Residual Plasma Samples Research Articles

Longitudinal clinical performance of a novel tumor-naive minimal residual disease assay in patients with resected stage II and III colorectal cancer: A subset analysis from the GALAXY study in CIRCULATE-Japan.

3618 Background: The presence of circulating tumor DNA (ctDNA) can identify patients (pts) at higher risk of recurrence. Longitudinal surveillance of ctDNA may enable early identification of pts who are likely to relapse and presents a window of opportunity for early interventions to improve outcomes. A tumor-naïve plasma-only approach for minimal residual disease (MRD) assessment accelerates turnaround time, enabling rapid adjuvant chemotherapy (ACT) treatment decisions and ongoing molecular surveillance. Methods: Samples were collected from GALAXY in CIRCULATE-Japan and analyzed for postsurgical ctDNA detection at a landmark time point (LMT), 4 weeks after surgery in pathological stage II or III colorectal cancer (CRC). Initially, 80 pts meeting pre-specified eligibility criteria were randomly selected, with enrichment for recurrence to 50% while maintaining the stage II:III recurrent (R)/nonrecurrent (NR) ratio observed in GALAXY. Of those, 23 pts also had longitudinal plasma samples analyzed to date (including 17 false negative (FN) at LMT). Residual plasma samples were analyzed with the Tempus xM MRD assay (xM), a tumor-naïve MRD ctDNA assay that integrates methylation and genomic variant data to deliver a binary MRD call blinded to clinical outcomes. The methylation workflow detects fragments with CRC methylation signatures in differentially methylated regions. The variant classifier detects highly prevalent CRC variants. Longitudinal MRD+ status was defined as any MRD+ call after surgery or ACT; lead time as the time from first MRD+ call after definitive therapy to clinical recurrence. Results: Of the 80 pts, 70 [Stage II n= 29 (41%), Stage III n= 41 (59%)] were evaluable (36 R and 34 NR). At the LMT and with at least 1-year follow-up, 18/36 R pts had detectable ctDNA (MRD+) and 30/34 NR pts had undetectable ctDNA (MRD-), providing clinical sensitivity (CS) of 50% and specificity of 88%. Additional sensitivity analysis included 2 false positive pts who cleared ctDNA with ACT and provided CS 53% and specificity 94% at LMT. Longitudinal analysis of all FNs and ACT treated true positive (TP) pts improved CS from 50% at LMT to 90.9% (stage II 91.7%, stage III 90.5%) on surveillance. The mean lead time was 4.72 mos overall, 5.29 mos for pts treated with surgery alone. Additionally, xM MRD status at LMT strongly correlated with disease-free survival (DFS) with a hazard ratio (HR) of 5.09, superior to 12 week carcinoembryonic antigen (CEA) correlation with DFS, HR 2.63. Conclusions: xM is a novel tumor-naïve MRD assay that demonstrated remarkable clinical longitudinal performance, and can accurately predict clinical recurrence on surveillance. xM ctDNA status was a strong prognostic biomarker to DFS and superior to standard of care CEA.

Comparison of the NeuMoDx™ HBV quant assay and artus QS-RGQ® kit for HBV DNA quantitation in plasma samples

We aimed to compare the NeuMoDx HBV Assay with the artus HBV Assay using residual plasma samples and to evaluate the discordant results.The study included 200 patient samples analyzed with the NMD assay and stored at -80 °C. Samples were analyzed by artus in 2023. Discordant results were evaluated by cobas 6800 HBV DNA Test.Excellent agreement was found between both tests. Of the 100 samples that were HBV DNA negative by NMD, 93 were negative and 7 were positive by artus. With the Cobas test, 5 samples were positive. Of the100 HBV DNA positive samples detected by NMD, 99 were positive with the artus assay. This sample was also HBV DNA negative by the Cobas test. The sensitivity and specificity of NeuMoDx were found 93 % and 99 %, respectively.There was excellent qualitative agreement and strong quantitative correlation between the NeuMoDx and artus assays for HBV DNA detection and quantitation.

Bivalirudin Monitoring in Pediatric Ventricular Assist Device and Extracorporeal Membrane Oxygenation: Analysis of Single-Center Retrospective Cohort Data 2018-2022.

The activated partial thromboplastin time (aPTT) is the most frequently used monitoring assay for bivalirudin in children and young adults on mechanical circulatory support including ventricular assist devices (VADs) and extracorporeal membrane oxygenation (ECMO). However, intrinsic variability of the aPTT complicates management and risks bleeding or thrombotic complications. We evaluated the utility and reliability of a bivalirudin-calibrated dilute thrombin time (Bival dTT) assay for bivalirudin monitoring in this population. Retrospective analysis of clinical data (including aPTT, dilute thrombin time [dTT]) and results of residual plasma samples from VAD patients were assessed in two drug-calibrated experimental assays. One assay (Bival dTT) was validated for clinical use in VAD patients, and subsequently used by clinicians in ECMO patients. Pearson correlation and simple linear regression were used to determine R2 correlation coefficients between the different laboratory parameters using Statistical Package for Social Sciences (Armonk, NY). ICUs at Cincinnati Children's Hospital Medical Center. Children on VAD or ECMO support anticoagulated with bivalirudin. None. One hundred fifteen plasma samples from 11 VAD patients were analyzed. Both drug-calibrated experimental assays (anti-IIa and Bival dTT) showed excellent correlation with each other ( R2 = 0.94) and with the dTT ( R2 = 0.87), but poor correlation with aPTT ( R2 = 0.1). Bival dTT was selected for validation in VAD patients. Subsequently, clinically ordered results (105) from 11 ECMO patients demonstrated excellent correlation between the Bival dTT and the standard dTT ( R2 = 0.86) but very poor correlation with aPTT ( R2 = 0.004). APTT is unreliable and correlates poorly with bivalirudin's anticoagulant effect in ECMO and VAD patients. A drug-calibrated Bival dTT offers superior reliability and opportunity to standardize results across institutions. Additional studies are needed to determine an appropriate therapeutic range and correlation with clinical outcomes.

Capillary electrophoresis-mass spectrometry for creatinine analysis in residual clinical plasma samples and comparison with gold standard assay.

When hospitalized, infants, particularly preterm, are often subjected to multiple painful needle procedures to collect sufficient blood for metabolic screening or diagnostic purposes using standard clinical tests. For example, at least 100µL of whole blood is required to perform one creatinine plasma measurement with enzymatic colorimetric assays. As capillary electrophoresis-mass spectrometry (CE-MS) utilizing a sheathless porous tip interface only requires limited amounts of sample for in-depth metabolic profiling studies, the aim of this work was to assess the utility of this method for the determination of creatinine in low amounts of plasma using residual blood samples from adults and infants. By using a starting amount of 5µL of plasma and an injection volume of only 6.7nL, a detection limit (S/N=3) of 30nM could be obtained for creatinine, and intra- and interday precisions (for peak area ratios) were below 3.2%. To shorten the electrophoretic separation time, a multi-segment injection (MSI) strategy was employed to analyze up to seven samples in one electrophoretic run. The findings obtained by CE-MS for creatinine in pretreated plasma were compared with the values acquired by an enzymatic colorimetric assay typically used in clinical laboratories for this purpose. The comparison revealed that CE-MS could be used in a reliable way for the determination of creatinine in residual plasma samples from infants and adults. Nevertheless, to underscore the clinical efficacy of this method, a subsequent investigation employing an expanded pool of plasma samples is imperative. This will not only enhance the method's diagnostic utility but also contribute to minimizing both the amount and frequency of blood collection required for diagnostic purposes.

The lupus anticoagulant titer is associated with elevated antiphosphatidylserine/prothrombin immunoglobulin-M isotype antibody levels.

Clot based assays used for lupus anticoagulant (LAC) detection are typically interpreted in a qualitative fashion and may not reflect LAC potency. In this cross-sectional study, we describe a method for quantifying the LAC titer using serial (dependent) two-fold dilutions in normal pooled plasma. Serial dilutions of 51 residual plasma samples from 50 patients were tested using the Russell's viper venom screening time (DRVVT) and activated partial thromboplastin screening time (APTT) methodologies. The measured clotting times and the corresponding dilution factors were then used to derive a four-parameter logistic model. The LAC titer for each patient was interpolated as the sample dilution that corresponds to the upper reference interval limit of the corresponding assay. Calculated APTT and DRVVT LAC titers displayed a strong linear correlation (R2 = 0.84) between each other, but not with the degree of prolongation of the APTT/DRVVT screening time in the neat undiluted samples. Using data driven partitioning, patients could be grouped into low (<10) or high (≥10) DRVVT LAC titer. There were no significant differences in anticardiolipin (aCL) or anti-beta 2 glycoprotein 1 (aB2GPI) antibody levels or prevalence of thromboembolic events between low and high LAC titer groups. In contrast, antiphosphatidylserine/prothrombin (aPS/PT) IgM antibody levels, but not IgG, were significantly higher in the high LAC titer group. The degree of prolongation of the APTT/DRVVT screening time is not correlated with the LAC titer. Only aPS/PT IgM antibodies levels were strongly correlated with the LAC titers. Additional studies are warranted to determine clinical implications of high LAC titers.

Reference intervals for high sensitivity cardiac troponin I and N-terminal pro-B-type natriuretic peptide in children and adolescents on the Siemens Atellica.

The cardiac biomarkers high sensitivity cardiac troponin I (hs-cTnI) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) are utilised in paediatric healthcare for the diagnosis and prognostic assessment of many conditions including myocarditis, congenital heart disease, multisystem inflammatory syndrome in children (MIS-C) and heart failure. However, the standardised age-related reference intervals, 99th percentile cut-offs and clinical guidelines are not available, making the interpretation of these biomarkers challenging. This study aimed to generate normative data in a paediatric cohort for the Siemens Atellica® IM 1300 analyser. Residual plasma samples were collected from children aged up to 17 years attending primary care and out-patient settings and with no apparent evidence of cardiac dysfunction, renal dysfunction or other confounders. Reference intervals were generated using the 2.5th-97.5th percentiles, and 99th percentile cut-offs determined according to CLSI EP28-A3c. Statistical analysis revealed that partitioning was not required for gender for either biomarker. The reference interval for hs-cTnI for children aged one month to 16 years (n=292, 146 females and 146 males) was <14 ng/L with a 99th percentile cut-off of 19 ng/L. The reference interval for NT-proBNP for children aged one month up to one year was <714 ng/L (n=14) and for children aged 1-16 years (n=339) was <295 ng/L. This is the first paediatric reference interval data generated on the Siemens Atellica® solution. These reference intervals and 99th percentiles will inform clinical decisions in the paediatric cardiology setting.

Predicting recurrence using a tumor-uninformed ctDNA assay detecting MRD in patients with resected stage II or III colorectal cancer: Subset analysis from the GALAXY study in CIRCULATE-Japan.

21 Background: The presence of circulating tumor DNA (ctDNA) after curative-intent surgery can identify patients with minimal residual disease (MRD) who are at risk of recurrence and aid with postsurgical risk stratification. ~80% of stage II and only 50% of stage III colorectal cancer (CRC) patients are cured by surgery alone. A tumor-uninformed plasma-only approach for MRD assessment accelerates the turnaround time, enabling rapid adjuvant chemotherapy (ACT) treatment decision making, optimizing the impact on patient outcomes. Methods: A subset of samples from GALAXY, an observational arm of the CIRCULATE-Japan study (UMIN000039205), were analyzed for postsurgical ctDNA detection at a landmark time point (LMT) defined as 4 weeks after curative surgery in pathological stage II or III CRC patients. In a prospective lead-in to clinical validation, 80 patients meeting pre-specified eligibility criteria were randomly selected with enrichment for recurrence to 50% while maintaining the stage II:III recurrent (R)/nonrecurrent (NR) ratio to that observed in GALAXY. Residual plasma samples were analyzed with the Tempus xM assay (xM), a tumor-uninformed ctDNA MRD assay that integrates methylation and genomic variant MRD classifiers to deliver a binary MRD call. All calls were blinded to clinical outcomes. The methylation-based classifier detects fragments with CRC methylation signatures in differentially methylated regions trained by sequencing CRC and presumed-healthy samples on a 6Mbp panel. The variant-based MRD classifier detects highly prevalent CRC variants. Artifacts, CHIP, and germline variant filtering algorithms were also applied. Results: Of the 80 patients (pts), 70 [Stage II n= 29 (41%), Stage III n= 41 (59%)] were evaluable (36 R and 34 NR). At the LMT and with at least 1-year follow-up, 18/36 R pts had detectable ctDNA (xM MRD+) and 30/34 NR pts had undetectable ctDNA (xM MRD-), providing a sensitivity of 50% and specificity of 88%. Additionally, xM MRD+/- status strongly correlated with disease-free survival (DFS) with a hazard ratio (HR) of 5.09, adjusted to account for a 24% recurrence rate in GALAXY. In an updated, ongoing longitudinal analysis of the 4 false positive pts, 2 were Stage III, MRD+ from both the methylation and genomic classifiers, received ACT, and have likely cleared their ctDNA without any sign of clinical recurrence. An adjusted sensitivity and specificity analysis resulted in xM clinical performance of 53% (20/38 R) and 94% (30/32 NR), respectively. Conclusions: xM is a novel tumor-uninformed assay that demonstrated remarkable performance to detect clinical recurrence at a LMT, and a clinically meaningful correlation with DFS. A larger clinical validation study including longitudinal analysis, correlation with ACT, and outcomes from the GALAXY study is currently underway.

Evaluation of a New NT-proBNP Immunoassay on an Automated Core Laboratory System.

Heart failure remains a major cause of morbidity and mortality despite improvements in treatment. This study aimed to evaluate the Alere N-terminal pro B-type natriuretic peptide (NT-proBNP) immunoassay on the Abbott Alinity i platform. The analytical performance including precision, linearity, limit of quantitation (LOQ), carryover, dilution-recovery, and stability was evaluated. A method comparison between the Abbott Alere NT-proBNP assay and Roche Elecsys proBNP II assay was performed using 70 residual plasma samples. Total imprecision was 4.1%, 3.5%, and 2.3% for low (120.9 ng/L), medium (333.9 ng/L), and high (4767.4 ng/L) QC levels, respectively. The manufacturer's claimed LOQ of 8.3 ng/L was verified. Method comparison between the Alere NT-proBNP assay and the Elecsys proBNP II assay showed good agreement between assays with an R value of 0.998, a slope of 1.05 (95% CI, 1.03-1.06), and an intercept of 45.81 (95% CI, -46.6.84 to 138.22). The Bland-Altman plot showed an absolute bias of 250 ng/L or 6.02%. Subrange analysis (NT-proBNP <2000 ng/L) showed good agreement with an R value of 0.998, a slope of 1.04 (95% CI, 1.02-1.06), and an intercept of -4.83 (95% CI, -26.95 to 17.28), with a mean bias of 26 ng/L or 3.2%. The stability of NT-proBNP was also verified in lithium heparin plasma samples stored at 4°C over a 7-day period. Hemolysis and lipemia interference thresholds were verified, but icterus impacted NT-proBNP recovery by >20% at low analyte concentrations. The Alere NT-proBNP assay demonstrated acceptable analytical performance and very good clinical concordance with the Elecsys proBNP II assay.

Urine dipstick for screening plasma glucose and bilirubin in low resource settings: a proof-of-concept study.

The purpose of this proof-of-concept study was to investigate whether a commercially available urine dipstick may provide potentially useful information for screening plasma glucose and bilirubin in human plasma samples. Glucose and bilirubin were assayed in 60 anonymized lithium-heparin residual plasma samples using the Roche COBAS 8000 or after pipetting 10 µL of plasma onto the pads of a commercial urine dipstick. Semiquantitative urine test results obtained with the dipstick were directly compared to paired test results obtained with COBAS. Median plasma glucose values between COBAS and dipstick were slightly different (5.8 vs. 5.6 mmol/L; p=0.040), while no significant difference was found in bilirubin values between COBAS and dipstick (11.2 vs. 8.6 μmol/L; p=0.090). The Spearman's correlation between COBAS and dipstick was 0.83 (95% CI, 0.73-0.90; p<0.001) for plasma glucose and 0.78 (95% CI, 0.66-0.87; p<0.001) for plasma bilirubin, respectively. Cumulative agreement between COBAS and dipstick was high for both glucose (88%; kappa statistic statistics, 0.75; 95% CI, 0.58-0.92; p<0.001) and bilirubin (88%; kappa statistics, 0.76; 95% CI, 0.60-0.92; p<0.001). The results of this proof-of-concept study indicate that the commercial urine test strip used in our study provides acceptable performance for screening plasma glucose and bilirubin levels compared with reference laboratory assays.

Analysis of a German blood donor cohort reveals a high number of undetected SARS-CoV-2 infections and sex-specific differences in humoral immune response.

Seroprevalence studies can contribute to a better assessment of the actual incidence of infection. Since long-term data for Germany are lacking, we determined the seroprevalence of immunoglobulin G (IgG) antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in residual plasma samples of 3,759 German regular blood donors between July 2020 and June 2021. Over almost the entire study period, the incidences determined based on our data were higher than those officially reported by the Robert Koch Institute, the public health institute in Germany. Using our serological testing strategy, we retrospectively detected natural infection in 206/3,759 (5.48%; 95% confidence interval (CI): 4.77-6.25) individuals. The IgG seroprevalence ranked from 5.15% (95% CI: 3.73-6.89) in Lower Saxony to 5.62% (95% CI: 4.57-6.84) in North Rhine Westphalia. The analyses of follow-up samples of 88 seropositive blood donors revealed a comparable fast decay of binding and neutralizing anti-SARS-CoV-2 IgG antibodies. The antibody avidity remained at a low level throughout the whole follow-up period of up to 181 days. Interestingly, female donors seem to express a stronger and longer lasting humoral immunity against the new coronavirus when compared to males. Conclusion: Overall, our data emphasizes that seroprevalence measurements can and should be used to understand the true incidence of infection better. Further characterization of follow-up samples from seropositive donors indicated rapid antibody waning with sex-specific differences concerning the strength and persistence of humoral immune response.

Total bilirubin assay differences may cause inconsistent treatment decisions in neonatal hyperbilirubinaemia.

To assess interlaboratory variability of total serum bilirubin (TSB) results in newborns. Initiated following a clinical incident in which a neonate was transferred to a tertiary hospital for treatment of severe hyperbilirubinemia but on arrival was reclassified into alower risk category due to a 20% difference in TSB between laboratories. Fresh residual plasma samples from hospital-born infants were pooled to obtain 11 samples across a range of total bilirubin concentrations. Aliquots were light-protected and measured on 7 commercial platforms at 4accredited medical laboratories. Data from The Royal College of Pathologists of Australasia Quality Assurance Programs' (RCPAQAP) Neonatal Bilirubin program was analysed. Twenty-four to 30% difference in results for individual samples, largely due to calibration differences between assays. When interpreted according to guidelines,results from different platforms would have ledto different clinical interventions in some cases. RCPAQAP results showed significant within-method bias but were not shown to be commutable with patient samples. There are clinically significant method-dependent differences in TSB results from neonatal samples, consistent with our clinical incident. The differences are largely due to lack of standardisation of calibrator values. Thishas implications for healthcare resource use and possiblyfor the neurodevelopment of infants. Intervention isneeded ata number of levels, including clinical reporting ofincidents arising from discordant results, commitment by manufacturers to ensure metrological traceability of methods with sufficiently low uncertainty in the final measurements, andavailability of commutable quality assurance material to monitor assay performance, especially at the clinical decision points for neonatal jaundice.

Use of Bivalirudin-Specific Monitoring Assays in Ventricular Assist Device Patients

Increasing numbers of pediatric ventricular assist device (VAD) patients are being anticoagulated with the parenteral direct thrombin inhibitor bivalirudin because it is reportedly associated with fewer bleeding and thrombotic events. With expanded use, management is shifting from a handful of experts to a wider pool of clinicians and trainees, increasing the importance of identifying broadly acceptable, standardized monitoring assays. The pharmacokinetics of bivalirudin have not been well-studied in the pediatric population and drug monitoring in all ages has been problematic for critically ill patients who require intermediate or longer-term therapeutic anticoagulation. The dilute thrombin time (dTT), available in many clinical laboratories, has been suggested as a potentially superior alternative to the activated partial thromboplastin time (aPTT), but results have been inconsistent. As clinical use of the dTT (c-dTT) for monitoring bivalirudin increased at our institution, we sought to evaluate the performance of commercially available, “research only” functional bivalirudin assays with calibrators and controls to measure bivalirudin's anticoagulation effect, utilizing residual plasmas and clinical data from VAD patients treated with bivalirudin. Residual citrated, platelet poor plasma samples from clinically ordered laboratory tests in VAD patients were collected and stored frozen at -70 oC from February 8, 2018, to January 4, 2021. With IRB approval, the samples were analyzed in conjunction with medical record review. Two experimental assay kits were utilized, ex-dTT: a dilute thrombin time assay (Hemoclot, Hyphen-Biomed, FR) and ex-anti FIIa: a chromogenic anti-factor IIa assay (BiophenDTI, Hyphen-Biomed, FR). Bivalirudin calibrators (Biophen, Hyphen-Biomed, FR) were used to develop a standard curve for the assays. Controls of low and high (1.5 and 4 microgram/mL) bivalirudin (Biophen, Hyphen-Biomed, FR) were used for quality control of the assays. Results from the two experimental assays were compared with available standard laboratory monitoring when results were available. In total, 115 residual plasma samples from 11 different patients (up to 16 samples per patient) were analyzed. Subjects included 1 adult (37 yr.) and 10 pediatric patients (0-18 yr.). There was excellent correlation between the two experimental assays (Fig. 1A). Correlation was good between the c-dTT and each of the experimental assays; however, with a clinical laboratory platform change (instrument, reagents) midway through sample collection, the c-dTT results shifted substantially in their corresponding estimate of bivalirudin concentration (Figs 1B and C). Activated partial thromboplastin time (aPTT) had poor correlation with the c-dTT and with each of the experimental assays (Fig. 1D). Here we report results from two commercially available kits that estimate bivalirudin concentration using dTT or chromogenic anti-factor IIa assays, in comparison with clinically generated results from VAD patients treated with bivalirudin. Our findings agree with previous observations that the aPTT shows poor correlation with dTT assays (clinically used and experimental) over days and weeks of anticoagulation. The two experimental assays had excellent correlation with each other and good correlation with the c-dTT; however, the fact that the c-dTT results shifted dramatically with a clinical laboratory platform change is illustrative of the need for a bivalirudin-specific monitoring assay as an essential tool for improving outcomes at our center and across centers. More research is needed to understand which type of monitoring assay (dTT or anti-FIIa) may be better suited to particular clinical circumstances. [Display omitted] DisclosuresLorts: Abbott: Consultancy; Medtronic: Consultancy; Berlin Heart: Consultancy; Syncardia: Consultancy; Abiomed: Consultancy.

Trends in SARS-CoV-2 seroprevalence amongst urban paediatric patients compared with a nationwide cohort in the Netherlands

ObjectivesThe extent of SARS-CoV-2 infection amongst children and their role in transmission remains unclear. Therefore, we aimed to estimate the SARS-CoV-2 antibody seroprevalence amongst children who presented to our hospital for non-COVID-19-related morbidity during the first and second epidemic wave in 2020 and compared these to the general Dutch paediatric population. MethodsWe collected residual plasma samples from all paediatric patients (1 month-17 years of age) visiting our clinic or emergency room, who had blood drawing for various medical reasons. Samples were analysed for the presence of total antibodies against SARS-CoV-2 by Wantai ELISA. The seroprevalence in two separate periods (July-Sep 2020, and Oct-Dec 2020) was compared to regional and national data (PIENTER-Corona study, September 2020), and associations with co-morbidities were assessed. ResultsA total of 209 samples in period 1 and 240 samples in period 2 were collected (median age 7.1 years, IQR 1.5–13.5). SARS-CoV-2 antibodies were detected in 4.1% and 13.8%, respectively (p< 0.001). Seroprevalence was higher compared to national paediatric data, but did not differ with regional estimates. Most children with SARS-CoV-2 antibodies were seen in the outpatient clinic for general paediatric problems with no differences in medical reasons for presentation between the two periods. ConclusionsThese data confirm a rapid three-fold increase in SARS-CoV-2 seroprevalence in paediatric patients in the second half of 2020 with a trend towards a higher seroprevalence compared to randomly-selected children in a nationwide study. Underlying morbidity in children might not play an important role in acquiring SARS-CoV-2 infection.

Sex steroid hormones are associated with mortality in COVID-19 patients: Level of sex hormones in severe COVID-19.

In patients with coronavirus disease 2019 (COVID-19), men are more severely affected than women. Multiple studies suggest that androgens might play a role in this difference in disease severity. Our objective was to assess the association between sex hormone levels and mortality in patients with severe COVID-19.We selected patients from the Amsterdam University Medical Centers COVID-19 Biobank, in which patients admitted to hospital in March and April 2020, with reverse transcription-polymerase chain reaction proven severe acute respiratory syndrome-coronavirus-2 infection, were prospectively included. Specifically, we included postmenopausal women (>55 years) and age-matched men, with a mortality of 50% in each group. Residual plasma samples were used to measure testosterone, estradiol, sex hormone binding globulin (SHBG), and albumin. We investigated the association of the levels of these hormones with mortality in men and women.We included 16 women and 24 men in March and April 2020 of whom 7 (44%) and 13 (54%), respectively, died. Median age was 69 years (interquartile range [IQR] 64–75). In men, both total and free testosterone was significantly lower in deceased patients (median testosterone 0.8 nmol/L [IQR 0.4–1.9] in deceased patients vs 3.2 nmol/L [IQR 2.1–7.5] in survivors; P < .001, and median free testosterone 33.2 pmol/L [IQR 15.3–52.2] in deceased patients vs 90.3 pmol/L [IQR 49.1–209.7] in survivors; P = .002). SHBG levels were significantly lower in both men and women who died (18.5 nmol/L [IQR 11.3–24.3] in deceased patients vs 34.0 nmol/L [IQR 25.0–48.0] in survivors; P < .001). No difference in estradiol levels was found between deceased and surviving patients.Low SHBG levels were associated with mortality rate in patients with COVID-19, and low total and free testosterone levels were associated with mortality in men. The role of testosterone and SHBG and potential of hormone replacement therapy needs further exploration in COVID-19.

Seroprevalence of Anti-SARS-CoV-2 Antibodies in Blood Donors from Nuevo Leon State, Mexico, during 2020: A Retrospective Cross-Sectional Evaluation.

The progression and distribution of the SARS-CoV-2 pandemic are continuously changing over time and can be traced by blood donors’ serological survey. Here, we investigated the seroprevalence of anti-SARS-CoV-2 antibodies in blood donors in Nuevo Leon, Mexico during 2020 as a strategy for the rapid evaluation of the spread of SARS-CoV-2 and asymptomatic case detection. We collected residual plasma samples from blood donors who attended two regional donation centers from January to December of 2020 to identify changes in anti-SARS-CoV-2 IgG prevalence. Plasma samples were analyzed on the Abbott Architect instrument using the commercial Abbott SARS-CoV-2 IgG chemiluminescent assay. We found a total of 99 reactive samples from 2068 analyzed plasma samples, resulting in a raw prevalence of 4.87%. Donors aged 18–49 years were more likely to be seropositive compared to those aged >50 years (p < 0.001). Weekly seroprevalence increased from 1.8% during the early pandemic stage to 27.59% by the end of the year. Prevalence was 1.46-fold higher in females compared to males. Case geographical mapping showed that Monterrey city recorded the majority of SARS-CoV-2 cases. These results show that there is a growing trend of seroprevalence over time associated with asymptomatic infection that is unnoticed under the current epidemiological surveillance protocols.

HIV-1 Subtype C Drug Resistance Mutations in Heavily Treated Patients Failing Integrase Strand Transfer Inhibitor-Based Regimens in Botswana.

There are limited real-world mutational and virological outcomes data of treatment-experienced persons diagnosed with HIV-1 subtype C (HIV-1 C) who are failing Integrase Strand Transfer Inhibitor-based regimens. Requisition forms sent for HIV-1 genotypic resistance testing (GRT) between May 2015 and September 2019 were reviewed and participants experiencing virologic failure while on dolutegravir (DTG) or raltegravir (RAL) cART at sampling recruited. Sanger sequencing of the HIV-1 Pol gene was performed from residual plasma samples and drug resistance mutational (DRM) analysis performed using the Stanford University HIV drug resistance database. 40 HIV-1C integrase sequences were generated from 34 individuals, 24 of whom were on DTG cART, three on RAL cART and seven on an unknown (DTG or RAL)-anchored cART at time of GRT. 11/34 (32%) individuals had DRMs to DTG and other integrase inhibitors. 7/11 (64%) patients had exposure to a RAL-based cART at the time of sampling. Out of the 11 individuals with DRMs, one (9%) had 2-class, 6 (55%) had 3-class, and 4 (36%) had 4-class multidrug-resistant HIV-1C. 7/11 individuals (64%) are currently virologically suppressed. Of the four individuals not virologically suppressed, three had extensive DRMs involving 4-classes of ARV drugs and one individual has demised. Resistance to DTG occurs more often in patients exposed to RAL cART. Individuals with 4-class DRMs plus integrase T97 and E157Q mutations appear to have worse outcomes. There is a need for frequent VL monitoring and GRT amongst treatment-experienced HIV-1C diagnosed individuals.

Epidemiological factors associated with recent HIV infection among newly-diagnosed cases in Singapore, 2013\u20132017

BackgroundEarly diagnosis is crucial in securing optimal outcomes in the HIV care cascade. Recent HIV infection (RHI) serves as an indicator of early detection in the course of HIV infection. Surveillance of RHI is important in uncovering at-risk groups in which HIV transmission is ongoing. The study objectives are to estimate the proportion of RHI among persons newly-diagnosed in 2013–2017, and to elucidate epidemiological factors associated with RHI in Singapore.MethodsAs part of the National HIV Molecular Surveillance Programme, residual plasma samples of treatment-naïve HIV-1 positive individuals were tested using the biotinylated peptide-capture enzyme immunoassay with a cutoff of normalized optical density ≤ 0.8 for evidence of RHI. A recent infection testing algorithm was applied for the classification of RHI. We identified risk factors associated with RHI using logistic regression analyses.ResultsA total of 701 newly-diagnosed HIV-infected persons were included in the study. The median age at HIV diagnosis was 38 years (interquartile range, 28–51). The majority were men (94.2%), and sexual route was the predominant mode of HIV transmission (98.3%). Overall, 133/701 (19.0, 95% confidence interval [CI] 16.2–22.0%) were classified as RHI. The proportions of RHI in 2015 (31.1%) and 2017 (31.0%) were significantly higher than in 2014 (11.2%). A significantly higher proportion of men having sex with men (23.4, 95% CI 19.6–27.6%) had RHI compared with heterosexual men (11.1, 95% CI 7.6–15.9%). Independent factors associated with RHI were: age 15–24 years (adjusted odds ratio [aOR] 4.18, 95% CI 1.69–10.31) compared with ≥55 years; HIV diagnosis in 2015 (aOR 2.36, 95% CI 1.25–4.46) and 2017 (aOR 2.52, 95% CI 1.32–4.80) compared with 2013–2014; detection via voluntary testing (aOR 1.91, 95% CI 1.07–3.43) compared with medical care; and self-reported history of HIV test(s) prior to diagnosis (aOR 1.72, 95% CI 1.06–2.81).ConclusionAlthough there appears to be an increasing trend towards early diagnosis, persons with RHI remain a minority in Singapore. The strong associations observed between modifiable behaviors (voluntary testing and HIV testing history) and RHI highlight the importance of increasing the accessibility to HIV testing for at-risk groups.

Evaluation of Imatinib Concentrations in Samples Submitted for BCR-ABL1 or Imatinib Testing-Evidence to Support Therapeutic Drug Monitoring for Dose Optimization?

Imatinib is one of the first-line therapies for chronic myeloid leukemia. Achieving a major molecular response early in treatment, as indicated by a BCR-ABL1 major international scale result of ≤0.1% within 6 months, is associated with better patient outcomes and is statistically associated with a trough imatinib concentration of approximately 1000 ng/mL. Adherence to therapy, drug resistance, drug-drug interactions, and pharmacokinetic/pharmacodynamic factors may hinder attaining this target. Therapeutic drug monitoring of imatinib is not currently standard-of-care, but may help to evaluate adherence and optimize treatment of patients with chronic myeloid leukemia. This study aimed to evaluate imatinib concentrations in real-world patient plasma samples to identify the proportion of imatinib-treated patients who achieved the therapeutic target of 1000 ng/mL. This was a retrospective, observational study that measured imatinib in residual plasma samples used for BCR-ABL1 tests (n = 1022) and analyzed clinician-ordered imatinib tests for therapeutic drug monitoring (n = 116). Imatinib was measured by competitive immunoassay. The frequency of imatinib concentrations achieving the therapeutic target was determined and correlated with BCR-ABL1 major international scale, age, and sex. Seventy-two percent of patients tested for BCR-ABL1 may not have been prescribed or were not adherent to imatinib therapy. In the 29% of patients who did not achieve major molecular response, but had quantifiable imatinib concentrations, the therapeutic concentration was not met. For clinician-ordered imatinib tests, 45% of samples did not exceed the therapeutic target and 4% had potentially toxic plasma concentrations (>3000 ng/mL). Therapeutic drug monitoring for imatinib may assist clinicians in the identification of patients who may not be adherent to therapy, display variable pharmacokinetics or pharmacodynamics, or may be experiencing toxicity or treatment failure.

Comparison of Low Molecular Weight Heparin Activity Assays with and without Addition of Exogenous Antithrombin in a Pediatric and Young Adult Leukemia Cohort

Introduction: Enoxaparin (low molecular weight heparin, LMWH) is the most commonly prescribed anticoagulant for pediatric patients with venous thromboembolism (VTE) (Goldenberg et al. 2015). The gold-standard LMWH activity (anti-Xa activity) assays differ in whether they add exogenous antithrombin (AT) or dextran sulfate (Ignjatovic et al. 2007). Adding AT would "standardize" results in patients with low antithrombin, such as infants and asparaginase-treated patients (Mitchell et al 2010); however, questions remain about which assay best reflects the patient's anticoagulation effect and the degree of discrepancy between assays. We assessed LMWH activity in residual plasma samples from a cohort of anticoagulated pediatric acute lymphoblastic leukemia and lymphoma (ALL) patients, with history of VTE and variable AT levels, on four platforms (two instruments and their kits +/- exogenous AT). Methods: We analyzed 60 de-identified residual plasma samples from 12 anticoagulated ALL patients (2-19 years. Mean 13.75 yr) who had AT levels obtained for clinical care. All consented to the IRB-approved Oncology Tissue Repository. LMWH activity was assessed on Siemens and Stago instruments using their recommended kits that did or did not contain exogenous AT (Table 1), according to manufacturer recommendations, by experienced laboratorians. Results: Results were interpretable on 236/240 with 4 rejected for lipemia. Mean AT activity was 80 (42-138 ng/ml, lab normal &gt;81%). Correlation was acceptable for the published kit ranges of LMWH activity when comparing kits +AT (Berichrom® to Stachrom®, r=0.82, p&lt;0.0001), -AT (Innovance® to STA®-Liquid Anti-Xa: r=0.93, p&lt;0.0001), and within the same manufacturer (Berichrom® to Innovance®, r=0.92, p&lt;0.0001, Stachrom® to STA®-Liquid Anti-Xa r=0.98, p&lt;0.0001) (Table 2, Figure 1, Figure 2). Comparing +AT or not by manufacturer, there was a nonsignificant trend to higher LMWH activity result with +AT kits. When AT levels were &lt;70 ng/ml (n=19, mean 56 ng/dl) there was a trend to underestimate LMWH activity when AT was not added; this reached significance when the Stago methods were compared (Table 2.) Conclusions: There is acceptable correlation of LMWH activity using kits with or without exogenous AT in anticoagulated pediatric plasma samples; however, in low AT samples, LMWH activity trends lower in platforms without exogenous AT. Use of residual samples precluded conclusions about the clinical impact of this difference; however, there were a few instances where subtherapeutic activity in the -AT assay was in the therapeutic range (0.5-1 activity units) in the +AT assay. Clinicians should know whether exogenous AT is used in their own laboratory's assay and understand that added AT could overestimate the LMWH effect in patients with low AT levels. Disclosures Schaefer: Stago: Research Funding; Siemens: Research Funding.

156. Direct Detection and Quantification of Bacterial Cell-free DNA in Patients with Infective Endocarditis (IE) Using the Karius Plasma Next Generation Sequencing (NGS) Test

BackgroundThe variable clinical presentation of IE requires a diagnostic tool that accurately detects a wide range of organisms, including in culture-negative (CN) scenarios. A sensitive molecular diagnostic assay that quantitates pathogen DNA could be a useful tool to diagnose IE and evaluate response to antimicrobial therapy.MethodsWe prospectively enrolled 30 hospitalized adult patients evaluated for acute IE classified using the Duke Criteria. Residual plasma samples within 24 hours and/or fresh whole blood within 48–72 hours of enrollment blood culture were collected. Additional samples were collected every 2–3 days for up to 7 time points until discharge. Samples were shipped to the Karius laboratory (Redwood City, California) for testing. Cell-free DNA was extracted and NGS was performed. Human sequences were removed and remaining sequences were aligned to a curated pathogen database of over 1,000 organisms. Organisms present above a predefined statistical threshold were reported. Quantity of DNA for each reported pathogen was expressed as molecules per microliter.ResultsOf 29 patients eligible for analysis, 18 had prosthetic valves and 7 had implanted cardiac devices. Twenty-four patients had Definite IE. Twenty patients had positive blood cultures (including S. aureus, S. epidermidis, E. faecalis, S. agalactiae, Pantoea ananatis, S. sanguinis, C. albicans); NGS identified the same organism isolated in all 20 patients as well as E. cloacae complex, and E. faecalis in 2 of 4 CN Definite IE patients. For 1 CN patient with Possible IE, NGS identified E. coli. NGS and BC were negative for 4 patients with Rejected IE. NGS identified the IE etiology in patients pretreated with antibiotics up to 20 days prior to sample collection. Pathogen DNA signal was often observed in both initial and repeat plasma samples, while repeat blood cultures remained negative.ConclusionThis novel, cell-free pathogen quantitative NGS plasma assay accurately identified causative organisms in patients with IE, even when blood cultures were negative due to pretreatment with antibiotics. Pathogen DNA, detected in plasma longer than blood culture, is a promising biomarker to aid in the diagnosis and monitoring of IE, particularly culture-negative IE.Disclosures P. Shah, Karius Inc.: Collaborator and Research Contractor, Salary. F. Ruffin, Karius Inc.: Collaborator and Research Contractor, Salary. H. Seng, Karius Inc.: Employee, Salary. D. Hollemon, Karius Inc.: Employee, Salary. L. Winn, Karius Inc.: Collaborator and Research Contractor, Salary. C. Drennan, Karius Inc.: Collaborator and Research Contractor, Salary. K. L. Chan, Karius Inc.: Employee, Salary. H. Quach, Karius Inc.: Employee, Salary. T. Blauwkamp, Karius Inc.: Employee, Salary. G. Meshulam-Simon, Karius Inc.: Employee, Salary. D. Hong, Karius Inc.: Employee, Salary. V. G. Fowler Jr., Merck, Cerexa/Actavis, Pfizer, Advanced Liquid Logis, NIH, MedImmune, Basilea, Karius, Contrafect, Regneron, Genentech, Affinergy, Locus, Medical Surface, Inc., Achaogen, Astellas, Arsanis, Bayer, Cubist, Debiopharm, Durata, Grifols, Medicines Co, Novartis: Collaborator, Consultant and Scientific Advisor, Consulting fee, Research grant and Research support.