PneumoniaCheck, a novel aerosol collection device, permits capture of airborne Mycobacterium tuberculosis and characterisation of the cough aeromicrobiome in people with tuberculosis.

BACKGROUND: Tuberculosis (TB), a major cause of disease and antimicrobial resistance, is spread via aerosols. Aerosols have diagnostic potential and airborne-microbes other than Mycobacterium tuberculosis complex (MTBC) may influence transmission. We evaluated whether PneumoniaCheck (PMC), a commercial aerosol collection device, captures MTBC and the aeromicrobiome of people with TB. METHODS: PMC was done in sputum culture-positive people (≥ 30 forced coughs each, n = 16) pre-treatment and PMC air reservoir (bag, corresponding to upper airways) and filter (lower airways) washes underwent Xpert MTB/RIF Ultra (Ultra) and 16S rRNA gene sequencing (sequencing also done on sputum). In a subset (n = 6), PMC microbiota (bag, filter) was compared to oral washes and bronchoalveolar lavage fluid (BALF). FINDINGS: 54% (7/13) bags and 46% (6/14) filters were Ultra-positive. Sequencing read counts and microbial diversity did not differ across bags, filters, and sputum. However, microbial composition in bags (Sphingobium-, Corynebacterium-, Novosphingobium-enriched) and filters (Mycobacterium-, Sphingobium-, Corynebacterium-enriched) each differed vs. sputum. Furthermore, sequencing only detected Mycobacterium in bags and filters but not sputum. In the subset, bag and filter microbial diversity did not differ vs. oral washes or BALF but microbial composition differed. Bags vs. BALF were Sphingobium-enriched and Mycobacterium-, Streptococcus-, and Anaerosinus-depleted (Anaerosinus also depleted in filters vs. BALF). Compared to BALF, none of the aerosol-enriched taxa were enriched in oral washes or sputum. INTERPRETATION: PMC captures aerosols with Ultra-detectable MTBC and MTBC is more detectable in aerosols than sputum by sequencing. The aeromicrobiome is distinct from sputum, oral washes and BALF and contains differentially-enriched lower respiratory tract microbes.

Detection of pathogenic bacteria and biomarkers in lung specimens from cystic fibrosis patients.

Diagnosing lung infections is often challenging because of the lack of a high-quality specimen from the diseased lung. Since persons with cystic fibrosis are subject to chronic lung infection, there is frequently a need for a lung specimen. In this small, proof of principle study, we determined that PneumoniaCheckTM, a non-invasive device that captures coughed droplets from the lung on a filter, might help meet this need. We obtained 10 PneumoniaCheckTMcoughed specimens and 2 sputum specimens from adult CF patients hospitalized with an exacerbation of their illness. We detected amylase (upper respiratory tract) with an enzymatic assay, surfactant A (lower respiratory tract) with an immunoassay, pathogenic bacteria by PCR, and markers of inflammation by a Luminex multiplex immunoassay. The amylase and surfactant A levels suggested that 9/10 coughed specimens were from lower respiratory tract with minimal upper respiratory contamination. The PCR assays detected pathogenic bacteria in 7 of 9 specimens and multiplex Luminex assay detected a variety of cytokines or chemokines. These data indicate that the PneumoniaCheckTMcoughed specimens can capture good quality lower respiratory tract specimens that have the potential to help in diagnosis, management and understanding of CF exacerbations and other lung disease.

Material strengths of shear-induced platelet aggregation clots and coagulation clots.

Arterial occlusion by thrombosis is the immediate cause of some strokes, heart attacks, and peripheral artery disease. Most prior studies assume that coagulation creates the thrombus. However, a contradiction arises as whole blood (WB) clots from coagulation are too weak to stop arterial blood pressures (> 150 mmHg). We measure the material mechanical properties of elasticity and ultimate strength for Shear-Induced Platelet Aggregation (SIPA) type clots, that form under stenotic arterial hemodynamics in comparison with coagulation clots. The ultimate strength of SIPA clots averaged 4.6 ± 1.3 kPa, while WB coagulation clots had a strength of 0.63 ± 0.3 kPa (p < 0.05). The elastic modulus of SIPA clots was 3.8 ± 1.5 kPa at 1 Hz and 0.5 mm displacement, or 2.8 times higher than WB coagulation clots (1.3 ± 1.2 kPa, p < 0.0001). This study shows that the SIPA thrombi, formed quickly under high shear hemodynamics, is seven-fold stronger and three-fold stiffer compared to WB coagulation clots. A force balance calculation shows a SIPA clot has the strength to resist arterial pressure with a short length of less than 2 mm, consistent with coronary pathology.

Novel tubing connectors reduce ECMO circuit thrombosis.

BACKGROUND: Thrombosis within extracorporeal membrane oxygenation (ECMO) circuits is a common complication that dominates clinical management of patients receiving mechanical circulatory support. Prior studies have identified that over 80% of circuit thrombosis can be attributed to tubing-connector junctions. METHODS: A novel connector was designed that reduces local regions of flow stagnation at the tubing-connector junction to eliminate a primary source of ECMO circuit thrombi. To compare clotting between the novel connectors and the traditional connectors, both in vitro loops and an in vivo caprine model of long-term (48 h) ECMO were used to generate tubing-connector junction clots. RESULTS: In vitro, the traditional connectors uniformly (9/9) formed large thrombi, while novel connectors formed a small thrombus in only one of nine (p < 0.0001). In the long-term goat ECMO circuits, the traditional connectors exhibited more thrombi (p < 0.04), and these thrombi were more likely to protrude into the lumen of the tubing (p < 0.001). CONCLUSION: Both in vitro and in vivo validation experiments successfully recreated circuit thrombosis and demonstrate that the adoption of novel connectors can reduce the burden of circuit thrombosis.

A novel aerosol collection method shows the cough aeromicrobiome of people with tuberculosis is phylogenetically distinct from respiratory tract specimens.

Background: Tuberculosis (TB), a major cause of disease and antimicrobial resistance, is spread via aerosols. Aerosols have diagnostic potential and airborne-microbes other than Mycobacterium tuberculosis complex (MTBC) may influence transmission. We evaluated whether PneumoniaCheck (PMC), a commercial aerosol collection device, captures MTBC and the aeromicrobiome of people with TB. Methods: PMC was done in sputum culture-positive people (≥30 forced coughs each, n=16) pre-treatment and PMC air reservoir (bag, corresponding to upper airways) and filter (lower airways) washes underwent Xpert MTB/RIF Ultra (Ultra) and 16S rRNA gene sequencing (sequencing also done on sputum). In a subset (n=6), PMC microbiota (bag, filter) was compared to oral washes and bronchoalveolar lavage fluid (BALF). Findings: 54% (7/13) bags and 46% (6/14) filters were Ultra-positive. Sequencing read counts and microbial diversity did not differ across bags, filters, and sputum. However, microbial composition in bags (Sphingobium-, Corynebacterium-, Novosphingobium-enriched) and filters (Mycobacterium-, Sphingobium-, Corynebacterium-enriched) each differed vs. sputum. Furthermore, sequencing only detected Mycobacterium in bags and filters but not sputum. In the subset, bag and filter microbial diversity did not differ vs. oral washes or BALF but microbial composition differed. Bags vs. BALF were Sphingobium-enriched and Mycobacterium-, Streptococcus-, and Anaerosinus-depleted (Anaerosinus also depleted in filters vs. BALF). Compared to BALF, none of the aerosol-enriched taxa were enriched in oral washes or sputum. Interpretation: PMC captures aerosols with Ultra-detectable MTBC and MTBC is more detectable in aerosols than sputum by sequencing. The aeromicrobiome is distinct from sputum, oral washes and BALF and contains differentially-enriched lower respiratory tract microbes.

N-Acetyl Cysteine Prevents Arterial Thrombosis in a Dose-Dependent Manner In Vitro and in Mice.

BACKGROUND: Platelet-rich thrombi occlude arteries causing fatal infarcts like heart attacks and strokes. Prevention of thrombi by current antiplatelet agents can cause major bleeding. Instead, we propose using N-acetyl cysteine (NAC) to act against the protein VWF (von Willebrand factor), and not platelets, to prevent arterial thrombi from forming. METHODS: NAC was assessed for its ability to prevent arterial thrombosis by measuring platelet accumulation rate and occlusion time using a microfluidic model of arterial thrombosis with human blood. Acute clot formation, clot stability, and tail bleeding were measured in vivo with the murine modified Folts model. The effect of NAC in the murine model after 6 hours was also measured to determine any persistent effects of NAC after it has been cleared from the blood. RESULTS: We demonstrate reduction of thrombi formation following treatment with NAC in vitro and in vivo. Human whole blood treated with 3 or 5 mmol/L NAC showed delayed thrombus formation 2.0× and 3.7× longer than control, respectively (P<0.001). Blood treated with 10 mmol/L NAC did not form an occlusive clot, and no macroscopic platelet aggregation was visible (P<0.001). In vivo, a 400-mg/kg dose of NAC prevented occlusive clots from forming in mice without significantly affecting tail bleeding times. A lower dose of NAC significantly reduced clot stability. Mice given multiple injections showed that NAC has a lasting and cumulative effect on clot stability, even after being cleared from the blood (P<0.001). CONCLUSIONS: Both preclinical models demonstrate that NAC prevents thrombus formation in a dose-dependent manner without significantly affecting bleeding time. This work highlights a new pathway for preventing arterial thrombosis, different from antiplatelet agents, using an amino acid derivative as an antithrombotic therapeutic.

The incidence and impact of enterotomy during laparoscopic and robotic ventral hernia repair: a nationwide readmissions analysis.

INTRODUCTION: Our aim was to define the national incidence of enterotomy (ENT) during minimally invasive ventral hernia repair (MIS-VHR) and evaluate impact on short-term outcomes. METHODS: The 2016-2018 Nationwide Readmissions Database was queried using ICD-10 codes for MIS-VHR and enterotomy. All patients had 3-months follow-up. Patients were stratified by elective status; patients without ENT (No-ENT) were compared against ENT patients. RESULTS: In total, 30,025 patients underwent LVHR and ENT occurred in 388 (1.3%) patients; 19,188 (63.9%) cases were elective including 244 elective-ENT patients. Incidence was similar between elective versus non-elective cohorts (1.27% vs 1.33%; p = 0.674). Compared to laparoscopy, ENT was more common during robotic procedures (1.2% vs 1.7%; p = 0.004). Comparison of elective-No-ENT vs elective-ENT showed that elective-ENT patients had a longer median LOS (2 vs 5 days; p < 0.001), higher mean hospital cost ($51,656 vs $76,466; p < 0.001), increased rates of mortality (0.3% vs 2.9%; p < 0.001), and higher 3-month readmission (10.1% vs 13.9%; p = 0.048). Non-elective cohort comparison demonstrated non-elective-ENT patients had a longer median LOS (4 vs 7 days; p < 0.001), higher mean hospital cost ($58,379 vs $87,850; p < 0.001), increased rates of mortality (0.7% vs 2.1%;p < 0.001), and higher 3-month readmission (13.6% vs 22.2%; p < 0.001). In multivariable analysis (odds ratio, 95% CI), higher odds of enterotomy were associated with robotic-assisted procedures (1.386, 1.095-1.754; p = 0.007) and older age (1.014, 1.004-1.024; p = 0.006). Lower odds of ENT were associated with BMI > 25 kg/m2 (0.784, 0.624-0.984; p = 0.036) and metropolitan teaching vs metropolitan non-teaching (0.784, 0.622-0.987; p = 0.044). ENT patients (n = 388) were more likely to be readmitted with post-operative infection (1.9% vs 4.1%; p = 0.002) or bowel obstruction (1.0% vs 5.2%;p < 0.001) and more likely to undergo reoperation for intestinal adhesions (0.3% vs 1.0%; p = 0.036). CONCLUSION: Inadvertent ENT occurred in 1.3% of MIS-VHRs, had similar rates between elective and urgent cases, but was more common for robotic procedures. ENT patients had a longer LOS, and increased cost and infection, readmission, re-operation and mortality rates.

The critical role of engineering in the rapid development of COVID-19 diagnostics: Lessons from the RADx Tech Test Verification Core.

Engineering plays a critical role in the development of medical devices, and this has been magnified since 2020 as severe acute respiratory syndrome coronavirus 2 swept over the globe. In response to the coronavirus disease 2019, the National Institutes of Health launched the Rapid Acceleration of Diagnostics (RADx) initiative to help meet the testing needs of the United States and effectively manage the pandemic. As the Engineering and Human Factors team for the RADx Tech Test Verification Core, we directly assessed more than 30 technologies that ultimately contributed to an increase of the country's total testing capacity by 1.7 billion tests to date. In this review, we present central lessons learned from this "apples-to-apples" comparison of novel, rapidly developed diagnostic devices. Overall, the evaluation framework and lessons learned presented in this review may serve as a blueprint for engineers developing point-of-care diagnostics, leaving us better prepared to respond to the next global public health crisis rapidly and effectively.

The impact of language barriers & interpreters on critical care patient outcomes.

BACKGROUND: In a multicultural society, the impact of language proficiency and interpreter use on critical care patient outcomes is unknown. OBJECTIVE: To investigate the relationship between English language preference, requirement for an interpreter and in-hospital mortality amongst non-elective intensive care unit (ICU) patients. METHOD: Adult patients admitted to all 23 public ICUs within the state of Victoria, Australia from July 2007 to June 2018, were extracted from The Australian New Zealand Intensive Care Society Adult Patient Database. De-identified patient data was matched using probabilistic methods and statistical linkage keys to the Victorian Admitted Episodes Database. Patients were classified into one of three groups: 'English preferred', 'English not preferred' and 'Interpreter required'. RESULTS: 126,891 ICU admissions were analysed, of whom 3394 (3%) were in the 'English not preferred' group and 6355 (5%) in the 'Interpreter required' group. Compared to the 'English preferred', both the 'English not preferred' and 'Interpreter required' groups were older, had more co-morbidities and higher severity of illness scores. In-hospital mortality was 13.1% in the 'English preferred' group, 19.6% in the 'English not preferred' group and 16.7% in the 'Interpreter required' group. However, after adjusting for sex, severity of illness and socio-economic status, the 'English not preferred' group remained with a higher risk adjusted mortality (OR 1.21, 95%CI 1.07-1.36, P = 0.002), whereas the 'Interpreter required' group had a lower adjusted risk of mortality (OR 0.81, 95%CI 0.74-0.89, P < 0.001). CONCLUSION: Being identified as having a requirement for an interpreter was associated with improved outcomes for adults admitted to public hospital ICUs in Victoria. Interpreter services should be more readily available in the hospital setting. It is recommended that patients, family members and clinicians actively use interpreter services when English is not the preferred language of an ICU patient.

Preoperative botulinum toxin A (BTA) injection versus component separation techniques (CST) in complex abdominal wall reconstruction (AWR): A propensity-scored matched study.

BACKGROUND: Complete fascial closure significantly reduces recurrence rates and wound complications in abdominal wall reconstruction. While component separation techniques have clear effectiveness in closing large abdominal wall defects, preoperative botulinum toxin A has emerged as an adjunct to aid in fascial closure. Few data exist comparing preoperative botulinum toxin A to component separation techniques, and the aim was to do so in a matched study. METHODS: A prospective, single-center, hernia-specific database was queried, and a 3:1 propensity-matched study of patients undergoing open abdominal wall reconstruction from 2016 to 2021 with botulinum toxin A versus component separation techniques was performed based on body mass index, defect width, hernia volume, and Centers for Disease Control and Prevention wound classification. Demographics, operative characteristics, and outcomes were evaluated. RESULTS: Matched patients included 105 component separation techniques and 35 botulinum toxin A. There was no difference in tobacco use, diabetes, or body mass index (all P > .5). Hernia defects and volume were large for both the component separation techniques and botulinum toxin A groups (mean size: component separation techniques 286.2 ± 179.9 cm2 vs botulinum toxin A 289.7 ± 162.4 cm2; P = .73) (mean volume: 1,498.3 + 2,043.4 cm3 vs 2,914.7 + 6,539.4 cm3; P = .35). Centers for Disease Control and Prevention wound classifications were equivalent (CDC3 and 4%-39.1% vs 40.0%; P = .97). Component separation techniques were more frequently performed in European Hernia Society M1 hernias (21% vs 2.9%; P = .01). The botulinum toxin A group had fewer surgical site occurrences (32.4% vs 11.4%; P = .02) and surgical site infections (11.7% vs 0%; P = .04). In multivariate analysis, botulinum toxin A was associated with lower rates of surgical site occurrences (odds ratio = 5.3; 95% confidence interval [1.4-34.4]). There was no difference in fascial closure (90.5% vs 100%; P = .11) or recurrence (12.4% vs 2.9%; P = .10) with follow-up (22.8 + 29.7 vs 9.8 + 12.7 months; P = .13). CONCLUSION: In a matched study comparing patients with botulinum toxin A versus component separation techniques, there was no difference in fascial closure rates or in hernia recurrence between the 2 groups. Preoperative botulinum toxin A can achieve similar outcomes as component separation techniques, while decreasing the frequency of surgical site occurrences.

Hernia recurrence after primary repair of small umbilical hernia defects.

BACKGROUND: An evidence-based approach to the repair of umbilical hernias (UH)<1 cm has yet to be defined. METHODS: A prospectively maintained, institutional hernia database was queried for patients undergoing primary suture repair of UH ≤ 1 cm. The primary outcome was recurrence and secondary outcomes were wound complications. RESULTS: Of 332 patients included (226-primary, 106-incisional), recurrence was identified in 4 (1.8%) primary versus 8 (7.5%) incisional-UH (p = 0.022), with follow-up of 4.7 ± 4.4 years. There were 10 (3.0%) wound complications: 4 (1.2%) superficial wound infections, 1 (0.3%) superficial wound dehiscence, and 5 (1.5%) seromas. On multivariable analysis of recurrence, incisional-UH had an odds ratio of 4.2 compared to primary. Suture choice, diabetes, BMI, tobacco-use history, and wound complications were not significant. CONCLUSIONS: With long term follow-up, recurrence after primary suture repair of UH ≤ 1 cm occurred in 1.8% of primary and 7.5% of incisional UH. On multivariable analysis, incisional-UH increased recurrence odds by 4.2 times compared to primary.

Don't forget about human factors: Lessons learned from COVID-19 point-of-care testing.

During the COVID-19 pandemic, the development of point-of-care (POC) diagnostic testing accelerated in an unparalleled fashion. As a result, there has been an increased need for accurate, robust, and easy-to-use POC testing in a variety of non-traditional settings (i.e., pharmacies, drive-thru sites, schools). While stakeholders often express the desire for POC technologies that are "as simple as digital pregnancy tests," there is little discussion of what this means in regards to device design, development, and assessment. The design of POC technologies and systems should take into account the capabilities and limitations of the users and their environments. Such "human factors" are important tenets that can help technology developers create POC technologies that are effective for end-users in a multitude of settings. Here, we review the core principles of human factors and discuss lessons learned during the evaluation process of SARS-CoV-2 POC testing.

Designing for simplicity: lessons from Mesa Biotech for microfluidic entrepreneurs and early-stage companies.

The COVID-19 pandemic has proven the need for point-of-care diagnosis of respiratory diseases and microfluidic technology has risen to the occasion. Mesa Biotech (San Diego, CA) originally developed the Accula platform for the diagnosis of influenza A and B and then extended the platform to SARS-CoV-2. Mesa Biotech has experienced tremendous success, culminating in acquisition by Thermo Fisher for up to $550m USD. The Accula microfluidics platform accomplished the leap from the lab to commercial product through clever design and engineering choices. Through information obtained from interviews with key Mesa Biotech leaders and publicly-available documents, we describe the keys to Mesa's success and how they might inform other lab-on-a-chip companies.

Multicenter analysis of laparoscopic versus open umbilical hernia repair with mesh: outcomes and quality of life (QoL).

INTRODUCTION: Umbilical hernia repair (UHR) is a common operation with varying surgical approaches. Laparoscopic (LUHR) and open (OUHR) operations are routinely performed, but their impact on quality of life (QoL) is not well described. Our aim was to evaluate perioperative outcomes and QoL of LUHR versus OUHR. METHODS: The prospectively collected International Hernia Mesh Registry was queried for patients undergoing UHR with mesh placement. QoL was measured using the Carolinas Comfort Scale preoperatively and 1, 6, 12, and 24 months postoperatively. Propensity match was performed controlling for hernia defect size (HDS), recurrent hernias, and BMI. RESULTS: 585 patients underwent 178 (30.4%) LUHR and 407 (69.6%) OUHR. LUHR patients had higher BMI, larger HDS, and more recurrent hernias (p < 0.05). Rates of other comorbidities were similar (p > 0.05). Tacks were used more frequently in LUHR (91.6% vs 1.7%, p < 0.001), and suture was used more often in OUHR (97.1% vs 47.8%, p < 0.001). Postoperative outcomes were similar (p > 0.05) except LUHR had higher rates of seroma (13.9% vs 4.3%, p < 0.001). Overall recurrence rates trended to favor OUHR, but not significantly (4.7% vs 8.4%, p = 0.07). The propensity match yielded 138 matched pairs. LUHR had more seromas and OUHR had higher infection rates (p < 0.05). Hernia recurrence was higher following LUHR (9.4% vs 2.9%, p = 0.02). QoL data were available for an average of 457 patients at each time period. QoL was superior in the OUHR group for pain and overall QoL at each time point and activity limitations at 6 and 12 months (p < 0.05). When examining patients who were asymptomatic preoperatively, OUHR had improved one-month overall QoL, but both groups had over 90% of patients report being asymptomatic postoperatively. CONCLUSIONS: OUHR is associated with higher rates of surgical site infections, but significantly lower rates of seroma formation and hernia recurrence compared to LUHR, while having superior QoL in both short- and long-term follow-up. Asymptomatic patients tend to have excellent QoL outcomes.

Structure of shear-induced platelet aggregated clot formed in an in vitro arterial thrombosis model.

The structure of occlusive arterial thrombi is described herein. Macroscopic thrombi were made from whole blood in a collagen-coated, large-scale stenosis model with high shear flow similar to an atherosclerotic artery. The millimeter-sized thrombi were harvested for histology and scanning electron microscopy. Histological images showed 3 distinctive structures of the thrombus. (1) The upstream region showed string-like platelet aggregates growing out from the wall that protrude into the central lumen, with red blood cells trapped between the strings. The strings were >10 times as long as they were wide and reached out to join the strings from the opposite wall. (2) Near the apex, the platelet strings coalesced into a dense mass with microchannels that effectively occluded the lumen. (3) In the expansion region, the thrombus ended abruptly with an annulus of free blood in the flow-separation zone. Scanning electron microscopy showed dense clusters of spherical platelets upstream and downstream, with amorphous platelets in the occluded throat consistent with prior activation. The total clot is estimated to contain 1.23 billion platelets with pores 10 to 100 µm in diameter. The results revealed a complex structure of arterial thrombi that grow from their tips under high shear stress to bridge the 2.5-mm lumen quickly with von Willebrand factor platelet strings. The occlusion leaves many microchannels that allow for some flow through the bulk of the thrombus. This architecture can create occlusion or hemostasis rapidly with minimal material, yet can remain porous for potential delivery of lytic agents to the core of the thrombus.

SIPA in 10 milliseconds: VWF tentacles agglomerate and capture platelets under high shear.

Shear-induced platelet aggregation (SIPA) occurs under elevated shear rates (10 000 s-1) found in stenotic coronary and carotid arteries. The pathologically high shear environment can lead to occlusive thrombosis by SIPA from the interaction of nonactivated platelets and von Willebrand factor (VWF) via glycoprotein Ib-A1 binding. This process under high shear rates is difficult to visualize experimentally with concurrent molecular- and cellular-resolutions. To understand this fast bonding, we employ a validated multiscale in silico model incorporating measured molecular kinetics and a thrombosis-on-a-chip device to delineate the flow-mediated biophysics of VWF and platelets assembly into mural microthrombi. We show that SIPA begins with VWF elongation, followed by agglomeration of platelets in the flow by soluble VWF entanglement before mural capture of the agglomerate by immobilized VWF. The entire SIPA process occurs on the order of 10 milliseconds with the agglomerate traveling a lag distance of a few hundred microns before capture, matching in vitro results. Increasing soluble VWF concentration by ∼20 times in silico leads to a ∼2 to 3 times increase in SIPA rates, matching the increase in occlusion rates found in vitro. The morphology of mural aggregates is primarily controlled by VWF molecular weight (length), where normal-length VWF leads to cluster or elongated aggregates and ultra-long VWF leads to loose aggregates seen by others' experiments. Finally, we present phase diagrams of SIPA, which provides biomechanistic rationales for a variety of thrombotic and hemostatic events in terms of platelet agglomeration and capture.

Thrombogenicity of biomaterials depends on hemodynamic shear rate.

BACKGROUND: While it is well recognized that different biomaterials induce thrombosis at low shear rates, the effect of high shear rates may be quite different. We hypothesize that the amount of thrombus formation on a given material can be greatly influenced by the local shear rate. METHODS: We tested this hypothesis with two different whole blood perfusion loop assays to quantify biomaterial thrombogenicity as a function of shear stress. One assay uses obstructive posts (pins) of material positioned centrally in a tube perfused at high shear rate of >5000/s for 24 h. A second assay uses a parallel plate chamber to perfuse low (<150/s), medium (~500/s), and high shear rates over 96 h. We evaluated the thrombogenicity of seven different biomaterials including stainless steel, acrylic, ceramic, Dacron, polytetrafluoroethylene (PTFE), silicone, and polyvinyl chloride (PVC). RESULTS: For the pin assay, thrombus mass was significantly greater for stainless steel than either zirconia ceramic or acrylic (p < 0.001). Similarly, the parallel plate chamber at high shear showed that steel and PTFE (p < 0.02) occluded the chamber faster than acrylic. In contrast, a low shear parallel plate chamber revealed that stainless steel and PTFE were least thrombogenic, while silicone, Dacron, and other plastics such as acrylic were most thrombogenic. Histology revealed that high shear thrombi had a large proportion of platelets not seen in the low shear fibrin-rich thrombi. CONCLUSION: This differential thrombogenicity based on shear rate conditions may be important in the selection of biomaterials for blood-contacting devices.

Global Thrombosis Test: Occlusion by Coagulation or SIPA?

The global thrombosis test (GTT) is a point of care device that tests thrombotic and thrombolytic status. The device exposes whole blood flow to a combination of both high and low shear stress past and between ball bearings potentially causing thrombin and fibrin formation. The question arises as to whether thrombosis in the GTT is dominated by coagulation-triggered red clot or high shear-induced white clot. We investigated the nature of the thrombus formed in the GTT, the device efficacy, human factors use, and limitations. The GTT formed clots that were histologically fibrin-rich with trapped red blood cells. The occlusion time (OT) was more consistent with coagulation than high shear white clot and was strongly lengthened by heparin and citrate, two common anticoagulants. The clot was lysed by tissue plasminogen activator (tPA), also consistent with a fibrin-rich red clot. Changing the bead to a collagen-coated surface and eliminating the low shear zone between the beads induced a rapid OT consistent with a platelet-rich thrombus that was relatively resistant to heparin or tPA. The evidence points to the GTT as occluding primarily due to fibrin-rich red clot from coagulation rather than high shear platelet aggregation and occlusion associated with arterial thrombosis.

The RADx Tech Test Verification Core and the ACME POCT in the Evaluation of COVID-19 Testing Devices: A Model for Progress and Change.

Faced with the COVID-19 pandemic, the US system for developing and testing technologies was challenged in unparalleled ways. This article describes the multi-institutional, transdisciplinary team of the "RADxSM Tech Test Verification Core" and its role in expediting evaluations of COVID-19 testing devices. Expertise related to aspects of diagnostic testing was coordinated to evaluate testing devices with the goal of significantly expanding the ability to mass screen Americans to preserve lives and facilitate the safe return to work and school. Focal points included: laboratory and clinical device evaluation of the limit of viral detection, sensitivity, and specificity of devices in controlled and community settings; regulatory expertise to provide focused attention to barriers to device approval and distribution; usability testing from the perspective of patients and those using the tests to identify and overcome device limitations, and engineering assessment to evaluate robustness of design including human factors, manufacturability, and scalability.

Negatively charged nanoparticles of multiple materials inhibit shear-induced platelet accumulation.

Platelet accumulation by VWF under high shear rates at the site of atherosclerotic plaque rupture leads to myocardial infarction and stroke. Current anti-platelet therapies remain ineffective for a large percentage of the population, while presenting significant risks for bleeding. We explore a novel way to inhibit arterial thrombus formation. Theoretically, a negative charge may influence the tertiary structure of VWF to favor the globular configuration by biophysical means without the use of platelet inactivating drugs. We tested this hypothesis experimentally for charged nanoparticles (CNPs) to inhibit thrombus formation in a microfluidic thrombosis assay (MTA). Several different CNPs demonstrated the ability to retard thrombotic occlusion in the MTA. A preliminary study in mice shows that thrombus stability is weaker with CNP administration and bleeding times are not markedly prolonged. The CNPs tested here show promise as a new class of antithrombotic therapies that act by biophysical means rather than biochemical pathways.