference materials. Precision reaches ±0.015‰ for exceptionally long integrations. Such measurements do not call for modifications to the ion optics of the Q Exactive instruments, but do require specially designed sample introduction devices to permit sample/standard comparison and long integration times. The sensitivity of the Q Exactive instruments permit analysis of sub-nanomolar samples and quantification of multiply-substituted species. Site-specific capabilities arise from the fact that mass spectra of molecular analytes commonly contain diverse fragment ion species, each of which samples a specific sub-set of molecular sites.

Cross-cultural adaptation and content and semantic validation of the Difficult Intravenous Access Score for pediatric use in Brazil

ABSTRACTObjective:present the cross-cultural adaptation and content and semantic validation of the Difficult Intravenous Access Score for current use in Brazil. Method:cross-cultural adaptation and validation study, structured in six phases: initial translation, synthesis of translations, back-translation, assessment of documents by expert committee of specialized judges, pretest and presentation of the documents to the expert judges and to the author of the original instrument. Twenty health professionals were randomly recruited from a public hospital in the South of Brazil, working in pediatrics, in order to assess the agreement level with the variables in the instrument. In addition, a convenience sample of 30 pediatric patients was selected for the face validation of the same instrument. Cronbach’s alpha coefficient, simple and percentage frequencies, the Shapiro-Wilk and Fisher’s exact tests were used for the data analysis and reliability measures. Results:the cross-cultural adaptation phases were executed with totally clear translated variables, demonstrating satisfactory results in the content and semantic validation process. Conclusions:the Difficult Intravenous Access Score was adapted and its content and semantics were validated. External clinical validity, measuring equivalence and reproducibility analyses are needed.