EDTA Plasma Research Articles

VE-cadherin shedding in vitro and in patients with aortic aneurysm and dissection

VE-cadherin (VEC) is a major endothelial adhesion protein, which controls vascular homeostasis. During vascular diseases, VEC can be shed from the endothelial surface by proteases like ADAM10/17, which cleave the extracellular domain of VEC in response to inflammatory cytokines like TNF-α. The resulting, soluble fragments (sVEC) are discussed as a potential marker for endothelial barrier breakdown. However, its pathologic role or its potential as a specific biomarker for aortic diseases is yet unknown. Here we investigated the specificity and linkage of sVEC production with ADAM10/17 and TNF-α, both in vitro and in patients with aortic aneurysms and dissections, comparing the findings with those from patients with carotid stenosis and varicosis. Thereby, the baseline levels of sVEC, TNF-α, ADAM10 and Albumin was measured in clinical plasma samples and cell culture supernatants of human aortic endothelial cells (HAOEC) treated with TNF-α or ADAM10/17 inhibitors. The integrity of HAOEC monolayers was tested by permeability assays using Alexa488-conjugated dextran (10 kDa). Peripheral EDTA plasma samples taken preoperatively from patients ≥ 18 years of age that were diagnosed for aortic dissection (n = 29), aortic aneurysm (n = 76), carotid stenosis (n = 29) and varicose veins (n = 24) were included. In vitro shedding of VEC was induced by TNF-α and depends on ADAM10/17, which led to altered endothelial permeability. Absolute plasma sVEC levels in patients with aortic dissection (3016 ± 1008 ng/mL) and aneurysm (3288 ± 1376 ng/mL) were not statistically significantly different from patients with carotid stenosis (3013 ± 687.6 ng/mL) and varicose veins (3313 ± 1337 ng/mL). Plasma sVEC levels correlated positively with plasma TNF-α (r = 0.5586, p < 0.0001) and ADAM10 (r = 0.7003, p < 0.0001) levels with the highest degree of correlation between ADAM10 and sVEC for chronic aortic dissection (r = 0.7890, p = 0.0013), reflecting TNF-α and ADAM10 dependency of VEC shedding. In summary, VEC shedding and (plasma) sVEC levels are influenced by TNF-α and ADAM10/17 and could play a relevant role in the specific pathophysiological context of aortic diseases.

Analytical interference of Burosumab therapy on intact fibroblast growth factor 23 (iFGF23) measurements using an immunoassay: preliminary evaluation

ABSTRACT Our study evaluated the possible interference of Burosumab (human recombinant monoclonal antibody directed against N-terminal domain of FGF23) on the immunoassay of intact FGF23 (iFGF23) with the Liaison XL. The analytical method uses three different antibodies, one of which directed against the N-terminal portion of FGF23. The evaluation of the method accuracy involved the fully automated execution of a dilution test on EDTA plasma from 5 subjects who had not received any monoclonal antibody (mAb), 20 EDTA plasma from patients treated with Burosumab, and 2 EDTA plasma from subjects who had not received any mAb in witch an adequate volume of Burosumab had been added in vitro. One sample with specific diluent (LIAISON® FGF 23) with an adequate volume of Burosumab had been added in vitro. The dilution assay provided highly inaccurate iFGF23 results in samples with therapeutic concentrations of Burosumab and in samples with concentrations below the LoQ (6.5 pg/mL). The addition of Burosumab to the diluent did not produce any analytical interference. Dissociation of iFGF23 from the mAb-target complex in diluted sample could explain the loss of accuracy in the iFGF23 immunoassay using the Liaison XL analyzer. Burosumab could be an interferent in immunoassay procedures of iFGF23.

Protein signatures associated with methylation patterns of heart failure phenotypes

Abstract Introduction The heart failure (HF) syndrome is highly susceptible to the exposome. The interplay between DNA methylation (DNAm), surrogate for exposomal influences, and the plasma proteome in the progression and development of phenotypes of heart failure is unclear. We investigated the relation between methylation patterns of HF phenotypes and proteins signatures. Methods Individuals with symptomatic HF (stage C/D with HFpEF, HFmrEF and HFrEF) of the MyoVasc cohort (N=3,289) were investigated. EDTA-Plasma and DNA were extracted from peripheral blood and stored in -80°C. DNAm was measured using the Infinium MethylationEPIC v2.0 methylation array. Concentrations for 538 proteins were measured using an immuno-qPCR assay in EDTA plasma. Multivariable regression models adjusted for age and sex were used to assess the relationship between DNAm signatures and individual proteins in each phenotype. Ridge-regularized linear regression was used to generate a phenotype-specific protein-signature in relation to each methylation signature, linear regression to estimate links between protein signatures and cardiovascular traits and Cox regression relate protein signatures to clinical outcome. Results Data from 1,317 individuals with symptomatic HF were analyzed. After FDR adjustment, 310 proteins were significantly related to HFpEF methylation signature, 314 to HFmrEF and 266 to HFrEF. Of associated proteins, 49.9% (198) were found in all phenotypes, 8.82% (35) only in HFpEF, 12.1% (48) in HFmrEF and 4.79% (19) in HFrEF. Tumor necrosis, arterial hypertension and T-cell regulation pathways were enriched in all three phenotypes. NT-proBNP had the strongest association with HFrEF (β=0.95 [0.82-1.08], p&amp;lt;0.0001) followed by presence of plaques in carotid artery and C-reactive protein, while left ventricular mass (LVM) had stronger association with HFpEF (β=0.22 [0.11-0.33], p=0.0001). All three signatures were associated with worsening of HF (HFpEF: HR=1.93 [1.61-2.30], p&amp;lt;0.0001; HFmrEF: HR=1.63 [1.29-2.04], p&amp;lt;0.0001; HFrEF: HR=1.64 [1.38-1.95], p&amp;lt;0.0001) and all-cause death in HF (HFpEF: HR=1.93 [1.65-2.26], p&amp;lt;0.0001; HFmrEF: HR=1.95 [1.58-2.42], p&amp;lt;0.0001; HFrEF: HR=2.24 [1.86-2.69], p&amp;lt;0.0001). Methylation-associated protein signatures had stronger associations with clinical outcome than the methylation signatures themselves (p &amp;lt; 0.01). Conclusion This study revealed protein signatures associated with methylation patterns of HF phenotypes that shared common and unique features for HF phenotypes. Important common pathways were enriched in tumour necrosis, arterial hypertension and regulation of T cells. However, important differences between phenotypes were also revealed, e.g. NT-proBNP was strongly associated with the HFrEF protein signature and LVM with the HFpEF signature. The methylation-associated protein signatures emphasise the possible exposomal influence on HF syndrome.

Comparison of multiple high sensitivity cardiac troponin assays for early low risk rule out of myocardial infarction: SCORECARD

Abstract Background/Introduction The use of a single low high-sensitivity cardiac troponin measurement to rule out myocardial infarction (MI) at presentation is advocated by international guidelines. Studies have not systematically compared high-sensitivity cardiac troponin (hs-cTn) I and T assays to determine which values should be used to rule out MI in patients with suspected acute coronary syndrome. Methods In a pooled analysis from three prospective observational cohort studies the lowest cTn concentration was determined that gave a negative predictive value (NPV) of ≥99.5% for MI or death at 30 days on presentation to the emergency department. EDTA or lithium heparin plasma or serum samples collected at presentation were measured using five hs-cTnI assays (Abbott ARCHITECT i2000, Beckman Coulter Access 2, Siemens Atellica IM, Ortho-Clinical Diagnostics VITROS 5600, LSI Medience PATHFAST) and one hs-cTnT assay (Roche Cobas e411). The diagnostic outcome of MI or death at 30 days was adjudicated according to the Fourth Universal Definition of MI. Optimal thresholds were determined to identify the highest proportion of patients that could be considered for discharge for a NPV of ≥99.5% for each assay. Results Among 941 patients, MI or death at 30 days occurred in 113 (12%). Optimized thresholds varied between assays ranging from &amp;lt;2 to &amp;lt;7 ng/L (Table) that identified between 22% and 60% of patients as low risk (0-1%) for MI or death at 30 days. Conclusions Our data identify differences in the effectiveness of thresholds between hs-cTnI and hs-cTnT assays for the same safety performance to rule out MI on presentation using a single measurement. In some cases, these thresholds differ from those used in clinical practice. Due to lack of assay standardization, optimal decision thresholds should be defined and validated for each high sensitivity cTn assay.

Associations of omega-3 fatty acid subclasses with cardiovascular diseases in 500,000 individuals

Abstract Increased blood levels of omega-3 fatty acids have consistently been shown to be associated with reduced risk of cardiovascular diseases (CVD). However, large scale placebo-controlled trials of omega-3 supplementation have had discordant results: in 2018 REDUCE-IT reported a 25% risk reduction, whereas in 2020 STRENGTH reported no risk reduction. The two trials had both different placebos (mineral vs corn oil) and omega-3 formulations (EPA vs DHA+EPA). There is not yet a consensus on what explains these results. Here we describe the profiling of omega-3 fatty acid subclasses, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) with nuclear magnetic resonance (NMR), and test their associations with incident CVD in 500,000 individuals from UK Biobank. We utilized 500 MHz NMR spectrometers to analyze total omega-3 and its subclasses in EDTA plasma samples and employed biomarker-specific quantification algorithms to measure their absolute concentrations. In this study, we developed a novel algorithm to quantify EPA, complementing previously described algorithms for omega-3 and DHA. Correlation (r^2) of this novel NMR-based quantification and gas chromatography-based measurements was 0.77 for EPA. On average, DHA comprised 44.5% of the total omega-3 concentration, EPA accounted for 22.2%, and other subclasses constituted 34.3% in the cohort. We computed age and sex adjusted associations of omega-3, DHA, and EPA with 10-year risk of CVD among individuals who were not taking cholesterol lowering medication. We discovered protective associations: for DHA a hazard ratio of 0.85 (0.86-0.89, 95% confidence interval) per standard deviation versus 0.96 (0.95-0.98) for EPA, and 0.95 (0.93-0.97) for total omega-3 (Figure). Since DHA (used in the STRENGTH trial with a null result) has a significantly stronger epidemiological association than EPA, these results from a large-scale observational study do not support the hypothesis that the differential use of DHA and EPA in the REDUCE-IT and STRENGTH trials explains their divergent results.Figure

Deciphering lipoprotein(a) atherogenicity with use of high-throughput proteomics

Abstract Background Accumulating observational and genetic evidence suggests that lipoprotein(a) [Lp(a)], is significantly more atherogenic than other apolipoprotein-B containing particles. Systemic inflammation is thought to mediate the atherogenic effects of Lp(a). Previous studies have predominantly focused on single inflammatory biomarkers, an approach that fails to capture the broader molecular response to elevated Lp(a) levels. Purpose The aim of this study was to derive a proteome-wide signature of plasma Lp(a) concentrations and subsequently identify the pathways through which Lp(a) influences the risk of coronary artery disease (CAD). Methods This study included 41,123 UK Biobank participants with baseline Lp(a) measurements who also underwent a proteomic assessment. Relative concentration of 2,920 proteins was quantified in EDTA plasma samples using a high-throughput proximity extension assay. Lp(a)-associated proteins were identified in linear regression models, adjusting for age, sex, body mass index, race, smoking status, estimated glomerular filtration rate, medication use, and apolipoprotein B. Proteins linked with Lp(a) concentration were then evaluated for their association with incident CAD risk using Cox proportional hazards models. Significant traits were further included in pathway enrichment analysis. Results Out of 2,920 analyzed proteins (Figure 1), 140 showed a positive association with Lp(a) concentration, while 336 exhibited a negative association after adjustment for multiple testing (False discovery rate &amp;lt; 0.05). The strongest positive associations were observed for apolipoprotein F, group 10 secretory phospholipase A, and C4b-binding protein beta chain. The strongest negative associations were observed for asporin, aminoacylase-1, and retinol-binding protein 5. Among 140 proteins positively associated with Lp(a), 49 were associated with an increased risk of CAD. Conversely, among the 336 proteins negatively associated with Lp(a), 10 were associated with a decreased risk of CAD. Pathway enrichment analysis (Figure 2) indicated that proteins linked with both Lp(a) levels and CAD risk predominantly upregulated pathways related to peptide-ligand receptor signalling, platelet degranulation, neutrophil degranulation, and cytosolic calcium response. Conversely, pathways related to HDL remodeling, PI3K/AKT, KIT, and nuclear receptor signalling were downregulated. Conclusions The greater atherogenic potential of Lp(a) may be attributable to the modulation of several molecular pathways, particularly those involving platelet and neutrophil responses, cell signalling, and lipoprotein metabolism.

Discrepancies of bovine haptoglobin concentrations between serum and plasma using two different anticoagulants and a colorimetric assay based on peroxidase activity.

Haptoglobin (Hp) is an emerging diagnostic marker in cattle, and knowledge of suitable sample types and measurement methods is important. The aims of this study were to compare the results of a colorimetric assay (CA) and an ELISA for bovine Hp using serum, EDTA plasma, and lithium-heparinized (LH) plasma, respectively, and to assess the diagnostic potential for puerperal metritis. In experiment 1, Hp was measured in pooled aliquots of serum (n = 10), EDTA plasma (n = 10), and LH plasma (n = 10) of 100 healthy fresh lactating dairy cows from 10 farms using both the CA and the ELISA. In experiment 2, five healthy and five cows with acute puerperal metritis were sampled, and Hp was determined using both assays for all three sample types. In experiment 3, aliquots of serum and LH plasma from cows in different lactation stages were transferred into plain, EDTA-coated, and LH-coated tubes and mixed before colorimetric analyses. Distilled water was also placed into each tube type and treated similarly. Plasma samples measured with the CA showed on average 2.3 (EDTA) and 2.5 (LH) times higher Hp concentrations compared with serum, whereas no differences were seen with the ELISA results between sample types. Based on a clinical cut-off value, both methods differentiated sick from healthy cows. Haptoglobin measurements with the ELISA were less precise compared with CA measurements due to high dilutions. No influence of the anticoagulants on the CA was observed. Due to measurement discrepancies between serum and plasma, CAs for bovine Hp based on peroxidase activity should be performed with serum, or specific reference ranges for plasma samples should be established. In this study, CA results obtained with LH plasma were more precise than results obtained with EDTA plasma. Both the CA and the ELISA are suitable diagnostic tools for the diagnosis of puerperal metritis, but CA measurements were more precise in this study.

Effects of Angiotensin-I-Converting Enzyme (ACE) Mutations Associated with Alzheimer's Disease on Blood ACE Phenotype.

Our recent analysis of 1200+ existing missense ACE mutations revealed that 400+ mutations are damaging and led us to hypothesize that carriers of heterozygous loss-of-function (LoF) ACE mutations (which result in low ACE levels) could be at risk for the development of late-onset Alzheimer's disease (AD). Here, we quantified blood ACE levels in EDTA plasma from 41 subjects with 10 different heterozygous ACE mutations, as well as 33 controls, and estimated the effect of these mutations on ACE phenotype using a set of mAbs to ACE and two ACE substrates. We found that relatively frequent (~1%) AD-associated ACE mutations in the N domain of ACE, Y215C, and G325R are truly damaging and likely transport-deficient, with the ACE levels in plasma at only ~50% of controls. Another AD-associated ACE mutation, R1250Q, in the cytoplasmic tail, did not cause a decrease in ACE and likely did not affect surface ACE expression. We have also developed a method to identify patients with anti-catalytic mutations in the N domain. These mutations may result in reduced degradation of amyloid beta peptide Aβ42, an important component for amyloid deposition. Consequently, these could pose a risk factor for the development of AD. Therefore, a systematic analysis of blood ACE levels in patients with all ACE mutations has the potential to identify individuals at an increased risk of late-onset AD. These individuals may benefit from future preventive or therapeutic interventions involving a combination of chemical and pharmacological chaperones, as well as proteasome inhibitors, aiming to enhance ACE protein traffic. This approach has been previously demonstrated in our cell model of the transport-deficient ACE mutation Q1069R.

A-020 Evaluation of the QuidelOrtho Diagnostics Vitros NT-proBNP II Assay

Abstract 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 &amp;lt;=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 (&amp;gt;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-123 Comparative Assessment of Unmanned High-Speed Aerial Vehicles in Medical Logistics: Blood Sample Transportation Amidst Weather Variability

Abstract Background Drones, as an innovative technology, hold transformative potential in the field of medical logistics, especially in the transportation of sensitive medical materials like blood samples. This study aimed to assess and compare the impact of high-speed drone transportation with conventional car transportation on the integrity and preanalytics of blood samples, taking into account various blood materials and analytes. Methods Blood samples, including EDTA whole blood, serum, and plasma anticoagulated with Citrate and Lithium-Heparin transported as whole blood, were subjected to transportation via both drone and car. Drone flights were tested under diverse weather conditions (ranging between 4 and 20 degrees Celsius), and results were compared to samples stored without transportation. The maximum drone speed exceeded 100 km/h. A total of 28 analytes were tested on Serum, 20 on EDTA, 26 on Lithium-Heparin, and 5 on Citrate blood. Statistical analyses were performed using Passing Bablok and Bland-Altman methods. Results For Serum samples, the correlation coefficient (r) ranged from 0.830 to 1.000, and slopes varied from 0.913 to 1.111. Five analytes (total bilirubin, Calcium, Ferritin, Kalium, and Sodium) exhibited discrepancies between the negative control and the transported sample, with r lower than 0.800, slopes not between 0.8 and 1.2, and mean (%) not between +/- 10%. However, no significant differences were noted between drone and car transportation. Similar patterns emerged for EDTA, Lithium-Heparin, and Citrate samples, with r ranging from 0.829 to 0.997, 0.939 to 0.998, and 0.830 to 1.000, respectively. Slopes ranged from 0.956 to 1.051, 0.938 to 1.085, and 0.913 to 1.111. Despite identifying a few discrepancies in specific analytes, no significant differences were observed between transportation methods. Conclusions n comparison to transportation by car, drone transportation of blood samples did not lead to alterations in concentrations of commonly used analytes. Notably, instances of differences before and after transportation were attributed to the transportation process itself rather than the mode of transportation. This suggests that the use of drones for medical sample transport can be deemed comparable to, if not superior to, traditional car transportation methods.

B-015 Analytical Verification of MR-proADM Biomarker in Human EDTA Plasma on Immunoassay Analyzer LIAISON® XL of Diasorin

Abstract Background Adrenomedullin (ADM) is a potent vasodilator peptide of 52-aminoacid belonging to the calcitonin family of peptides. Midregional pro-ADM (MR-ProADM) is a precursor for ADM that circulates is in a 1:1 ratio with it, and proportionally represents its levels and activity. Increased ADM circulating concentrations have been described for several disease states, including dysfunction of the cardiovascular system and sepsis. However, reliable ADM quantification has been hampered by the short half-life, the existence of a binding protein, and its physical properties. Hence, quantificacion of MR-proADM represents a more suitable option. The biomarker MR-proADM has been shown to be an accurate prognostic marker for outcome prediction in patients with lower respiratory infections, sepsis, urinary tract infections, and kidney disease. The objective of this study was the verification of the metrological characteristics and the verification of the linearity of quantitative measurement range, as declared by the manufacturer, of the LIAISON® Brahms MR-proADMTM on Liaison® XL (DiaSorin). Methods The verification was performed with two levels of quality controls (QC) from the manufacturer (x̄L=1,19 nmol/L and x̄H=5,48 nmol/L), and residual EDTA plasma samples from patients with an active sepsis code. The evaluation included the assessment of: • Detection capability (including limit of quantification (LoQ) and limit of detection (LoD), measuring three samples at the manufacturer's stated concentration (0.21 nmol/L and 0.09 nmol/L, respectively) in duplicate within 4 runs). • Precision (CV, %) and accuracy (bias, %) within, measuring 10 replicates of each QC level; and between run, measuring 5 replicates for each QC level within 5 runs. • Linearity of the quantitative range of measurement (six intermediate samples prepared by mixing a high concentration sample- XH=9.64 nmol/L- and a low concentration sample, XL=0.59 nmol/L; measured in triplicate). All studies were performed in accordance with the recommendations of the Clinical Laboratory Standards Institute guidelines. Statistical analysis was performed using Microsoft Excel®, 2016. Results All results with diluted samples presented a signal (RLU) higher than that detected in samples without analyte, so the LoD was verified. The precision at the LoQ concentration was 26.7% (acceptance criteria was set as &amp;lt;20%). CV for within-run precision were 4.3% and 2.0% and for between-run precision 6.8% and 7.9% for low (L1) and high (L2) control level, respectively. The average bias was 3.60% for L1 and 4.23% for L2, meeting acceptance criteria (&amp;lt;8%). Linearity was confirmed between 0.59 and 9.64 nmol/L (R2 = 0.995). The biases between the expected and the obtained value were ≤7% through the quantitative range of measurement, except for the lowest concentration sample (close to the quantitation limit). Conclusions Our study showed good compliance with the metrological characteristics declared by the manufacturer for LoD, precision, bias and linearity range. Although the LoQ was not verified, it is outside the clinical decision value in septic patients (&amp;lt; 2.25 nmol/L) and it is not deemed a limitation for clinical practice. Additionally, the Liaison XL® platform permits us to configure an emergency protocol circuit (24/7) with a TAT of 35 min.

A-011 Single High-Sensitivity Cardiac Troponin I Compared to High-Sensitivity Cardiac Troponin T Measurement to Rule Out Acute Myocardial Infarction at Low Risk for 30-Day Adverse Events: CONTRAST Study

Abstract Background Cardiac troponin (cTn) is the preferred biomarker for diagnosing myocardial injury and acute myocardial infarction (MI). There are few comparative studies addressing the clinical performance of high-sensitivity (hs)-cTnI and hs-cTnT assays using fresh plasma for early rule out of myocardial infarction (MI) on presentation in patients presenting to emergency departments (ED). This study examined the performance strategies of a derived optimal concentration for a single high-sensitivity cardiac troponin I (hs-cTnI) measurement compared to a derived optimal concentration for a single high-sensitivity cardiac troponin T (hs-cTnT) measurement to rule out acute MI. Methods The COmparisoN of high-sensitivity cardiac TRoponin I and T ASsays Trial (CONTRAST) (NCT03214029) is a prospective, observational cohort study of consecutive adult ED patients (n = 2208) undergoing serial cTn measurements as clinically indicated. hs-cTnI (Abbott ARCHITECT) and hs-cTnT (Gen 5, Roche e601) measurements using fresh EDTA plasma were obtained. We determine optimal hs-cTn cutoffs for negative predictive value (NPV) and sensitivity for the diagnosis of acute MI (type 1 and type 2) to allow for a maximum number for early discharges with minimal risk of adverse events (acute MI or cardiac death) at 30 days. Results Acute MI occurred in 161 patients (7.3%), including 68 (42.2%) type 1 MI and 93 (57.7%) type 2 MI. For hs-cTnI (&amp;lt;2 ng/L) optimal NPV and sensitivity for adverse events were 99.1% (95% confidence interval 97.7%-99.8%) and 98.2% (CI. 95.4-99.5%). 450 Patients (21%) qualified for early rule out, at a 1.8% miss rate at 30 days. For hs-cTnT (&amp;lt;6 ng/L) optimal NPV and sensitivity for adverse events were 99.2% (CI 98.0%-99.8%) and 98.1% (CI. 95.3-99.5%). 513 Patients (24%) qualified for early rule out, at a 1.9% miss rate at 30 days. Conclusions In CONTRAST, a strategy using a single sample hs-cTnI or hs-cTnT alone allows for the early identification of patients unlikely to have acute MI and who are at very low risk for adverse events at 30 days. Minor differences existed between the Abbott ARCHITECT hs-cTnI assay and the Roche e601 hs-cTnT (Gen 5) assay in fresh plasma were found.

A-057 Assessing Direct Renin Stability in EDTA Plasma Prior to Separation from Cells and Post-thaw

Abstract Background Renin is an enzyme secreted by the kidneys responsible for blood pressure regulation through the renin-angiotensin-aldosterone axis. Direct renin measurements are frequently used to investigate underlying causes of hypertension, including primary aldosteronism (PA), which is screened for using an aldosterone:renin ratio (ARR). Appropriate handling of renin samples in the preanalytical phase is critical, as cryoactivation of prorenin can occur when samples are refrigerated or cooled for extended periods of time, falsely elevating results. Manufacturer instructions for renin handling are often poorly defined and there is currently no consensus as to best handling practices. Two variables that frequently lead to renin sample rejections in our laboratory are time to centrifugation after collection and time kept at room temperature (RT). The objective of this study was to evaluate the stability of direct renin under ambient and freeze-thaw conditions in an effort to reduce test cancellations due to improper handling. Methods Plasma samples collected from five volunteers with consent in K2EDTA tubes were used for renin stability studies. Baseline renin samples were kept at RT for two hours after collection, centrifuged, measured, and subsequently frozen for post-thaw studies. To assess stability before separation from cells, samples kept at RT for two and four hours prior to centrifugation were assayed in triplicate for direct renin. For post-thaw stability studies, plasma samples were split into two aliquots each and frozen at -20⁰C for at least 24 hours, but no longer than 30 days. After removal from -20⁰C, one set of aliquots was thawed on the benchtop at RT and the second set was thawed in an RT water bath for up to one hour. Samples were centrifuged and assayed for direct renin in triplicate at baseline and six hours post-thaw. Direct renin was measured using the LIAISON XL chemiluminescent immunoassay (Diasorin). Bias was assessed after each treatment. The total allowable error (TEa) was ±2 pg/mL or ±20%. Results Measured renin concentrations ranged from 6.8-29.7 pg/mL. The percent bias in direct renin concentrations when comparing samples stored for two-hour and four-hour timepoints before centrifugation was 2.0% on average. Post-thaw studies comparing renin concentrations at the baseline and six-hour timepoints revealed an average percent bias of 13.1% and 12.2% for RT and water bath thawing methods, respectively. All samples tested were within the TEa. Conclusions Direct renin is stable in lavender K2EDTA tubes at RT for up to four hours, prior to centrifugation and separation from cells. Renin concentrations remained stable after storage at -20⁰C and thawing at RT for up to six hours, regardless of thawing method. By expanding direct renin stability criteria, we hope to reduce the number of cancellations due to preanalytical handling errors and prevent redundant phlebotomy for patients.

B-254 Analytical and Clinical Performance Evaluation of Plasma pTau217 in a Clinical Diagnostic Laboratory

Abstract Background Blood-based biomarkers provide an accessible and cost-effective tool for diagnosing Alzheimer’s disease (AD). Among these biomarkers, phosphorylated tau 217 (pTau217) shows promise for both AD diagnosis and differential diagnosis, as well as for facilitating access to emerging disease-modifying therapies. The ALZpath SIMOA pTau-217 v2 assay is a digital immunoassay designed for quantifying pTau-217 in human EDTA plasma samples. This study assesses the analytical performance of plasma pTau217 assays as a Laboratory Developed Test (LDT) appropriate for diagnostic application. Methods In this analytical study, we evaluate accuracy, precision, detection limits, linearity, and analyte stability. Plasma pTau217 levels were measured using the ALZpath pTau217 v2 assay on a single Quanterix HD-X SIMOA Analyzer platform at BC Neuroimmunology Lab. Inc. Vancouver, British Columbia, Canada. As a clinical testing laboratory, our validation procedures are in accordance with CAP and CLIA requirements, with a primary focus on adhering to CLSI guidelines for both analytical and clinical performance testing. To determine a reference range and cut-off, samples of Amyloid PET-confirmed cases (n=263) and healthy subjects between the ages of 55 and 95, with a roughly equal ratio of males to females (n=219), were tested. Results The ALZpath pTau217 assay demonstrates an analytical measurement range of 0.0046 - 3.4056 ng/L, with a limit of blank (LoB) of 0.0019 ng/L, a limit of detection (LoD) of 0.0046 ng/L, and a limit of quantification (LoQ) of 0.03 ng/L. Linearity spans from 0.06 to 1.75 ng/L, with repeatability showing intra-laboratory precision above LoQ ≤ 20% CV. Stability is maintained at 4⁰C for ≤ 1 week, at room temperature for ≤ 72 hrs, at -20⁰C for ≤ 2 weeks, and at -70⁰C for ≤ 3 weeks, with freeze/thaw cycles tolerated up to 6 times. Moreover, interference is not detected at the maximum concentrations tested for albumin, unconjugated bilirubin, biotin, hemoglobin, creatinine, and heterophilic antibodies. The reference range was determined using the 95% reference interval, resulting in 0.398 ng/L. ROC analysis yielded an AUC of 0.932 with a Youden index of 0.338 ng/L. At the Youden index, sensitivity was 90.0% with a specificity of 85.6%. Specificity reached 95.5% at the upper cut point of 0.471 ng/L, while sensitivity was 94.8% at the lower cut point of 0.242 ng/L. Conclusions The outstanding analytical performance of pTau217 supports its adoption as a reliable screening and diagnostic tool in clinical practice, aiding clinicians in the accurate diagnosis of AD.

A-012 Predictive Value of Baseline Alpha Defensin Level in Patients with Stable Coronary Artery Disease: A Retrospective Single Center Study

Abstract Background Inflammation plays a central role in atherogenesis. The major neutrophilic peptide alpha-defensin is a promising evolving risk factor for atherosclerosis. The aim of the present study was to examine the role of alpha-defensin in predicting future major adverse cardiovascular events (MACE) occurrence in fully revascularized patients with stable coronary artery disease (CAD) under optimal medical therapy. Methods We retrospectively examined the prognostic value of baseline plasma alpha-defensin levels in predicting MACE occurrence in 174 fully revascularized patients for stable CAD. Demographic, clinical, angiographic, and laboratory data were collected from patients' electronic medical records (EMR). Alpha-defensin levels were measured in samples of EDTA plasma using ELISA kit (HyCult Biotechnology). Other Biochemical parameters were analyzed in serum using COBAS-8000 systems (Roche). Results Alpha-defensin levels were 20% higher among demised patients (10,859 pg/ml, IQR [6,920 to 23,320] vs. 9,020 pg/ml, IQR [5,540 to 16,180] pg/ml, P = 0.15). The absolute increase in mortality risk in patients with alpha-defensin levels greater than the median values was 72.5% (P = 0.33). Log-rank analysis proved both recurrent PCI for de novo lesions (14.9% and 2.3%) and the composite of mortality and recurrent PCI for de novo lesions (27.6% vs. 9.2%) were significantly related to alpha-defensin values greater than the median (&amp;gt;9200 pg/ml). Conclusions Baseline plasma alpha-defensin is an independent predictor of mortality and recurrent PCI among patients with stable CAD. Alpha-defensin may evolve as a promising factor in cardiovascular risk assessment beyond traditional risk factors. Targeting alpha-defensin to ameliorate MACE occurrence should be addressed in future studies.

A-050 Reference Intervals for Plasma Concentrations of C-Terminal Telopeptide of Type-I Collagen (CTX) for Greek Adult Population

Abstract 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.

Rapid and sensitive liquid chromatographic–tandem mass spectrometric methods for the quantitation of dolutegravir in human plasma and breast milk

BackgroundDolutegravir (DTG) is part of a first-line antiretroviral therapy (ART) for HIV management in drug-naïve individuals and is recommended for the treatment of HIV during pregnancy. Robust analytical tools to quantify DTG are necessary to support clinical trials that characterize its multi-compartment drug distribution. MethodsPotassium EDTA (K2EDTA) plasma or whole breast milk was spiked with DTG and an isotopically labeled internal standard. Samples were prepared via protein precipitation prior to LC–MS/MS analysis. The assays were validated in accordance with regulatory recommendations. ResultsAnalytical measuring ranges for DTG quantitation in plasma and breast milk were 100–10,000 ng/mL and 0.500 to 1000 ng/mL, respectively. Inter-assay precision and accuracy were 2.73 % to 3.41 % and −10.6 % to −5.37 % for plasma, and 4.24 % to 12.4 % and −5.63 % to 7.49 % for breast milk, respectively. DTG was stable for three freeze–thaw cycles and for at least 72 h at room temperature in matrix (plasma or breast milk). Additionally, whole blood was stable for 24 h at room temperature and 2 h under conditions of extended heat and humidity. Matrix effects for DTG in plasma and breast milk ranged from 101 % to 108 % and 78.2 % to 99.3 %, respectively. Quantitation in remnant plasma samples yielded measurable concentrations within the primary linearity of the assay. ConclusionsMethods to quantify DTG in human plasma and breast milk have been developed and validated. These assays were designed to satisfy all criteria for implementation in clinical and clinical trial settings.

Novel Metabolites Associated with Decreased GFR in Finnish Men: A 12-Year Follow-Up of the METSIM Cohort.

Identification of the individuals having impaired kidney function is essential in preventing the complications of this disease. We measured 1009 metabolites at the baseline study in 10,159 Finnish men of the METSIM cohort and associated the metabolites with an estimated glomerular filtration rate (eGFR). A total of 7090 men participated in the 12-year follow-up study. Non-targeted metabolomics profiling was performed at Metabolon, Inc. (Morrisville, NC, USA) on EDTA plasma samples obtained after overnight fasting. We applied liquid chromatography mass spectrometry (LC-MS/MS) to identify the metabolites (the Metabolon DiscoveryHD4 platform). We performed association analyses between the eGFR and metabolites using linear regression adjusted for confounding factors. We found 108 metabolites significantly associated with a decrease in eGFR, and 28 of them were novel, including 12 amino acids, 8 xenobiotics, 5 lipids, 1 nucleotide, 1 peptide, and 1 partially characterized molecule. The most significant associations were with five amino acids, N-acetylmethionine, N-acetylvaline, gamma-carboxyglutamate, 3-methylglutaryl-carnitine, and pro-line. We identified 28 novel metabolites associated with decreased eGFR in the 12-year follow-up study of the METSIM cohort. These findings provide novel insights into the role of metabolites and metabolic pathways involved in the decline of kidney function.

Improving Specificity for Ovarian Cancer Screening Using a Novel Extracellular Vesicle–Based Blood Test: Performance in a Training and Verification Cohort

The low incidence of ovarian cancer (OC) dictates that any screening strategy needs to be both highly sensitive and highly specific. This study explored the utility of detecting multiple colocalized proteins or glycosylation epitopes on single tumor-associated extracellular vesicles (EVs) from blood. The novel OC Test employs immunoaffinity capture of tumor-associated EVs followed by proximity-ligation qPCR to detect combinations of up to three biomarkers to maximize specificity and measures multiple combinations to maximize sensitivity. A high-grade serous carcinoma (HGSC) case-control training set of EDTA plasma samples from 397 women was used to lock down the test design, the data interpretation algorithm, and the cut-off between cancer and non-cancer. Performance was verified and compared to CA125 in an independent blinded case-control set of serum samples from 390 women (132 controls, 66 HGSC, 83 non-HGSC OC, 109 benign). In the verification study, the OC Test showed a specificity of 97.0% (128/132; 95% CI: 92.4%-99.6%), a HGSC sensitivity of 97.0% (64/66; 95% CI: 87.8%-99.2%), and an AUC of 0.97 (95% CI 0.93-0.99) and also detected 73.5% (61/83; 95% CI: 62.7%-82.6%) of the non-HGSC OC cases. This test exhibited fewer false positives in subjects with benign ovarian tumors, non-ovarian cancers, and inflammatory conditions when compared to CA125. The combined sensitivity and specificity of this new test suggests it may have potential in OC screening.

Performance evaluation of the quantitative assay Adenovirus ELITe MGB® Kit on EDTA-plasma, using the ELITe BeGenius® system

BackgroundAdenovirus infections constitute an important cause of morbidity and mortality after hematopoietic stem cell transplantation. Detection and monitoring of adenovirus in EDTA-plasma by real-time quantitative PCR is a sensitive tool for identification and management of patients at risk of a potentially fatal infection. ObjectivesThe aim of this study was to evaluate the analytical and clinical performance of the quantitative Adenovirus ELITe MGB® Kit (ELITechGroup S.p.A.) using the ELITe BeGenius® (ELITechGroup S.p.A.) system and compare the assay to a laboratory-developed quantitative real-time PCR assay. Study designAnalytical sensitivity of the Adenovirus ELITe MGB® Kit was determined by testing serial dilutions of the WHO standard. Detection of adenovirus serotypes was assessed using a panel of 51 serotypes. Clinical sensitivity and specificity were determined by comparing the Adenovirus ELITe MGB® Kit results with the laboratory-developed assay results of 155 retrospective and prospective EDTA-plasma samples from transplant recipients. ResultsThe analytical sensitivity of the Adenovirus ELITe MGB® Kit was at least 54 (1.7 Log) IU/mL and the quantitative results showed a high correlation with the WHO standard (R2 = 0.9978; Pearson) within the range of 1.7 to 6.6 Log IU/mL. All 51 adenovirus serotypes were detected. The clinical specificity and sensitivity for EDTA plasma of the Adenovirus ELITe MGB® Kit were 97.4 % and 99.1 % respectively. ConclusionThe Adenovirus ELITe MGB® Kit performed on the ELITe BeGenius® system is a highly sensitive and specific assay for the detection of adenovirus in EDTA-plasma from transplantation patients.