Exploratory factor analysis yields grouping of brain injury biomarkers significantly associated with outcomes in neonatal and pediatric ECMO.

In this two-center prospective cohort study of children on ECMO, we assessed a panel of plasma brain injury biomarkers using exploratory factor analysis (EFA) to evaluate their interplay and association with outcomes. Biomarker concentrations were measured daily for the first 3 days of ECMO support in 95 participants. Unfavorable composite outcome was defined as in-hospital mortality or discharge Pediatric Cerebral Performance Category > 2 with decline ≥ 1 point from baseline. EFA grouped 11 biomarkers into three factors. Factor 1 comprised markers of cellular brain injury (NSE, BDNF, GFAP, S100ß, MCP1, VILIP-1, neurogranin); Factor 2 comprised markers related to vascular processes (vWF, PDGFRß, NPTX1); and Factor 3 comprised the BDNF/MMP-9 cellular pathway. Multivariable logistic models demonstrated that higher Factor 1 and 2 scores were associated with higher odds of unfavorable outcome (adjusted OR 2.88 [1.61, 5.66] and 1.89 [1.12, 3.43], respectively). Conversely, higher Factor 3 scores were associated with lower odds of unfavorable outcome (adjusted OR 0.54 [0.31, 0.88]), which is biologically plausible given the role of BDNF in neuroplasticity. Application of EFA on plasma brain injury biomarkers in children on ECMO yielded grouping of biomarkers into three factors that were significantly associated with unfavorable outcome, suggesting future potential as prognostic instruments.

Higher levels of brain injury biomarker tau are associated with unfavorable outcomes in patients supported with ECMO following cardiac arrest.

Aim: We sought to determine if higher plasma levels of brain injury biomarkers neurofilament light (NfL), phosphorylated tau 181 (pT181), tau, and ubiquitin C-terminal hydrolase L1 (UCHL1) were associated with unfavorable outcomes in children supported on extracorporeal membrane oxygenation (ECMO) with and without preceding cardiac arrest. Methods: We conducted a secondary analysis of a two-center prospective observational study of ECMO patients 0-<18 years. Plasma concentrations of NfL, pT181, tau, and UCHL1 were measured on ECMO days 1, 2 and 3. Unfavorable outcome was defined as in-hospital mortality or discharge Pediatric Cerebral Performance Category (PCPC) >2 with decline from baseline PCPC among survivors. Results: Among 88 children on ECMO, mean tau levels were significantly higher on each of the first three ECMO days in children who underwent extracorporeal cardiopulmonary resuscitation (ECPR) compared to those with non-ECPR cardiac arrest or with no cardiac arrest preceding ECMO. Higher ECMO day 1 tau levels were significantly associated with increased hazard of unfavorable outcome in unadjusted (HR, 1.35, 95% CI 1.09-1.66) and adjusted (HR, 1.42; 95% CI 1.13-1.79) models. Higher levels of NfL or pT181 were not associated with increased hazard for unfavorable outcome in multivariable models. UCHL1 values were outside of detectable limits and thus deferred from analysis. Conclusions: Levels of tau were significantly associated with increased hazard of death or unfavorable neurologic outcome in unadjusted and adjusted models. Biomarkers of brain injury, particularly tau, may aid in detection of neurologic injury and neuroprognostication in patients on ECMO with and without preceding cardiac arrest.

Sensitive Serology Measurements in the Saliva of Individuals with COVID-19 Symptoms Using a Multiplexed Immunoassay.

BACKGROUND: There are numerous benefits to performing salivary serology measurements for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen for coronavirus disease 2019 (COVID-19). Here, we used a sensitive multiplex serology assay to quantitate salivary IgG against 4 SARS-CoV-2 antigens: nucleocapsid, receptor-binding domain, spike, and N-terminal domain. METHODS: We used single samples from 90 individuals with COVID-19 diagnosis collected at 0 to 42 days postsymptom onset (PSO) and from 15 uninfected control subjects. The infected individuals were segmented in 4 groups (0-7 days, 8-14 days, 15-21 days, and >21 days) based on days PSO, and values were compared to controls. RESULTS: Compared to controls, infected individuals showed higher levels of antibodies against all antigens starting from 8 days PSO. When applying cut-offs with at least 93.3% specificity at every time interval segment, nucleocapsid protein serology had the best sensitivity at 0 to 7 days PSO (60% sensitivity [35.75% to 80.18%], ROC area under the curve [AUC] = 0.73, P = 0.034). Receptor-binding domain serology had the best sensitivity at 8 to 14 days PSO (83.33% sensitivity [66.44%-92.66%], ROC AUC = 0.90, P < 0.0001), and all assays except for N-terminal domain had 92% sensitivity (75.03%-98.58%) at >14 days PSO. CONCLUSIONS: This study shows that our multiplexed immunoassay can distinguish infected from uninfected individuals and reliably (93.3% specificity) detect seroconversion (in 60% of infected individuals) as early as the first week PSO, using easy-to-collect saliva samples.

Saliva-based SARS-CoV-2 serology using at-home collection kits returned via mail.

Serology provides tools for epidemiologic studies, and may have a role in vaccine prioritization and selection. Automated serologic testing of saliva, especially specimens that are self-collected at home and sent to a laboratory via the mail without refrigeration, could be a highly-scalable strategy for population-wide testing. In this prospective study, non-vaccinated patients were recruited after PCR testing to self-collect saliva and return their specimens via mail. Longitudinal specimens were analyzed in order to monitor seroconversion in the weeks after a diagnostic PCR test for SARS-CoV-2. Diverse users self-collected saliva and returned specimens via mail in compliance with shipping regulations. At our pre-established threshold (0.963 AU/mL), salivary IgG reactivity to full-length spike protein achieved 95.8% sensitivity and 92.4% specificity at 2-4 weeks after diagnostic testing, which is comparable to the typical sensitivity and specificity achieved for serum testing. Reactivity to N antigen also was detected with 92.6% sensitivity and 90.7% specificity at 4-8 weeks after diagnostic testing. Moreover, serologic testing for endemic coronaviruses performed in multiplex with SARS-CoV-2 antigens has the potential to identify samples that may require retesting due to effects of pre-analytical factors. The easy-to-use saliva collection kit, coupled with thresholds for positivity and methods of flagging samples for retest, provides a framework for large-scale serosurveillance of SARS-CoV-2.

Quantitative serology for SARS-CoV-2 using self-collected saliva and finger-stick blood.

Convenient and widespread serology testing may alter the trajectory of the COVID-19 pandemic. This study seeks to leverage high-throughput, multiplexed serologic assays, which have been adopted as benchmarks for vaccine efficacy, to support large-scale surveys of SARS-CoV-2 immunity using finger-stick blood and/or saliva. Specifically, we optimized MSD's serology assays, which were analytically validated for serum, to test self-collected finger-stick blood and saliva samples to identify prior infection. We show that these assays can be used with FDA-registered specimen collection devices to obtain quantitative measurements for self-collected samples. First, we show that salivary antibodies are stable without refrigeration or preservatives for at least 5 days. We selected classification thresholds for antibodies against SARS-CoV-2 N, RBD and Spike in finger-stick blood and saliva that provided 98% specificity in a set of individuals without known COVID-19 exposure. Using matched samples, we show that testing of saliva and finger-stick blood equivalently identified individuals with humoral responses to CoV-2 antigens. Moreover, we piloted a simple saliva collection kit that can be used to safely send samples through the mail using written instructions only. This work establishes key parameters to robustly assay self-collected finger-stick blood and saliva using quantitative immunoassays that could support large-scale serology testing.

Measurement of Severe Acute Respiratory Syndrome Coronavirus 2 Antigens in Plasma of Pediatric Patients With Acute Coronavirus Disease 2019 or Multisystem Inflammatory Syndrome in Children Using an Ultrasensitive and Quantitative Immunoassay.

BACKGROUND: Detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens in blood has high sensitivity in adults with acute coronavirus disease 2019 (COVID-19), but sensitivity in pediatric patients is unclear. Recent data suggest that persistent SARS-CoV-2 spike antigenemia may contribute to multisystem inflammatory syndrome in children (MIS-C). We quantified SARS-CoV-2 nucleocapsid (N) and spike (S) antigens in blood of pediatric patients with either acute COVID-19 or MIS-C using ultrasensitive immunoassays (Meso Scale Discovery). METHODS: Plasma was collected from inpatients (<21 years) enrolled across 15 hospitals in 15 US states. Acute COVID-19 patients (n = 36) had a range of disease severity and positive nasopharyngeal SARS-CoV-2 RT-PCR within 24 hours of blood collection. Patients with MIS-C (n = 53) met CDC criteria and tested positive for SARS-CoV-2 (RT-PCR or serology). Controls were patients pre-COVID-19 (n = 67) or within 24 hours of negative RT-PCR (n = 43). RESULTS: Specificities of N and S assays were 95-97% and 100%, respectively. In acute COVID-19 patients, N/S plasma assays had 89%/64% sensitivity; sensitivities in patients with concurrent nasopharyngeal swab cycle threshold (Ct) ≤35 were 93%/63%. Antigen concentrations ranged from 1.28-3844 pg/mL (N) and 1.65-1071 pg/mL (S) and correlated with disease severity. In MIS-C, antigens were detected in 3/53 (5.7%) samples (3 N-positive: 1.7, 1.9, 121.1 pg/mL; 1 S-positive: 2.3 pg/mL); the patient with highest N had positive nasopharyngeal RT-PCR (Ct 22.3) concurrent with blood draw. CONCLUSIONS: Ultrasensitive blood SARS-CoV-2 antigen measurement has high diagnostic yield in children with acute COVID-19. Antigens were undetectable in most MIS-C patients, suggesting that persistent antigenemia is not a common contributor to MIS-C pathogenesis.

Ultrasensitive assay for saliva-based SARS-CoV-2 antigen detection.

OBJECTIVES: Widespread SARS-CoV-2 testing is invaluable for identifying asymptomatic/pre-symptomatic individuals. There remains a technological gap for highly reliable, easy, and quick SARS-CoV-2 diagnostic tests suitable for frequent mass testing. Compared to nasopharyngeal (NP) swab-based tests, saliva-based methods are attractive due to easier and safer sampling. Current saliva-based SARS-CoV-2 rapid antigen tests (RATs) are hindered by limited analytical sensitivity. Here, we report one of the first ultrasensitive, saliva-based SARS-CoV-2 antigen assays with an analytical sensitivity of <0.32 pg/mL, corresponding to four viral RNA copies/µL, which is comparable to that of PCR-based tests. METHODS: Using the novel electrochemiluminescence (ECL)-based immunoassay, we measured the SARS-CoV-2 nucleocapsid (N) antigen concentration in 105 salivas, obtained from non-COVID-19 and COVID-19 patients. We then verified the results with a second, independent cohort of 689 patients (3.8% SARS-CoV-2 positivity rate). We also compared our method with a widely used point-of-care rapid test. RESULTS: In the first cohort, at 100% specificity, the sensitivity was 92%. Our assay correctly identified samples with viral loads up to 35 CT cycles by saliva-based PCR. Paired NP swab-based PCR results were obtained for 86 cases. Our assay showed high concordance with saliva-based and NP swab-based PCR in samples with negative (<0.32 pg/mL) and strongly positive (>2 pg/mL) N antigen concentrations. In the second cohort, at 100% specificity, sensitivity was also 92%. Our assay is about 700-fold more sensitive than the Abbott Panbio Rapid Test. CONCLUSIONS: We demonstrated the ultrasensitivity and specificity assay and its concordance with PCR. This novel assay is especially valuable when compliance to frequent swabbing may be problematic.

Measurement of SARS-CoV-2 antigens in plasma of pediatric patients with acute COVID-19 or MIS-C using an ultrasensitive and quantitative immunoassay.

BACKGROUND: Detection of SARS-CoV-2 antigens in blood has high sensitivity in adults with acute COVID-19, but sensitivity in pediatric patients is unclear. Recent data suggest that persistent SARS-CoV-2 spike antigenemia may contribute to multisystem inflammatory syndrome in children (MIS-C). We quantified SARS-CoV-2 nucleocapsid (N) and spike (S) antigens in blood of pediatric patients with either acute COVID-19 or MIS-C using ultrasensitive immunoassays (Meso Scale Discovery). METHODS: Plasma was collected from inpatients (<21 years) enrolled across 15 hospitals in 15 US states. Acute COVID-19 patients (n=36) had a range of disease severity and positive nasopharyngeal SARS-CoV-2 RT-PCR within 24 hours of blood collection. Patients with MIS-C (n=53) met CDC criteria and tested positive for SARS-CoV-2 (RT-PCR or serology). Controls were patients pre-COVID-19 (n=67) or within 24h of negative RT-PCR (n=43). RESULTS: Specificities of N and S assays were 95-97% and 100%, respectively. In acute COVID-19 patients, N/S plasma assays had 89%/64% sensitivity, respectively; sensitivity in patients with concurrent nasopharyngeal swab cycle threshold (Ct) ≤ 35 were 93%/63%. Antigen concentrations ranged from 1.28-3,844 pg/mL (N) and 1.65-1,071 pg/mL (S) and correlated with disease severity. In MIS-C, antigens were detected in 3/53 (5.7%) samples (3 N-positive: 1.7, 1.9, 121.1 pg/mL; 1 S-positive: 2.3 pg/mL); the patient with highest N had positive nasopharyngeal RT-PCR (Ct 22.3) concurrent with blood draw. CONCLUSIONS: Ultrasensitive blood SARS-CoV-2 antigen measurement has high diagnostic yield in children with acute COVID-19. Antigens were undetectable in most MIS-C patients, suggesting that persistent antigenemia is not a common contributor to MIS-C pathogenesis. KEY POINTS: In a U.S. pediatric cohort tested with ultrasensitive immunoassays, SARS-CoV-2 nucleocapsid antigens were detectable in most patients with acute COVID-19, and spike antigens were commonly detectable. Both antigens were undetectable in almost all MIS-C patients.