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Background: PCSK9 (proprotein convertase subtilisin-kexin type 9) chaperones the hepatic LDLR (low-density lipoprotein receptor) for lysosomal degradation, elevating serum LDL (low-density lipoprotein) cholesterol and promoting atherosclerotic heart disease. Though the major effect on the hepatic LDLR comes from secreted PCSK9, the details of PCSK9 reuptake into the hepatocyte remain unclear. In both tissue culture and animal models, HSPGs (heparan sulfate proteoglycans) on hepatocytes act as co-receptors to promote PCSK9 reuptake. We hypothesized that if this PCSK9:HSPG interaction is important in humans, disrupting it with unfractionated heparin (UFH) would acutely displace PCSK9 from the liver and increase plasma PCSK9. Methods: We obtained remnant plasma samples from 160 subjects undergoing cardiac catheterization before and after administration of intravenous UFH. PCSK9 levels were determined using a commercial enzyme-linked immunosorbent assay. Results: Median plasma PCSK9 was 113 ng/mL prior to UFH and 119 ng/mL afterward. This difference was not significant ( P =0.83 [95% CI, −6.23 to 6.31 ng/mL]). Equivalence testing provided 95% confidence that UFH would not raise plasma PCSK9 by > 4.7%. Among all subgroups, only subjects with the lowest baseline PCSK9 concentrations exhibited a response to UFH (8.8% increase, adj. P =0.044). A modest correlation was observed between baseline plasma PCSK9 and the change in plasma PCSK9 due to UFH (R S =−0.3634; P Conclusions: Administration of UFH does not result in a clinically meaningful effect on circulating PCSK9 among an unselected population of humans. The results cast doubt on the clinical utility of disrupting the PCSK9:HSPG interaction as a general therapeutic strategy for PCSK9 inhibition. However, the observations suggest that in selected populations, disrupting the PCSK9:HSPG interaction could still affect PCSK9 reuptake and offer a therapeutic benefit.

Background Biomarkers have been widely explored for coronavirus disease 2019 diagnosis. Both viral RNA or antigens (Ag) in the respiratory system and antibodies (Ab) in blood are used to identify active infection, transmission risk, and immune response but have limitations. This study investigated the diagnostic utility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein (N-Ag) in serum. Methods We retrospectively studied 208 randomly selected cases with SARS-CoV-2 infection confirmed by viral RNA test in swabs. N-Ag concentrations were measured in remnant serum samples, compared to viral RNA or Ab results, and correlated to electronic health records for clinical value evaluation. Results Serum N-Ag was detected during active infection as early as day 2 from symptom onset with a diagnostic sensitivity of 81.5%. Within 1 week of symptom onset, the diagnostic sensitivity and specificity reached 90.9% (95% CI, 85.1%–94.6%) and 98.3% (95% CI, 91.1%–99.9%), respectively. Moreover, serum N-Ag concentration closely correlated to disease severity, reflected by highest level of care, medical interventions, chest imaging, and the length of hospital stays. Longitudinal analysis revealed the simultaneous increase of Abs and decline of N-Ag. Conclusions Serum N-Ag is a biomarker for SARS-CoV-2 acute infection with high diagnostic sensitivity and specificity compared to viral RNA in the respiratory system. There is a correlation between serum N-Ag concentrations and disease severity and an inverse relationship of N-Ag and Abs. The diagnostic value of serum N-Ag, as well as technical and practical advantages it could offer, may meet unsatisfied diagnostic and prognostic needs during the pandemic.

Objective Irinotecan (CPT-11) is an important drug used in the treatment of several solid tumor types. To minimize its toxicity, therapeutic drug monitoring of CPT-11 and its major metabolites (SN-38, SN-38-glucuronide [SN-38G], and APC) has been proposed. We aimed to develop a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of CPT-11 and its major metabolites in plasma. Methods Specimen preparation consisted of protein precipitation, evaporation, and reconstitution. Analyses were performed on a C18 column using reverse-phase gradient elution. Electrospray ionization and multiple reaction monitoring in positive mode were used for MS. The following heavy isotope–labeled internal standards were used: CPT-11 D10, SN-38 D3, SN-38G D3, and APC D3. Results We found that CPT-11, SN-38G, and APC eluted at ~4.6 to 4.7 minutes, and SN-38 eluted at ~5.1 to 5.2 minutes. A second peak for SN-38 was detected at ~4.6 to 4.7 minutes. Given that the structure of SN-38 is found in CPT-11, SN-38G, and APC, and in the CPT-11 D10 used here, in-source fragmentation was the likely cause. In addition, we found that a low-level SN-38 impurity was present in CPT-11 D10 and to a lesser extent in SN-38 D3. Conclusion When developing methods for CPT-11 and its metabolites, it is important to consider the effects of in-source fragmentation and the choice of internal standards.

Serosurveillance provides a unique opportunity to quantify the proportion of the population that has been exposed to pathogens. Here, we developed and piloted Serosurveillance for Continuous, ActionabLe Epidemiologic Intelligence of Transmission (SCALE-IT), a platform through which we systematically tested remnant samples from routine blood draws in two major hospital networks in San Francisco for SARS-CoV-2 antibodies during the early months of the pandemic. Importantly, SCALE-IT allows for algorithmic sample selection and rich data on covariates by leveraging electronic health record data. We estimated overall seroprevalence at 4.2%, corresponding to a case ascertainment rate of only 4.9%, and identified important heterogeneities by neighborhood, homelessness status, and race/ethnicity. Neighborhood seroprevalence estimates from SCALE-IT were comparable to local community-based surveys, while providing results encompassing the entire city that have been previously unavailable. Leveraging this hybrid serosurveillance approach has strong potential for application beyond this local context and for diseases other than SARS-CoV-2., Population-based surveys are the gold standard for estimating seroprevalence but are expensive and often only capture a small geographic area or window of time. This study describes a new platform, SCALE-IT, for serosurveillance based on algorithmic sampling of electronic health records, and uses it to estimate the seroprevalence of SARS-CoV-2 in San Francisco.

Many natural products have biological effects on humans and animals. Poisoning caused by natural products is common in clinical toxicology cases. Liquid chromatography–high-resolution mass spectrometry (LC–HRMS) has recently emerged as a powerful analytical tool for large-scale target screening, and the application of LC–HRMS can be expanded to evaluate potential natural product poisoning in clinical cases. We report the construction of an LC–HRMS spectral library of 95 natural products commonly implicated in poisoning, and an LC–HRMS assay was validated for definitive detection of natural products in urine and serum samples. For each compound, the limit of detection was determined in the analytical range of 1.0–1,000 ng/mL for urine samples and 0.50–500 ng/mL for serum samples. The mean (SD) values of matrix effects for urine samples and that for serum samples were both −21% (22%), and the mean (SD) value of recovery for serum samples was 89% (26%). The LC–HRMS assay was successfully applied to identify natural products in clinical cases. The spectral library parameters of each compound are provided in the supplementary material to aid other laboratories in identification of unknown natural toxins and development of similar methods on different mass spectrometry platforms.

Race and Genetic Ancestry in Medicine U.S. health inequities won’t be eliminated by abandoning the use of race and ethnicity in research and clinical practice, since these variables capture key epi...

Background Concerns exist regarding how the 99th percentile upper reference limit (URL) of cardiac troponin (cTn) is determined and whether it should be derived from normal healthy individuals. Content The 99th percentile URL of cTn is an important criterion to standardize the diagnosis of myocardial infarction (MI) for clinical, research, and regulatory purposes. Statistical heterogeneity in its calculation exists but recommendations have been proposed. Some negativity has resulted from the fact that with some high-sensitivity (hs) cTn assays, a greater number of increases above the 99th percentile are observed when transitioning from a contemporary assay. Increases reflect acute or chronic myocardial injury and provide valuable diagnostic and prognostic information. The etiology of increases can sometimes be difficult to determine, making a specific treatment approach challenging. For those reasons, some advocate higher cutoff concentrations. This approach can contribute to missed diagnoses. Contrary to claims, neither clinical or laboratory guidelines have shifted away from the 99th percentile. To support the diagnosis of acute MI, the 99th percentile URL remains the best-established approach given the absence of cTn assay standardization. Importantly, risk stratification algorithms using hs-cTn assays predict the possibility of MI diagnoses established using the 99th percentile. Summary The 99th percentile of cTn remains the best-established criterion for the diagnosis of acute MI. While not perfect, it is analytically and clinically evidence-based. Until there are robust data to suggest some other approach, staying with the 99th percentile, a threshold that has served the field well for the past 20 years, appears prudent.

Background Daratumumab (DARA) is a fully human anti-CD38 IgG1-κ monoclonal antibody drug used in the treatment of multiple myeloma (MM). While serum protein electrophoresis (SPEP) is an important assay for diagnosis and monitoring of patients with MM, DARA can appear in the γ-region as a single band and interfere with the interpretation of SPEP results. An approach to detect the interference is measuring the quantity of DARA in serum samples and assessing its impact on SPEP results. Immunoassays based on label-free technologies, i.e. label-free immunoassays (LFIA’s), can achieve real-time immunometric measurement without attaching a reporter molecule (enzyme, fluorophore, etc.) to the immunocomplex. The recorded time course of the immunocomplex formation allows for quantitation on initial binding rate, which facilitates rapid measurement within a few minutes. Based on the thin-film interferometry (TFI) technology, a rapid LFIA was established for the quantitation of DARA in serum samples. Methods The TFI-based LFIA for DARA was validated for imprecision (CV), accuracy, limit of quantitation (LOQ), and analytical measurement range (AMR). Interference to the LFIA was evaluated using a group of protein samples, as well as hemolytic, lipemic, and icteric clinical samples. Results The precision of the TFI-based LFIA’s for DARA ranged from 6.5% to 10.7% (within-run CV), and 7.4% to 11.6% (between-run CV), with a bias of −2.1% to 10.1%. The LOQ was 10 μg/ml (n = 4, CV 9.8%), with an AMR ranging from the LOQ to 1000 μg/ml. The LFIA was used to measure 37 patient samples submitted for SPEP testing. The LFIA results were 100% consistent with the history of DARA use as documented in the medical record. Conclusions The TFI-based LFIA was successful at accurately identifying DARA in serum samples and can be used to identify DARA interference in SPEP testing. This work demonstrates the applicability of label-free technologies, particularly the TFI technology, to clinical diagnostic needs. Given the simplicity and the speed of the testing process, the TFI technology provides a unique testing approach for the measurement of proteins in clinical samples.

Background Some therapeutic drugs are unstable during sample storage in gel tubes. BD Vacutainer® Barricor™ Plasma Blood Collection Tube with nongel separator was compared with plasma gel tubes, BD Vacutainer PST™, PST II, and BD Vacutainer Serum Tube for acetaminophen, salicylate, digoxin, carbamazepine, phenytoin, valproic acid, and vancomycin during sample storage for up to 7 days. Methods Seven hospital sites enrolled 705 participants who were taking at least one selected drug. The study tubes were collected and tested at initial time (0 h), after 48 h of storage at room temperature and on day 7 (after additional 5 days of refrigerated storage). The performance of BD Barricor tube was evaluated for each drug by comparing BD Barricor samples with samples from the other tubes at 0 h from the same participant; stability was evaluated by comparing test results from the same tube at 0 h, 48 h, and 7 days. Results At 0 h, BD Barricor showed clinically equivalent results for selected therapeutic drugs compared with the other tubes, except phenytoin in BD PST. Phenytoin samples ≥20 µg/mL in BD PST had 10–12% lower values than samples in BD Barricor. During sample storage, all selected drugs remained stable for 7 days in BD Barricor and in serum aliquots. In BD PST, all drugs remained stable except phenytoin and carbamazepine and in BD PST II except for phenytoin. Conclusion The BD Barricor Tube is effective for the collection and storage of plasma blood samples for therapeutic drug monitoring without sample aliquoting.

Background How to select healthy reference subjects in deriving 99th percentiles for cardiac troponin assays still needs to be clarified. To assist with global implementation of high sensitivity (hs)-cardiac troponin (cTn) I and hs-cTnT assays in clinical practice, we determined overall and sex-specific 99th percentiles in 9 hs-cTnI and 3 hs-cTnT assays using a universal sample bank (USB). Methods The Universal Sample Bank (USB) comprised healthy subjects, 426 men and 417 women, screened using a health questionnaire. Hemoglobin A1c (>URL 6.5%), NT-proBNP (>URL 125 ng/L) and eGFR ( Results Subjects were ages 19 to 91 years, Caucasian 58%, African American 27%, Pacific Islander/Asian 11%, other 4%, Hispanic 8%, and non-Hispanic 92%. The overall and sex-specific 99th percentiles for all assays, before and after exclusions (n = 694), were influenced by the statistical method used, with substantial differences noted between and within both hs-cTnI and hs-cTnT assays. Men had higher 99th percentiles (ng/L) than women. The Roche cTnT and Beckman and Abbott cTnI assays (after exclusions) did not measure cTn values at ≥ the limit of detection in ≥50% women. Conclusions Our findings have important clinical implications in that sex-specific 99th percentiles varied according to the statistical method and hs-cTn assay used, not all assays provided a high enough percentage of measurable concentrations in women to qualify as a hs-assay, and the surrogate exclusion criteria used to define normality tended to lower the 99th percentiles.

Cardiovascular disease (CVD) and heart failure (HF) are disproportionately high in people living with HIV and differ by sex. Few CVD-related studies focus on drug use, yet it is common in low-income women living with HIV (WLWH) and increases cardiac dysfunction.We recruited unsheltered and unstably housed WLWH from San Francisco community venues to participate in a six-month cohort study investigating linkages between drug use, inflammation, and cardiac dysfunction.Adjusting for CVD risk factors, co-infections, medications, and menopause, we examined the effects of toxicology-confirmed drug use and inflammation (C-reactive protein, sCD14, sCD163 and sTNFR2) on levels of NT-proBNP, a biomarker of cardiac stretch and HF.Among 74 WLWH, the median age was 53 years and 45 % were Black. At baseline, 72 % of participants had hypertension. Substances used included tobacco (65 %), cannabis (53 %), cocaine (49 %), methamphetamine (31 %), alcohol (28 %), and opioids (20 %). Factors significantly associated with NT-proBNP included cannabis use (Adjusted Relative Effect [ARE]: -39.6 %) and sTNFR2 (ARE: 65.5 %). Adjusting for heart failure and restricting analyses to virally suppressed persons did not diminish effects appreciably. Cannabis use was not significantly associated with sTNFR2 and did not change the association between sTNFR2 and NT-proBNP.Among polysubstance-using WLWH, NT-proBNP levels signaling cardiac stretch were positively associated with sTNFR2, but 40 % lower in people who used cannabis. Whether results suggest that cardiovascular pathways associated with cannabis use mitigate cardiac stress and dysfunction independent of inflammation in WLWH who use multiple substances merits further investigation.

Pregnancy confers unique immune responses to infection and vaccination across gestation. To date, there is limited data comparing vaccine versus infection-induced nAb to COVID-19 variants in mothers during pregnancy. We analyzed paired maternal and cord plasma samples from 60 pregnant individuals. Thirty women vaccinated with mRNA vaccines were matched with 30 naturally infected women by gestational age of exposure. Neutralization activity against the five SARS-CoV-2 Spike sequences was measured by a SARS-CoV-2 pseudotyped Spike virion assay. Effective nAbs against SARS-CoV-2 were present in maternal and cord plasma after both infection and vaccination. Compared to wild type or Alpha variant Spike, these nAbs were less effective against the Kappa, Delta, and Mu Spike variants. Vaccination during the third trimester induced higher nAb levels at delivery than infection during the third trimester. In contrast, vaccine-induced nAb levels were lower at the time of delivery compared to infection during the first trimester. The transfer ratio (cord nAb level/maternal nAb level) was greatest in mothers vaccinated in the second trimester. SARS-CoV-2 vaccination or infection in pregnancy elicit effective nAbs with differing neutralization kinetics that is impacted by gestational time of exposure. Vaccine induced neutralizing activity was reduced against the Delta, Mu, and Kappa variants.Graphic abstract

Pregnancy confers unique immune responses to infection and vaccination across gestation. To date, there are limited data comparing vaccine- and infection-induced neutralizing Abs (nAbs) against COVID-19 variants in mothers during pregnancy. We analyzed paired maternal and cord plasma samples from 60 pregnant individuals. Thirty women vaccinated with mRNA vaccines (from December 2020 through August 2021) were matched with 30 naturally infected women (from March 2020 through January 2021) by gestational age of exposure. Neutralization activity against the 5 SARS-CoV-2 spike sequences was measured by a SARS-CoV-2-pseudotyped spike virion assay. Effective nAbs against SARS-CoV-2 were present in maternal and cord plasma after both infection and vaccination. Compared with WT spike protein, these nAbs were less effective against the Delta and Mu spike variants. Vaccination during the third trimester induced higher cord-nAb levels at delivery than did infection during the third trimester. In contrast, vaccine-induced nAb levels were lower at the time of delivery compared with infection during the first trimester. The transfer ratio (cord nAb level divided by maternal nAb level) was greatest in mothers vaccinated in the second trimester. SARS-CoV-2 vaccination or infection in pregnancy elicits effective nAbs with differing neutralization kinetics that are influenced by gestational time of exposure.

Acute liver injury (ALI) is seen in conjunction with elevated iron concentrations in the setting of acute iron toxicity. However, occult or delayed presentations of iron toxicity can be difficult to identify clinically and there is limited data describing iron concentrations in ALI without a confirmed history of iron overdose. This was a single center observational before-and-after study of adult patients who developed acute liver injury during hospitalization. Patients with a serum ALT 500 U/L were identified by a daily hospital laboratory report and met inclusion if the ALT 80 U/L at the time of admission, no history of overdose (iron, acetaminophen, or other ingestion), and no underlying liver disease. Serum AST, iron, and ferritin concentrations were obtained from blood samples at the time of admission and at peak serum ALT. Ten patients met inclusion criteria. The median age was 69 years old and 60% were male. There was a significant difference in serum AST (p = 0.005), serum ALT (p = 0.005), and ferritin (p = 0.005) before and after development of ALI. Serum iron concentrations were not clinically or significantly different (median: 23 mcg/dL vs 27 mcg/dL, p = 0.8). In this cohort of patients with non-iron induced acute liver injury, serum iron concentrations did not significantly change with the observed rise in aminotransferases. These data help to further characterize patterns of serum iron concentrations in patients with ALI.

Background Individuals infected with HIV have an increased risk of developing cardiovascular disease; yet, the underlying mechanisms remain unknown. Recent evidence has implicated the Tie‐2 tyrosine kinase receptor system and its associated ligands ANG1 (angiopoietin 1) and ANG2 (angiopoietin 2) in maintaining vascular homeostasis. In the general population, lower ANG1 levels and higher ANG2 levels are strongly correlated with the development of cardiovascular disease. In this study, we aim to investigate the associations of HIV infection with angiopoietin levels and endothelial dysfunction. Methods and Results In this cross‐sectional study, we compared measures of ANG1, ANG2, and endothelial dysfunction using flow‐mediated vasodilation of the brachial artery in 39 untreated subjects infected with HIV, 47 treated subjects infected with HIV, and 46 uninfected subjects from the SCOPE (Observational Study of the Consequences of the Protease Inhibitor Era) cohort. Compared with uninfected controls, treated individuals infected with HIV had 53.1% lower mean ANG1 levels ( P P P P P P =0.05). In contrast, HIV status, ANG1 levels, and ANG2 levels were not associated with macrovascular dysfunction as measured by flow‐mediated dilatation and brachial artery diameter, 2 other measures of vascular homeostasis. Conclusions HIV infection affects the balance between levels of ANG1 and ANG2 and may disturb endothelial homeostasis through disruption of vascular homeostasis. Individuals with treated HIV had decreased ANG1 levels and similar ANG2 levels, whereas individuals with untreated HIV had similar ANG1 levels and increased ANG2 levels, suggesting that treatment status may alter the balance between ANG1 and ANG2. HIV also promotes endothelial dysfunction via impairment of microvascular dysfunction, independent of the Tie‐2 receptor system; the finding of worse microvascular dysfunction in the setting of treated HIV infection may reflect the impact of viral persistence on the microvasculature or toxicities of specific antiretroviral regimens. Further research to clarify the mechanism of HIV‐mediated endothelial dysfunction is necessary to advance treatment of cardiovascular complications of HIV infection.

The 2019 coronavirus pandemic has led to the deaths of hundreds of thousands of individuals worldwide. The most frequent causes include complications of sepsis, acute respiratory failure, and cardi...

OBJECTIVETo investigate maternal immunoglobulins’ (IgM, IgG) response to SARS-CoV-2 infection during pregnancy and IgG transplacental transfer, to characterize neonatal antibody response to SARS-CoV-2 infection, and to longitudinally follow actively- and passively-acquired SARS-CoV-2 antibodies in infants.DESIGNA prospective observational study.SETTINGA public healthcare system in Santa Clara County (CA, USA).PARTICIPANTSWomen with SARS-CoV-2 infection during pregnancy and their infants were enrolled between April 15, 2020 and March 31, 2021.OUTCOMESSARS-CoV-2 serology analyses in the cord and maternal blood at delivery and longitudinally in infant blood between birth and 28 weeks of life.RESULTSOf 145 mothers who tested positive for SARS-CoV-2 during pregnancy, 86 had symptomatic infections: 78 with mild-moderate symptoms, and eight with severe-critical symptoms. Of the 147 newborns, two infants showed seroconversion at two weeks of age with high levels of IgM and IgG, including one premature infant with confirmed intrapartum infection. The seropositivity rates of the mothers at delivery was 65% (95% CI 0.56-0.73) and the cord blood was 58% (95% CI 0.49-0.66). IgG levels significantly correlated between the maternal and cord blood (Rs= 0.93, p< 0.0001). IgG transplacental transfer ratio was significantly higher when the first maternal positive PCR was 60-180 days before delivery compared to CONCLUSIONSMaternal SARS-CoV-2 IgG is efficiently transferred across the placenta when infections occur more than two months before delivery. Maternally-derived passive immunity may protect infants up to six months of life. Neonates mount a strong antibody response to perinatal SARS-CoV-2 infection.

The kinetics of IgG avidity maturation during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was studied. The IgG avidity assay, using a novel label-free immunoassay technology, revealed a strong correlation between IgG avidity and days since symptom onset. Peak readings were significantly higher in severe than mild disease cases.

Background Biological variation studies have shown that the complete blood count (CBC) has narrow within-individual variation and wide group variation, indicating that the use of reference intervals (RIs) is challenging. The aim of this study was to examine differences in CBC RIs according to race/ethnicity in a multiethnic population at a hospital in San Francisco in hopes of improving the medical utility of CBC testing. Methods Subject data were obtained by screening CBC results from the medical records of outpatients meeting certain criteria who visited Zuckerberg San Francisco General Hospital from April 2017 to January 2018. From these records, sex- and race/ethnicity-specific CBC RIs were calculated as the 2.5th to 97.5th percentiles. Results From a total of 552 subjects, 47.9% were male (65 White, 50 Black, 71 Hispanic and 54 Asian) and 52.1% were female (51 White, 39 Black, 122 Hispanic and 72 Asian). The RIs of neutrophil, lymphocyte and eosinophil counts; and hemoglobin, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) showed significant differences (p Conclusions Race/ethnicity-specific CBC RIs should be taken into consideration in a multiethnic population to better interpret patient status and make progress toward precision medicine.

Background Cardiac troponin (cTn) is a complex of three subunits (T, I, and C), with some studies reporting that ~5–10% is cytosolic and unbound (‘free’). It has been hypothesized that free cTn is released before complex and before or without cell death dependent on the severity of ischemia . In this context, new generation assays that can discriminate free, binary (IC) and ternary (TIC) complex forms may aid to differentiate between type 1 myocardial infarction (MI) and cTn elevations due to different etiologies, e.g. demand ischemia and type 2 MI. Methods Serial plasma samples from six type 1 MI patients and twenty-seven patients with other cTnI elevations, e.g. due to demand ischemia and type 2 MI, were analyzed using high-sensitivity ET Healthcare Pylon assays for total cTnI, complex cTnI (IC and TIC), and cTnTIC. The specificity of the anti-cTnT antibody in the cTnTIC assay was such that only full-size cTnTIC is detected. In vitro stability of different cTnI forms was assessed by spiking free cTnI and cTnTIC in cTnI-free serum, incubating at 4 or 37 °C, and measuring different cTnI forms over 0–182 h. Presence of cytosolic free cTnI was evaluated on fixed rat cardiac tissue using an antibody against free cTnI. Results Pylon assays for total and complex cTnI tracked well over time with each other and gave similar results, both for type 1 MI and non-type 1 MI patients, indicating that the vast majority was complex cTnI. As a minority of complex cTnI was full-size cTnTIC, this indicated that complex cTnI mainly consisted of a degraded form of cTnTIC (low-molecular weight cTnTIC) and/or cTnIC. Full-size cTnTIC was more abundant in early compared to late samples. In vitro studies indicated that free cTnI and cTnTIC are not stable at 37 °C (28% and 11% recovery after 24 h, respectively) and this is also true to some extent for cTnTIC at 4 °C (60% recovery after 24 h). Free cTnI was not readily detected in rat cardiac tissue. Conclusions In agreement with type 1 MI, cTnI in samples of patients with cTnI elevations due to other etiologies is found predominantly as complex cTnI, of which some is full-size cTnTIC. In most cases, assays for total and complex cTnI indicated there was little free cTnI; however, its presence cannot be completely excluded, due to the inability of its direct measurement and limited stability.

BackgroundThe laboratory-based methods to measure the SARS-CoV-2 humoral response include virus neutralization tests (VNTs) to determine antibody neutralization potency. For ease of use and universal applicability, surrogate virus neutralization tests (sVNTs) based on antibody-mediated blockage of molecular interactions have been proposed.MethodsA surrogate virus neutralization test established on a label-free immunoassay platform (LF-sVNT). The LF-sVNT analyzes the binding ability of RBD to ACE2 after neutralizing RBD with antibodies in serum.ResultsThe LF-sVNT neutralizing antibody titers (IC50) were determined from serum samples (n=246) from COVID-19 patients (n=113), as well as the IgG concentrations and the IgG avidity indices. Although there is variability in the kinetics of the IgG concentrations and neutralizing antibody titers between individuals, there is an initial rise, plateau and then in some cases a gradual decline at later timepoints after 40 days post-symptom onset. The IgG avidity indices, in the same cases, plateau after the initial rise and did not show a decline.ConclusionsThe LF-sVNT can be a valuable tool in clinical laboratories for the assessment of the presence of neutralizing antibodies to COVID-19. This study is the first to provide longitudinal neutralizing antibody titers beyond 200 days post-symptom onset. Despite the decline of IgG concentration and neutralizing antibody titer, IgG avidity index increases, reaches a plateau and then remains constant up to 8 months post-infection. The decline of antibody neutralization potency can be attributed to the reduction in antibody quantity rather than the deterioration of antibody avidity, a measure of antibody quality.SummaryA surrogate virus neutralization test established on a label-free immunoassay platform (LF-sVNT). Using the LF-sVNT and other assays, 246 serum samples from 113 COVID-19 patients were measured. We observed the time course of antibody characteristics beyond 200 days post-symptom onset.

Background As global confirmed cases and deaths from coronavirus disease 2019 (COVID-19) surpass 100 and 2.2 million, respectively, quantifying the effects of the widespread treatment of remdesivir (GS-5734, Veklury) and the steroid dexamethasone is becoming increasingly important. Limited pharmacokinetic studies indicate that remdesivir concentrations in serum decrease quickly after dosing, so its primary serum metabolite GS-441524 may have more analytical utility. Objectives We developed and validated a method to quantify remdesivir, its metabolite GS-441524 and dexamethasone in human serum. Methods We used LC-MS/MS and applied the method to 23 serum samples from seven patients with severe COVID-19. Results The method has limits of detection of 0.0375 ng/mL for remdesivir, 0.375 ng/mL for GS-441524 and 3.75 ng/mL for dexamethasone. We found low intra-patient variability, but significant inter-patient variability, in remdesivir, GS-441524 and dexamethasone levels. Conclusions The significant inter-patient variability highlights the importance of therapeutic drug monitoring of COVID-19 patients and possible dose adjustment to achieve efficacy.

Serosurveillance provides a unique opportunity to quantify the proportion of the population that has been exposed to pathogens. Here, we developed and piloted Serosurveillance for Continuous, ActionabLe Epidemiologic Intelligence of Transmission (SCALE-IT), a platform through which we systematically tested remnant samples from routine blood draws in two major hospital networks in San Francisco for SARS-CoV-2 antibodies during the early months of the pandemic. Importantly, SCALE-IT allows for algorithmic sample selection and rich data on covariates by leveraging electronic medical record data. We estimated overall seroprevalence at 4.2%, corresponding to a case ascertainment rate of only 4.9%, and identified important heterogeneities by neighborhood, homelessness status, and race/ethnicity. Neighborhood seroprevalence estimates from SCALE-IT were comparable to local community-based surveys, while providing results encompassing the entire city that have been previously unavailable. Leveraging this hybrid serosurveillance approach has strong potential for application beyond this local context and for diseases other than SARS-CoV-2.

Race and Genetic Ancestry in Medicine U.S. health inequities won’t be eliminated by abandoning the use of race and ethnicity in research and clinical practice, since these variables capture key epi...