Lower Limit Research Articles

Highly Efficient Manganese Bromides with Reversible Luminescence Switching through Amorphous-Crystalline Transition.

While luminescent stimuli-responsive materials (LSRMs) have become one of the most sought-after materials owing to their potential in optoelectronic applications, the use of earth-scarce lanthanides remains a crucial problem to be solved for further development. In this work, two manganese-based LSRMs, (R)-(+)-1-phenylethylammonium manganese bromide, (R-PEA)2MnBr4, and (S)-(-)-1-phenylethylammonium manganese bromide, (S-PEA)2MnBr4, are successfully demonstrated. Both (R-PEA)2MnBr4 and (S-PEA)2MnBr4 show a kinetically stable red-emissive amorphous state and a thermodynamically stable green-emissive crystalline state at room temperature, where the fully reversible transition can be done through melt-quenching and annealing processes. Based on this property, a reusable manganese-halide-based time-temperature indicator is demonstrated for the first time. Furthermore, an X-ray scintillator with a low limit of detection (18.1 nGy/s) and a high spatial resolution limit (30.0 lp/mm) are achieved by exploiting the high transparency of amorphous states. These results uncover the multifunctionality of manganese halides and pave the way for upcoming research.

Distinguishing Surface and Bulk Reactivity: Concentration-Dependent Kinetics of Iodide Oxidation by Ozone in Microdroplets.

Iodine oxidation reactions play an important role in environmental, biological, and industrial contexts. The multiphase reaction between aqueous iodide and ozone is of particular interest due to its prevalence in the marine atmosphere and unique reactivity at the air-water interface. Here, we explore the concentration dependence of the I- + O3 reaction in levitated microdroplets under both acidic and basic conditions. To interpret the experimental kinetics, molecular simulations are used to benchmark a kinetic model, which enables insight into the reactivity of the interface, the nanometer-scale subsurface region, and the bulk interior of the droplet. For all experiments, a kinetic description of gas- and liquid-phase diffusion is critical to interpreting the results. We find that the surface dominates the iodide oxidation kinetics under concentrated and acidic conditions, with the reactive uptake coefficient approaching an upper limit of 10-2 at pH 3. In contrast, reactions in the subsurface dominate under more dilute and alkaline conditions, with inhibition of the surface reaction at pH 12 and an uptake coefficient that is 10× smaller. The origin of a changing surface mechanism with pH is explored and compared to previous ozone-dependent measurements.

Tissue transglutaminase immunoglobulin A exceeds endomysial antibody in specificity of celiac diagnosis at ≥10 times the upper limit of normal.

Serologic diagnosis using tissue transglutaminase immunoglobulin A (TTG-IgA) and endomysial antibody (EMA) is being integrated into the care of pediatric patients with positive screening for celiac disease. The purpose of this study was to assess the utility of EMA in pediatric patients being considered for serologic diagnosis. Patients with TTG-IgA testing performed between May 1, 2022 and April 30, 2023 and with subsequent duodenal biopsy within 6 months were included. TTG-IgA serum samples were frozen and sent for EMA testing and titer. EMA was evaluated for positivity and TTG-IgA (normal <15 u/mL) for elevation <10 times (10x) the upper limit of normal (ULN) and ≥10x ULN (≥150 u/mL). Sensitivity and specificity of EMA and TTG-IgA were calculated using biopsy histology as the gold standard. Four hundred and eighty-six patients were included. The sensitivity and specificity of TTG-IgA ≥15 u/mL was 87.5% and 95.4% while EMA was 77.5% and 97.3%. For patients with TTG-IgA ≥10x ULN the specificity was 99.3%. The positive predictive value of TTG-IgA at ≥10x ULN was 91.4% and for EMA was 83.6%. All three patients with false positive TTG-IgA ≥10x ULN also had false positive EMA, and two of these patients had type 1 diabetes mellitus. TTG-IgA has greater sensitivity at the screening threshold of ≥15 u/mL and greater specificity and positive predictive value at ≥10x ULN than EMA. TTG-IgA at ≥10x ULN is superior to EMA for the serologic diagnosis of celiac disease.

A-093 Assessing Alkaline Phosphatase Reference Intervals Using Gamma-Glutamyl Transferase as a Surrogate for Normal Liver Function

Abstract Background There are limited published studies assessing reference intervals (RIs) for hepatic enzymes, particularly for alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT). In the US, ALP and GGT RIs were established on Roche assays using a European cohort of ≤ 450 patients that may not reflect population variance across practice settings. Further, age- and sex-specific variation in ALP and GGT may warrant tiered RIs, but evidence to justify this approach is limited. We aimed to evaluate the manufacturer’s RIs by comparing them to indirectly estimated RIs (IRIs) from routine clinical data. Methods 217,333 AST, ALT, ALP, and GGT results (Roche c702) performed between 1/1/2019-12/31/2022 on outpatients ≥21 years were extracted from the laboratory information system. The first ALP for each patient was identified, and the earliest AST, ALT, and GGT drawn within 7 days was included. This approach was repeated for GGT. Concordance and correlation were calculated using Weighted Cohen’s Kappa and Spearman’s rank correlation coefficient respectively. {refineR}, an algorithm for calculating IRIs, was applied to patients with “normal” liver function (defined as normal AST, ALT for all IRIs, plus normal GGT for ALP IRIs, and ALP for GGT IRIs). IRIs were estimated for all males, all females, females ≤50, and females &amp;gt;50 years and compared to the method specific manufacturer RI (ALP: 40-129 Units/L for males and 35-104 Units/L for females; GGT: 8-61 Units/L for males and 5-36 Units/L for females). Results Of the 71,783 outpatients, 54.9% were female, 74% self-identified as white and 19% as black. The median age was 58 (IQR: 43-68 years), the median ALP concentration was 77 (62-97 Units/L), and the median GGT concentration was 28 (17-57 Units/L). A moderate agreement between ALP and GGT was observed (Kappa = 0.48, 95% confidence interval: 0.46-0.51). A positive correlation between ALP and GGT was observed r = 0.51 (p&amp;lt;0.0001). For ALP, no significant differences were observed between the lower limit of the IRIs and the current RI. The upper limit of estimated IRIs was 132 [95% confidence interval: 117-147 Units/L] for patients with normal AST/ALT/GGT (n = 1596). For males, the sex-specific upper limit was 120 [101-140 Units/L] and for females, was 123 [110-136 Units/L]. Age stratified upper limits for females were 120 [101-140 Units/L], and 109 [97-121 Units/L] for ≤50 and &amp;gt;50 years, respectively. For GGT, no significant differences were observed for the lower limits. The upper limit for all patients with normal AST/ALT/ALP (n = 2,446) was 62 [55-70 Units/L]. For males, all females, females ≤50 and &amp;gt;50 years was 58 [46-69 Units/L], 40 [39-51 Units/L], 31 [23-39 Units/L], and 56 [41-71 Units/L]. Conclusions For the majority of patient subsets, the manufacturer RI agreed well with the IRIs. However, significant differences in IRIs were observed for the upper limit of ALP IRIs of all females with normal hepatobilliary function and in GGT for all females and females &amp;gt;50 years. Further investigation of the impact of preselecting patient populations on IRI estimation and a direct RI study on select patient subsets is worth investigation.

B-310 Freezing and thawing serum without mixing prior to analysis causes false low Thyroglobulin results

Abstract Background Thyroglobulin (Tg), a glycoprotein that is synthesized in follicular cells of the thyroid gland, is the precursor of Thyroxin (T4) and Triiodothyronine (T3). Tg is a biomarker used for many clinical conditions, including monitoring for recurrence in patients with differentiated thyroid carcinoma. Typically, Tg levels drop to very low or undetectable levels after surgical excision and/or radioiodine ablation of the thyroid, with post-operative levels greater than 1-2 ng/ml indicating potential disease recurrence. Discordant Tg results in a patient sample were identified during a quality check of Tg results. This study investigates the root of cause of the discrepant Tg results. Given that: 1) Tg analyses were performed twice a week at our laboratory due to low daily test volume and patients’ samples received on an unanalytical day were stored at -20°C until analysis; 2) Tg analyses were performed by various medical technologists; 3) sample mixation prior to analysis was not routine practice for our automated laboratory, we hypothesized that the discrepancy was due to inconsistent sample handling, e.g., mixation vs unmixation prior to analysis. Methods Analysis of the daily QC and PT results in the period of the incident occurence ruled out causes in analytical phase. We split 52 de-identified patient serum samples into two equal aliquots and subsequently stored both aliquots at -20°C for 48 hours. Both aliquots of each sample were thawed at room temperature for 1 hour. One of the aliquots was analyzed for Tg without mixing, and the other was analyzed after mixing using a Vortexer for 4 seconds at 250 xg. To investigate if Tg concentrations form a gradient from the top to the bottom of a red-top vacutainer tube, five patient samples with Tg at 2.59, 2.79, 2.92, 52.37 and 144.12 ng/mL were thawed without mixing following storage at -20°C for 48 hours. Five layer (600 μl/layer) aliquots were carefully and sequentially taken from top to bottom for each specimen, and the Tg concentration in the aliquot of each layer was determined using the Beckman Coulter Access-2 Immunoassay. Results Of the 52 patients samples, 14 Tg results were excluded from statistical analysis due to exceeding the assay dynamic range (2 above and 12 below the upper and low limits, respectively). Analysis of the remaining 38 patient samples showed the mean of Tg concentrations was 22.8% (SD 18%) higher in mixed samples than the un-mixed samples. Regression analysis showed an R2 = 0.9976 (Mixed Tg = 1.1523 x Un-mixed + 0.4174, range 0.1 - 275.7 ng/mL, intercept 95%CI -0.721 to 1.556, slop 95%CI 1.1331 to 1.1715, p-value &amp;lt;0.001). Results of Tg gradient analysis showed significant higher Tg values in the 2nd, 3rd, 4th and 5th than the 1st layer by 26% (SD 11%), 63% (26%), 112% (57%), and 160% (76%), respectively. Conclusions False Tg values were found in samples without mixing before analysis after thawing from frozen state, due to formation of Tg concentration gradient in test tube. For obtaining reliable results, samples must be mixed before analysis when thawed from frozen storage.

A-315 Cardiac Troponin Concentrations in Pediatric Patients Infected with Respiratory Syncytial Virus

Abstract Background Respiratory syncytial virus (RSV) is associated with considerable morbidity and mortality in pediatric patients. Cardiac troponin I (TnI) has been shown to increase in patients with acute respiratory illness, including COVID-19. The impact of RSV infection on circulating TnI has been formally demonstrated in the literature. The goal of this study was to assess the relationship between TnI and respiratory syncytial virus (RSV) in pediatric patients. Methods A prospective study was conducted at St. Louis Children’s Hospital from October 2023 to February 2024. Patients older than 6 months who presented to the ED and had a CBC ordered within 6 hours of testing positive for RSV on the Biofire® FilmArray® Respiratory Panel were enrolled. Patients with Rhinovirus, Enterovirus, Streptococcus pneumoniae, or Adenovirus infections were included as controls. Remnant EDTA specimens were tested on an Abbott ARCHITECT i2000 for high sensitivity TnI (hs-TnI) with a limit of detection of 1.4 ng/L and a limit of quantitation of 3.5 ng/L. 99% upper reference limits from the CALIPER database on the Abbott of &amp;lt;7 ng/L were used as a threshold for positive results. The electronic medical record (EPIC) was assessed for demographic information and outcomes including length of stay (LOS), intensive care unit (ICU) length of stay, requirement of supplemental oxygen, white blood cell count (WBC), and creatinine. Results A total of 103 patients had RSV and 35 had other respiratory infections (ORI). The average age for the RSV positive group was 2.3 and for the ORI group was 2.4. Males made up 61% of the RSV+ group and 51% of the ORIs. 93 patients in the RSV group were admitted. The median TnI for RSV patients was 1.4 (IQR, 1.2-2.9) and for ORIs was 1.4 (IQR, 1.4-6.8). TnI was measurable in 58% of those with RSV and 54% in ORIs. We next assessed the correlation between hospital LOS and TnI in RSV+ patients, with a Pearson r of 0.42 (95% CI= 0.23-0.58). There was no correlation between WBC and LOS (r=-0.04, 95% CI=-0.25-0.17). There was also no correlation between TnI and WBCs or creatinine. Of admitted patients, 44 (47%) in the RSV group were in the ICU compared to 18 (51.4%) in those with ORIs. RSV+ patients that required ICU treatment had comparable TnI (1.4, IQR, 0.9-3.5) to those that didn’t require ICU stay (1.4, IQR, 0.75-1.5). There was no correlation between ICU LOS and TnI in RSV+ patients (r=-0.08, 95% CI=-0.39-0.24). There was a significant difference in mean TnI concentrations in RSV+ patients that required supplemental oxygen (8.7, 95% CI: 0-19) versus those that did not (1.7, 95% CI: 1.1-2.4). Conclusions There was no difference in TnI in patients hospitalized for RSV relative to ORIs. While TnI concentration was associated with LOS, there were minimally other associations between TnI and outcomes in patients hospitalized with RSV. While TnI elevations are associated with acute respiratory infections in adults, the impact on pediatric patients is not as clear. Future investigation is needed to understand how severe respiratory infections impact pediatric cardiac function.

B-313 Assessment of β2-microglobulin concentration in pleural effusions

Abstract Background β2-microglobulin (β2-m) is a biomarker used in serum for different types of pathologies. It has been described that lymphocyte activation processes us tuberculosis infections, AIDS virus or cytomegalovirus infections, can produce an increase in the concentration of this marker. As a tumor marker is useful in lymphomas diagnosis. In the bibliography has reported that processes involving renal failure lead to a significant increase in its concentration. In patients with renal failure and treated with hemodialysis, have been described medians twenty times the upper reference limit. The objective is to assess whether the concentration of (β2-m) in pleural fluid is affected by the same factors as in serum. Methods We analyzed 303 pleural effusions (PE) samples from undiagnosed patients with pleural effusion. β2-microglobulin levels were prospectively measured by electrochemiluminescence (ECLIA) assays (Cobas c702, Roche Diagnostics®). Glomerular filtration rate (GFR) was calculated by CKD-EPI equation. The diagnostic performance of β2-microglobulin was evaluated by receiver operating characteristic (ROC) curve analysis. Statistical analyses were performed using SPSS software. Results Pleural fluid of 303 patients (104 female, 204 male) were collected. The median age was 72 ± 10,6 years. For all samples β2-m median concentration was 5,85 mg/L (IQR:3.4 -6.45).When we compared all results according to kidney failure values; GFR &amp;gt;60mL/min β2-m median concentration was 4,12mg/L and if GFR &amp;lt;60 mL/min, β2-m was 8,62g/L significant difference have found (p&amp;lt;0,001). Comparing results between malignant pleural effusions (MPE) (n=96) and benign pleural effusions (BPE) (n=207), MPE median concentration was 5.38 mg/L and 6.07mg/L significant difference (p&amp;lt;0,001). Benign pathologies associated with pleural effusions, tuberculosis samples had the highest concentration of β2-m. Tuberculosis samples (n=6) had a normal distribution, obtaining a value [mean (SD)] of 7.28 mg/mL (2,13) mg/mL. For tuberculosis samples and patients without renal failure (n=5) (GFR&amp;gt;60 mL/min), the area under the ROC curve was 0.98 (95% CI: 0.88-0.98) (p&amp;lt;0.005). For β2-m cut-off point was 5.150 mg/L, a sensitivity of 100%, specificity of 16%, positive predictive value (PPV) of 14% and negative predictive value (NPV) of 100% were obtained. Patients with lymphomas present the highest concentration in the group of malignant pleural effusions, but further investigations could not be performed due to the small sample size. Conclusions Based on the results obtained from our present study, it can be concluded that β2-microglobulin marker in pleural effusions has significant association with glomerular filtration rate, as well as occurs in serum. Higher concentrations were found in patients with GFR&amp;gt;60 mL/min and tuberculosis. Using 5,15 mg/L cut-off point, 100% of NPV was obtained.

B-159 Fast Cleanup for 19 Steroid Analytes in Serum Using Supported Liquid Extraction (SLE)

Abstract Background Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a powerful tool that holds promise in designing the future of steroid analysis in the clinical laboratory. It is already widely used in steroid analysis in endocrinology and is being utilized increasingly in newer applications for individual steroids and panels relevant in clinical research. LC-MS/MS is gaining user base owing to greater sensitivity and specificity and gradually even replacing some of the legacy test methods. Improved sample preparation, modern chromatography methods, and sensitive, faster scanning mass spectrometers have all played a role in improving LC-MS/MS. Steroid analysis for clinical research can require very low limits of detection which demand high recoveries and very clean extracted samples. Supported Liquid Extraction (SLE) can provide very clean extracted samples with less method development and a streamlined workflow compared to solid phase extraction (SPE). Laboratories desire high-throughput methods which consolidate analytes into one panel with fast chromatographic run times. Chromatographic separation of steroid isomers with the same m/z is necessary for accurate quantitation by LCMS/MS. Meeting these criteria can be challenging in a single LC-MS/MS method. Methods Each 200 µL serum sample was pretreated with 200 µL of pH 6 Ammonium Acetate buffer (aq) before being loaded onto a Novum™ PRO SLE, MAX 96-well plate, following the standard SLE protocol. Samples were eluted using 2 × 900 µL of Dichloromethane or Ethyl Acetate. After evaporation of the elution solvent, samples were reconstituted in 100 µL of 0.5 mM Ammonium Fluoride / Methanol (60:40, v/v). A Kinetex™ 2.6 μm C18, 50 x 3.0 mm column using a gradient of 0.5 mM Ammonium Fluoride (aq) and Methanol on an Agilent® 1290 Infinity UHPLC and SCIEX® 7500 Triple Quad™ were used for quantitation. Results Here, we present an effective sample extraction method and LC-MS/MS analysis method for the quantitation of a 19-analyte steroid panel from serum. The Kinetex 2.6 μm C18 column provided a fast 8-minute chromatographic separation and good selectivity for steroid analytes in both positive ion mode and negative ion mode. Calibration curves with a linear fit and 1/x weighting, showed good linearity with R2 of &amp;gt;0.99 for all analytes except 17-OH-Pregnenolone and DHEAS when using Dichloromethane as the elution solvent, and R2 of &amp;gt;0.980 for all analytes when using Ethyl Acetate as the elution the solvent. Accuracy of samples using Dichloromethane as the elution solvent were 80-112 %, except for 17-OH-Pregnenolone and DHEAS. Accuracy of all samples using the Ethyl Acetate elution solvent were 91-118 %. Conclusions The-96 well plate extraction method was robust, reproducible, and can be automated. SLE using Novum Pro MAX combined with a fast LC method provides a simple, rapid, high-throughput workflow for identification and quantitation of 19 steroids from serum.

Room-Temperature Flexible CNT/Fe2O3 Film Sensor for ppb-Level H2S Detection.

Carbon nanotubes (CNTs) had room temperature response, large surface area, and excellent mechanical properties, making them favorable for the design of flexible, wearable, and portable gas sensors. However, CNTs were lacking in response and selective response to different gases, such as H2S. Here, we demonstrated a flexible H2S ppb-level gas sensor based on a carbon nanotube/amorphous Fe2O3 (CNT/Fe2O3) film at room temperature, which was fabricated via a simple one-step solvent-thermal method. The CNT/Fe2O3 film gas sensor exhibited a high selective response to H2S (with a response of 55.1% to 100 ppb H2S), rapid reversible response at room temperature (with a response time of ∼127 s to 100 ppb H2S), and low limit of detection to about 2 ppb. Additionally, the CNT/Fe2O3 film maintained good sensing performance under various bending conditions and could be further fabricated into the fiber gas sensor device via wet stretching, retaining response at the ppb level (with a response of 18.6% to 100 ppb H2S). This research on a flexible gas sensor device based on the CNT film/fiber opened up new possibilities for wearable portable electronic device applications.

Magnesium geochemistry of authigenic carbonate at marine cold seep

Cold seeps, featured by their extremely methane-rich sedimentary environments, play a significant role in the geological history and are common in marine sediments across the seafloor. Primary dolomite, possibly mediated by microorganisms, can be widely discovered in methane-rich environments. Hence, cold seeps may provide new insights into the ‘dolomite problem’, which has confused geologists for decades. Magnesium isotope geochemistry of seep carbonates contributes to the understanding of the dolomite formation mechanism in marine environments. In this paper, magnesium geochemical characteristics of carbonates in modern sediments are summarized, along with rare researches on magnesium isotopes of seep carbonates. Methane vigorously interacts with sulfate by anaerobic oxidation of methane at cold seeps, producing vast amounts of dissolved sulfide which can significantly promote dolomitization of seep carbonates. Compared with temperature, alkalinity, mineralogy, etc., the competition between rapid carbonate precipitation rates and aqueous ligands may be the main factor of the magnesium fractionation at cold seeps, which is controlled by the kinetic effect. The range of magnesium isotopes of seep carbonates is narrow (from -3.46‰ to -2.36‰), and an upper limit of magnesium content seems to exist. This characteristic may be a good indicator for identifying dolomitization related to anaerobic oxidation of methane. Whereas, mechanisms of magnesium isotope fractionation and dolomitization at cold seeps remain unclear, necessitating more natural samples tested, stimulated calculation and laboratory experiment.

Determination of the Relative Sign of the Higgs Boson Couplings to W and Z Bosons Using WH Production via Vector-Boson Fusion with the ATLAS Detector

The associated production of Higgs and W bosons via vector-boson fusion is highly sensitive to the relative sign of the Higgs boson couplings to W and Z bosons. In this Letter, two searches for this process are presented, using 140 fb−1 of proton-proton collision data at s=13 TeV recorded by the ATLAS detector at the LHC. The first search targets scenarios with opposite-sign couplings of the W and Z bosons to the Higgs boson, while the second targets standard model-like scenarios with same-sign couplings. Both analyses consider Higgs boson decays into a pair of b quarks and W boson decays with an electron or muon. The data exclude the opposite-sign coupling hypothesis with a significance beyond 5σ, and the observed (expected) upper limit set on the cross section for vector-boson fusion WH production is 9.0 (8.7) times the standard model value at 95% confidence level. © 2024 CERN, for the ATLAS Collaboration 2024 CERN

Forecasting Population in an Uncertain World: Approaches, New Uses, and Troubling Limitations

AbstractThe long human lifespan enables long run forecasts of population size and age distribution. New methods include biodemographic research on upper limits to life expectancy and incorporation of early experiences affecting later life mortality such as smoking, obesity, and childhood health shocks. Some fertility forecasts incorporate education and quantum‐tempo insights. Statistical time series and Bayesian methods generate probabilistic forecasts. Yet recent decades have brought surprising changes in the economy, natural environment, and vital rates. In these changing circumstances we need new methods and the increasing use of probabilistic models and Bayesian methods incorporating outside information. The increasing use of microsimulation combined with aggregate forecasting methods is a very promising development enabling more detailed and heterogeneous forecasts. Some new uses of stochastic forecasts are interesting in themselves. Probabilistic mortality forecasts are used in finance and insurance, and a new Longevity Swap industry has been built on them. Random sample paths used to generate stochastic population forecasts can stress‐test public pension designs for fiscal stability and intergenerational equity. Population forecasting a few decades ago was a dull backwater of demographic research, but now it is increasingly important and is full of intellectual and technical challenges.

B-316 Evaluation of an FDA-cleared Chromogranin A Assay on an Automated Analyzer

Abstract Background Chromogranin A (CgA) is a hydrophilic and acidic protein, present in the chromaffin granules of neuroendocrine cells. It is the preferred tumor marker for the monitoring of neuroendocrine tumors (NETS), which are often found in the lungs, appendix, pancreas, and gastrointestinal tract. Previous CgA assays were performed by manual ELISA testing, and were not FDA-approved, leading to a longer, more rigorous validation process and longer run times. The introduction of an automated, FDA-cleared CgA assay allows the laboratory to process patient samples more quickly and reliably, shortening a multiple hour process to minutes. The objective of this study was to evaluate the performance of an automated CgA assay recently cleared by the FDA. Methods We validated the the B·R·A·H·M·S™ Chromogranin A II (CGAII) assay on the automated B·R·A·H·M·S KRYPTOR Compact PLUS (Thermo Fisher Scientific Inc.). The CGAII assay is an immunofluorescent assay, which uses Time-Resolved Amplified Cryptate Emission (TRACE) to quantitate CGA in human serum. Assay performance characteristics were evaluated including measuring range (MR) and maximum dilution, precision, method comparison, stability, reference interval, stability, and carryover. Results The MR for CGAII was established with triplicate analysis of serum at 8 levels, ranging from 25.8 - 2,700 ng/mL. Linearity was demonstrated with a slope of 0.907, intercept of 1.948 and observed error of 2.54 ng/mL. Recovery at each point ranged from 83.3-110.3%. Carryover (&amp;lt;5.0 ng/mL) was not observed at a concentration approximately 2 times the upper limit of the MR. A 1:25 or 1:500 automatic dilution was determined to be acceptable (% bias &amp;lt;16%). Intraday precision coefficient of variation (CV) ranged from 4.1-1.7% (SDs from 2.32-6.64 ng/mL) at concentrations of 56.7 and 393.0 ng/mL. The interday CVs ranged from 6.0-7.1% (SDs from 3.43 - 28.84 ng/mL) at concentrations of 57.5 and 403.8 ng/mL. Twenty samples with concentrations ranging from 56.4-2,907 ng/mL were compared to a reference laboratory utilizing a similar methodology. The correlation coefficient was 0.9934, with a slope of 1.014, and intercept of -32.95. An additional twenty samples with concentrations ranging from 67.0-2,446 ng/mL were compared to a CgA ELISA kit (CGA-ELISA-NG, CISBIO) to determine the bias between the two methodologies. The correlation coefficient was 0.9902, with a slope of 0.845, and intercept of -15.31, and a bias of -19.9%. The serum samples were stable for 3 days when stored at 2-8°C. Recovered CgA concentrations fell outside of the 95% confidence interval after day 3 at 2-8°C. The manufacturer provided reference interval of &amp;lt;187 ng/mL was verified by testing 20 healthy adult samples, all of which fell within this range. Conclusions This assay has been validated and shown to be an accurate and precise method for monitoring CgA. Further, the method was validated on an automated analyzer to allow expeditious turnaround time in a core laboratory.

A-009 Analytical Characterization of a Novel NT-proBNP Assay on a Central Laboratory Platform

Abstract Background N-terminal pro-B-type Natriuretic Peptide (NT-proBNP) or B-type Natriuretic Peptide (BNP) assay(s) are widely measured with a Class 1, Level of Evidence A recommendation in professional heart failure (HF) guidelines for diagnosis and prognosis. We present the analytical characteristics of the first NT-proBNP assay on Beckman Coulter platforms. Methods Measurements were conducted with the Access NT-proBNP assay, a one-step sandwich immunoenzymatic assay using monoclonal capture and detection antibodies, on the DxI 9000 Immunoassay Analyzer with Lithium Heparin (LiHep) plasma samples. Performance was characterized according to CLSI guidelines for: Limit of Blank (LoB), Limit of Detection (LoD), Limit of Quantitation (LoQ), linearity, imprecision (repeatability, reproducibility) and matrix comparison with LiHep, EDTA and serum. Reference intervals (RI) were evaluated in a healthy, adult U.S. population comprised of 675 subjects with 54.6% females, 79.1% White and 15.1% Black individuals. Exclusion criteria included elevated cardiac troponin, abnormal eGFR and cardiac medications. The 97.5th percentile RI upper limit was defined for age-stratified ranges of &amp;lt;50, 50-75, and &amp;gt;75 years old. Results Performance was LoB=1.1ng/L; LoD=4.8ng/L; LoQ=4.8ng/L; linearity=35,000ng/L. Repeatability ranged from 1.5%-3.5% and reproducibility from 2.3%-7.9% in seven samples ranging from 38ng/L to 23,848ng/L. Matrix measurement regression (n=68) yielded slopes of 1.00, 1.01; intercepts -0.03 to -2.63; r=0.98. Table 1 shows that NT-proBNP values increase with age and women generally have higher values than men. Conclusions The LoB, LoD and LoQ demonstrate highly sensitive low-end characteristics. Repeatability and reproducibility show excellent performance across a wide measurement range. NT-proBNP values are known to be age dependent, and the age-stratified 97.5th percentile RI upper limits were 162 ng/L for &amp;lt;50 years, 311 ng/L for 50-70 years, and 457 ng/L for &amp;gt;75 years. This novel Access NT-proBNP assay offers robust analytical performance as an aid to clinical HF management in acute settings.

B-035 Atellica CI Analyzer Sample-to-sample Carryover Performance Evaluation

Abstract Background Laboratories in many parts of the world are required to demonstrate/confirm the lack of sample carryover on their analyzer under their laboratory conditions using patient populations. Sample carryover occurs when analyte adheres to the probe and/or cuvette and contaminates a subsequent sample or cuvette in the testing sequence of the analyzer. Inadequate washing of the sample aspiration/ dispensing device and cuvette can cause this type of carryover. The Atellica® CI Analyzer uses independent integration and random-access sampling to process chemistry (CH) and immunoassay (IM) tests. The immunoassays performed on the IM portion of the analyzer utilizes a single-use, disposable sample tip and reaction cuvette which reduces sample carryover from IM to CH tests, whereas a reusable probe is used for CH assays—which is washed between sampling. This study evaluated the potential for carryover of CH samples from one sample to the next due to washing protocols on the Atellica® CI Analyzer in four independent real world clinical laboratories. Methods Carryover verification was performed as per CLSI GP31-A:2009 and Vericheck protocols. The study was conducted at four sites (UAE, France, Croatia, U.S.) using 2 serum samples prepared in 12 sample containers-9 for low (L) and 3 for high (H) concentrations of analyte. For glucose (GluH_3), UAE, L and H were 63 and 356 mg/dL (3.5 and 19.8 mmol/L), Croatia, 77.4 and 237.5 mg/dL (4.3 and 12.2 mmol/L), and U.S., 101 and 374 mg/dL (5.6 and 20.8 mmol/L). For creatine kinase (CK_L), France, L and H were 40 and 1400 U/L. Samples were tested in a defined sequence: L1, L2, L3, H1, L4, H2, L5, H3, L6, L7, L8, L9 and results analyzed for % carryover. Carryover was defined as average of L4, L5, L6 minus the average of L1, L2, L3, L7, L8, L9 divided by the average of H1, H2, H3. Results No significant carryover was observed at any site. Carryover % for UAE, France, Croatia, and U.S was 0.500%, -0.085%, -0.095%, and -0.095%, respectively. Conclusions When using high positive samples at concentrations at or greater than the upper limit of the clinical range, negligible CH sample carryover was found from the Atellica CI Analyzers in four independent real world clinical laboratory settings.

A-133 Trusted Test Goes Awry: Investigating Dilution Aberrations for Total Bilirubin

Abstract Background A patient with acute decompensated cirrhosis was hospitalized due to lightheadedness and jaundice, undergoing evaluation for a liver transplant. The attending physician brought to the laboratory’s attention a perplexing pattern in the patient's total bilirubin results. Initially, the patient displayed a consistent trend of elevated total bilirubin levels above the upper limit of linearity, ULOL (&amp;gt; 30 mg/dL), which then plummeted to under the limit of quantification (&amp;lt; 0.1 mg/dL) before surging back to &amp;gt; 30 mg/dL. Methods The total bilirubin in heparinized plasma was measured on the AU5800 by Beckman Coulter. Samples &amp;gt; ULOL are diluted automatically 1:3 utilizing the instrument’s on-board dilution feature. The final test results are reported automatically to an electronic medical record. Following the reported incident, an investigation and troubleshooting plan was developed, encompassing the following steps: Repeat patient testing with total bilirubin concentration &amp;gt; 30 mg/dL and &amp;lt;0.1 mg/dL; Rule out the previously reported potential interferences, including Immunoglobin M and acetaminophen; Conduct a 90-day quality control (QC) review; Perform split test analysis on two instruments within the laboratory and at a reference laboratory; Conduct patient chart reviews to identify discrepancies based on previously reported values; Complete a root cause analysis and develop corrective/preventive action plan. Results Patient sample &amp;lt; 0.1 mg/dL was tested on an alternative instrument, resulting &amp;gt; 30 mg/dL. Patient with normal IgM of 161 mg/dL didn’t reveal any other potential drug interferences in chart review. The 3-month QC review found consistent with peer performance. Split comparison of 6 patients revealed discrepancies for samples &amp;gt; 30 mg/dL on one of the two instrument units. When total bilirubin &amp;gt; 30 mg/dL, the malfunctioning unit erroneously reported values &amp;lt; 0.1 mg/dL after dilution. Review of 34 patient charts showed the impact dates were spanned for 39 days. Since the on-board dilution feature is utilized by 10 other analytes, 892 diluted samples were analyzed for discrepancies. 36 discrepant results were identified among 4 affected assays including total bilirubin, direct bilirubin, creatine kinase, and alanine aminotransferase. These results were corrected, and providers were notified. Conclusions The root cause was traced to a malfunction in one instrument unit, despite no malfunction flags. The laboratory QC concentrations fell within the analytical measurement range, missing the dilution issue during the daily QCs. During an extensive repair period, the on-board dilution was disabled on the affected unit and samples were re-routed to alternative instrument for testing. Policy changes and operator training were initiated for a new result verification process, impacting the laboratory productivity. Autoverification of diluted sample results was disabled for all chemistry analyzers. The vendor identified the issue as sample transfer unit crane misalignment in the up/down direction. It is worth noting that proficiency testing or QCs often do not extend beyond the analytical measurement ranges, leading to undetected incidents. Additional quality measures like periodic patient chart reviews, patient sample comparisons, and other quality assurance tools can aid in on-going dilution performance verification. Open communication between the physicians and laboratories is crucial for prompt issue identification and resolution.

B-105 Farr Radioimmunoprecipitation Method Enhances Serial Monitoring of Quantitative Anti-dsDNA (double-stranded) Antibody Measurements in Lupus

Abstract Background Anti-double stranded DNA (anti-dsDNA) antibodies are an important criterion in the diagnosis, classification, and management of systemic lupus erythematous (SLE). High avidity anti-dsDNA IgG may be more clinically relevant and specific for SLE. As such, radioimmunoassay according to the Farr technique (Farr-RIPA) is often considered more sensitive and quantitative than enzyme-linked immunosorbent assay (ELISA) and Crithidia luciliae immunofluorescence assay (CLIFT) methods. Methods Measurements of anti-dsDNA antibodies in 147,016 serum patient samples were obtained by lab-developed Farr-RIPA. Serum with endogenous antibodies binds to 125I-radiolabelled dsDNA and undergoes subsequent immunoprecipitation under high salt conditions which selects for highly avidity anti-dsDNA antibodies. The analytic measurement range (AMR) of the assay is 5.7 to 85 IU/mL, and dilutional linearity is validated to 68,000 IU/mL for results &amp;gt;85 (ULOQ). Inter-assay precision is &amp;lt;10% CV. Results Of 147,016 measured samples, 5.4% (7800) were positive for anti-ds DNA antibodies (mean 251.7) with numeric values, ranging from 8.0 to 55,399 IU/mL. The numeric distribution of all positive results was such that 76% (5859/7800) were between 8.0 - 60 IU/mL, and the median was 19.4 with an interquartile range (IQR) of 36.1. A small percentage (3.9%) had very high anti-dsDNA levels greater than 1000 IU/mL and 0.4% (35/7800) were greater than 10,000 IU/mL. Serial measurements comprised almost half (45.5%) of all positives, occurring in 1016 unique patients an average of 3.5 levels within a 2-year time frame. A fifth of those patients, 200, were more frequently monitored with at least 4 levels. Of patients with the very highest dsDNA (&amp;gt;10,000), we analyzed the results of 17 unique patients who were frequently monitored an average of 6.1 times. Peak and nadir values yielded a mean delta of 20,751 with a mean of 264 days elapsing between peak and nadir. All except one showed a marked decrease in Anti-dsDNA over time with an average decrease of 15,685 IU/mL. Conclusions Here, we performed 147,016 Anti-dsDNA antibody measurements by Farr-RIPA, a precise method with a broad analytic range as compared to other methods which have a limited upper limit of quantitation or are semi-quantitative. Our 7800 positive Farr-RIPA results exhibited quantitative results from 8.0 to 55,399 IU/mL. The median of 19.4 and IQR of 36.1 showed most results to be &amp;lt;55.5 IU/mL. Very high levels &amp;gt;300 and &amp;gt;1000 IU/mL were seen in 10% and 4% of patient samples, respectively. Serial monitoring was frequent. In patients with the very highest levels &amp;gt;10,000, an-eight fold decrease in peak Anti-dsDNA levels was achieved over a mean of 264 days with more than half (9/17) achieving levels &amp;lt;250. The ability to detect and meaningfully monitor these patients is enhanced by the Farr-RIPA method. In conclusion, in 7800 positive samples, we demonstrated a wide range of inter- and intra-patient numeric Anti-dsDNA concentrations that denote the clinical usefulness of serial monitoring by Farr-RIPA.

B-120 Reference Interval (RI) Estimation for Pediatric Magnesium using an Indirect Method with Unsupervised Machine Learning Tool and Programming Language

Abstract Background Magnesium is an important intracellular component present in all enzymatic reactions involving Adenosine Triphosphate (ATP) utilization, with the majority stored in bones. In the blood, it exists as a free fraction and another bound to proteins. Regulation occurs through renal processes, and for this reason, hypermagnesemia is associated with renal insufficiency, compromising the central nervous system. On the other hand, hypomagnesemia cases are related to pancreatitis, intestinal malabsorption, childhood malnutrition, among other factors. Following complaints from pediatric doctors that our reference intervals (RI), as suggested by the manufacturer, would yield falsely elevated results in healthy patients, we estimated a new RI in the population served Methods We employed data mining followed by estimation using an indirect method through the LabRI™ algorithm with parametric, non-parametric, and robust statistical treatments for outlier exclusion, implemented in the R language. Latent abnormal values of outpatient pediatric patients were considered. We defined three pediatric partitions for both sexes, aged 0 to 6 years, 7 to 12 years, and above 12 years, using the comparative RI described by the Roche manufacturer. Data were extracted from our Data Lake between January and December 2022 in the Federal District of Brazil, from a laboratory part of a large network. Exclusion criteria included: Potassium &amp;gt; 5.5 and &amp;lt; 3.0 mmol/L; Phosphorus &amp;gt; 8.0 and &amp;lt; 1.5 mg/dL; Total Calcium &amp;gt; 12 mg/dL and &amp;lt; 7 mg/dL; Ionized Calcium &amp;gt; 1.5 mmol/L and &amp;lt; 0.8 mmol/L; Creatinine &amp;gt; 2.0 mg/dL; C-reactive protein (CRP) &amp;gt; 10 mg/dL; Ferritin &amp;gt; 700 ng/mL; A1C &amp;gt; 7.0%; LDL Cholesterol &amp;gt; 200 mg/dL; Magnesium repeated within &amp;lt; 12 months, and samples of hospital origin. Results The evaluated population after exclusion criteria totaled 6,865 children, distributed as follows: 26.0% aged 0 to 6 years, 30.3% aged 7 to 12 years, and 43.7% above 12 years. Outliers were excluded in 1.5%, 0.9%, and 1.0%, respectively. In all partitions, there was a significant discrepancy compared to the reference intervals recommended by Roche. In our estimation, there was an expansion of the upper limit of the reference interval in all partitions, supporting the clinical opinion. The new reference intervals became: 0-6 yrs: from 1.7-2.3 to 2.0-2.7; 7-12 yrs: from 1.7-2.1 to 2.0-2.6; and &amp;gt;12 yrs: from 1.7-2.2 to 1.9-2.6. The standard deviation varied between 0.19 and 0.20, and the median between 2.20 and 2.32 Conclusions The manufacturer states in the package insert that they did not assess the RI for the pediatric population and that each laboratory should verify the RI in the population served. We approve the adoption of the estimated RI for the pediatric population calculated by the LabRI™ tool in the partitions of 0-6 years, 7-12 years, and &amp;gt;12 years, stating in the report “Reference interval established by an indirect method in 6865 children tested in the laboratory, partitioned by age group.”

A-071 Macroprolactin Screening in Patients with Hyperprolactinemia: Comparison Between Different Criteria for Defining Macroprolactinemia

Abstract Background Prolactin (PRL) exists in different forms in human serum. The predominant form is monomeric PRL, the other forms include dimeric PRL and polymeric PRL, also known as macroprolactin, a biologically inactive form. Macroprolactin can be measured by almost all immunoassays for PRL. This may lead to misdiagnosis and mismanagement of patients. Polyethylene glycol (PEG) precipitation is the most widely used method for detecting macroprolactin, generally employing a cutoff of 40% to distinguish macroprolactinemia from true hyperprolactinemia. This approach lacks specificity, so the reported result may be misinterpreted in cases in which excess macroprolactin occurs simultaneously with supraphysiological concentrations of monomeric prolactin. Nowadays, it is recommended to report results as post-PEG PRL using method-specific post-PEG reference intervals, classifying as macroprolactinemia (false or pseudohyperprolactinemia) those individuals with post- PEG PRL within post-PEG reference intervals and true hyperprolactinemia above the upper limit of the post-PEG reference interval. The objective of this study was to evaluate the prevalence of macroprolactinemia in patients with hyperprolactinemia using two different criteria, a cutoff &amp;lt; 40% in PEG precipitation and a post- PEG PRL within post-PEG assay specific reference range. Methods We analyzed blood samples requesting serum macroprolactin from patients admitted to a private reference clinical laboratory in Rio de Janeiro, Brazil, from 01/01/2019 to 12/31/2023. Anonymized data on laboratory tests was available from a database of the local Laboratory Information System. All patients included had PRL levels above the reference range, males &amp;gt;15.2 ng/mL, females &amp;gt;23.3 ng/mL (ECLIA, Modular, Roche). Results 9423 patients, 80.1% women (W) were evaluated. Men (M) were statistically significantly older than women (p&amp;lt;0.001) (45.6; SD=15.0 vs. 38.9; SD=11.5). Prolactin median levels were significantly higher in women (p&amp;lt;0.001) than men (37.4ng/mL, IQR=26 vs. 23.8ng/mL, IQR=17.1). Macroprolactinemia detection was greater (p&amp;lt;0.001) by post-peg PRL concentration criteria (9.7% - 10.1%W vs. 8.4%M), than by &amp;lt; 40% PRL recovery criteria (5.5% - 5.7%W vs. 4.8%M). Dividing patients by prolactin levels (&amp;lt;50.0; 50.0 to &amp;lt;100.0; 100.0 to &amp;lt;150.0, &amp;gt;150.0 ng/mL, we found macroprolactinemia in 5.2% (5.2%W vs. 5.2%M), 7.7% (8.2%W vs. 2.4%M), 2.8% (2.8%W vs. 2.5%M) and 1.6% (1.3%W vs. 2.6%M) - &amp;lt;40% PRL recovery criteria; and 12.1% (12.8%W vs. 9.8%M), 4.4% (4.8%W vs. 0.6%M), 0.8% (0.8%W vs. 0%M), 0.0% (0%W vs. 0%M) - post-PEG PRL concentration criteria. By the last criteria, no patient with total PRL more than 150 ng/mL had macroprolactinemia. Conclusions The criterion for defining macroprolactinemia has a big impact on the study results and needs to be considered in data interpretation and comparison with other studies. PEG precipitation is an easy and fast screening method for macroprolactin. Its main purpose should be determining whether the bioactive monomeric prolactin concentration is increased which is why the post-PEG PRL with corresponding reference interval is the most suitable way of reporting results.

Efficient representations of upper limits and confidence intervals for experimental data

Upper limits and confidence intervals are a convenient way to present experimental results. With modern experiments producing more and more data, it is often necessary to reduce the volume of the results for convenient distribution. A common approach is to take a maximum over a set of upper limits, which yields an upper limit valid for the entire set. This, however, can result in significant sensitivity loss, because we discard more constraining data. In this paper, we introduce upper limits and confidence intervals that allow one to summarize results with a small relaxation of constraints. A toy example and an application to upper limits in all-sky continuous gravitational wave searches are worked out. Published by the American Physical Society 2024