1005. COVID-19 At-Home Capillary Blood Specimen Collection Pilot – Gaining Insight into Independent Self- Collection of Blood Specimens and COVID-19 Within the Veteran Population

Background The VA Million Veteran Program (MVP) studies what factors influence Veteran health. Current procedures involve collection of venous blood at MVP enrollment sites. To examine home specimen collection options, MVP performed a pilot study comparing two blood specimen collection devices and evaluated SARS-CoV-2 antibody assays to determine known COVID-19 infection or vaccination. Methods A sub-sample of MVP Veteran participants were asked to self-collect a capillary blood specimen using the Neoteryx Mitra Clamshell (up to 120uL dried blood) or Tasso-SST (up to 200uL liquid blood) per the vendor instructions. Veterans were randomly assigned to a device prior to consent. Eligibility included 30% of Veterans with known COVID-19 diagnosis or vaccination and sampling time was variable from these events. Veterans rated their device experience and shipped collected specimens directly to an MVP laboratory. Mitra tip (4) blood was eluted in 1 mL of 0.9% normal saline for 1 hour at room temperature shaking at 300 rpm. Tasso tubes were centrifuged per vendor instructions. All samples were stored at -80°C until tested with SARS-Cov-2 antibody (Ab) assays (InBios Spike IgG, BioRad Nucleocapsid (NC) Total Ab, Abbott NC IgG, and Abbott Spike IgG II) per vendor instructions. Results 312 MVP participants consented to the pilot (52%) of which 136 (43.6%) were sent Mitra and 176 (56.4%) were sent Tasso-SST (Table 1). Participants rated the Mitra Tasso-SST equally on average as 4.4 on a 0-5 usability scale. The Abbott IgG II assay had the highest sensitivity across both devices (87% Mitra and 98% Tasso-SST) for detecting known COVID infection and/or vaccination. The InBios IgG assay with the Tasso-SST had the best sensitivity (97%) and specificity (80%) for detecting known COVID-19 infection and/or vaccination (Table 2). Table 1. COVID-19 At-Home Capillary Blood Specimen Collection Pilot Outcomes Conclusion Veterans successfully collected their own specimens and had no strong preference for either device. The Tasso-SST combined with the InBios Spike IgG assay provided the highest combination of sensitivity and specificity. Limitations included one collection device per subject, varied timing of testing, unknown infection or vaccination status among some, and Tasso collection volume and Mitra whole blood dilution may have affected comparison across assays or performance. Disclosures All Authors: No reported disclosures

Extracorporeal Arteriovenous Ultrasound Measurement of Cardiac Output in Small Children

Editor’s Perspective What We Already Know about This Topic To date, there are not clinically practical, accurate, and precise noninvasive methods for measuring cardiac output in small children What This Article Tells Us That Is New This study describes a noninvasive method by which ultrasound can be used in small children to determine cardiac output with good precision After surgery in 43 small children for repair of atrial or ventricular septal defects, cardiac output measurements performed using saline bolus injections and ultrasound detection of the expected blood dilution showed similar precision for measuring cardiac output as a cardiac outputs measured using periaortic flow probe Background Technology for cardiac output (CO) and blood volume measurements has been developed based on blood dilution with a small bolus of physiologic body temperature saline, which, after transcardiopulmonary mixing, is detected with ultrasound sensors attached to an extracorporeal arteriovenous loop using existing central venous and peripheral arterial catheters. This study aims to compare the precision and agreement of this technology to measure cardiac output with a reference method, a perivascular flow probe placed around the aorta, in young children. The null hypothesis is that the methods are equivalent in precision, and there is no bias in the cardiac output measurements. Methods Forty-three children scheduled for cardiac surgery were included in this prospective single-center comparison study. After corrective cardiac surgery, five consecutive repeated cardiac output measurements were performed simultaneously by both methods. Results A total of 215 cardiac output measurements were compared in 43 children. The mean age of the children was 354 days (range, 30 to 1,303 days), and the mean weight was 7.1 kg (range, 2.7 to 13.6 kg). The precision assessed as two times the coefficient of error was 3.6% for the ultrasound method and 5.0% for the flow probe. Bias (mean COultrasound 1.28 l/min − mean COflow probe 1.20 l/min) was 0.08 l/min, limits of agreement was ±0.32 l/min, and the percentage error was 26.6%. Conclusions The technology to measure cardiac output with ultrasound detection of blood dilution after a bolus injection of saline yields comparable precision as cardiac output measurements by a periaortic flow probe. The difference in accuracy in the measured cardiac output between the methods can be explained by the coronary blood flow, which is excluded in the cardiac output measurements by the periaortic flow probe.

Considering Blood Dilution improves the Precision of Continuous Whole Blood Glucose Measurements

Background:One major advantage of automated over manual clamps are continuous measurements of blood glucose concentrations (BG) allowing frequent adaptations in glucose infusion rates (GIR). However, BG measurements might be affected by changes in blood dilution. ClampArt®, a modern automated clamp device, corrects BG measurements for blood dilution, but the impact of this correction is unclear.Methods:The authors performed a retrospective analysis of BG during glucose clamps comparing values with a fixed dilution factor with those corrected for the actual blood dilution.Results:Clamp quality substantially improved with the consideration of blood dilution: Mean accuracy fell from 8.1% ± 2.9% to 4.1% ± 0.8%, precision improved from 9.6 ± 3.6 mg/dl to 3.7 ± 1.3 mg/dl and control deviation from −2.6 ± 4.2 mg/dl to 0.2 ± 0.2 mg/dl.Conclusions:Correcting continuous BG measurements for blood dilution significantly increases BG measurement and clamp quality.

Determination of Al, Be, Cd, Co, Cr, Mn, Ni, Pb, Se and Tl in whole blood by atomic absorption spectrometry without preliminary sample digestion

Methods of whole blood trace element determination by Graphite furnace atomic absorption spectrometry (in the variant of Zeeman’s modulation polarization spectrometry) have been proposed. They do not require preliminary sample digestion. Furnace programs, modifiers and blood dilution factors were optimized. Seronorm™ human whole blood reference materials were used for validation. Dynamic ranges (for undiluted blood samples) were: Al 8 ¸ 210 мg/L; Be 0.3 ¸ 50 мg/L; Cd 0.2 ¸ 75 мg/L; Сo 5 ¸ 350 мg/L; Cr 10 ¸ 100 мg/L; Mn 6 ¸ 250 мg/L; Ni 10 ¸ 350 мg/L; Pb 3 ¸ 240 мg/L; Se 10 ¸ 500 мg/L; Tl 2 ¸ 600 мg/L. Precision (RSD) for the middle of dynamic range ranged from 5% for Mn to 11 for Se.

The Resusciatative Fluid You Chose May Potentiate Bleeding.

Trauma is the leading cause of death in the younger population in the United States, frequently from the development of hemorrhagic shock. Controversy exists over the type of volume resuscitation to be used (dilutions ranging up to 66%) in hemorrhagic shock for restoring hemodynamic stability. Trauma results in massive exposure of tissue factor to the circulation and explosive amounts of thrombin being generated. We studied the effect of various resuscitative formulas to blood coagulation, specifically thrombin generation and fibrin formation, in a controlled setting using corn trypsin inhibited whole blood initiated with a 5pM stimulus of tissue factor. Thrombin generation measured as its complex with antithrombin III (TAT) was evaluated periodically over a time course of 20 min. Fibrin clots were collected and weighed. We investigated four diluents (0.9% NaCl (NS), lactated Ringer’s solution (LR), 6% hydroxyethyl starch (HES) and 3% NaCl (HS)) each at a 0,10, 20, 30, 40, 50 and 60% blood dilution. At a 10% dilution TAT generation was in the order of LR (−4%) < HES (−8%)< NS and HS (−12%). Diluting by 20% resulted in further decreases of TAT formation. The fibrin clot mass decreased dramatically with a 20% dilution for NS (−42%) and HES (−30%). Conversely, HS produced no change in fibrin mass but effected the largest change in thrombin generation rate (−56%). At a 50% dilution, comparable thrombin generation profiles were obtained for LR, HES and NS (~35% decrease). However, the fibrin masses decreased by 27% with LR, 46% with NS and 74% with HES. No clot formation or thrombin generation was seen with HS at > 20% dilution. This in vitro study shows that: 1) LR has the least effect on thrombin generation and gave higher than anticipated clot weights; 2) HES reduced the fibrin clot mass at higher dilutions; 3) HS abolishes coagulation after a 20% dilution. Overall, both the extent and nature of hemodilution cause profound alterations in the hemostatic mechanism.