Procalcitonin (PCT) can discriminate bacterial from viral systemic infections and true bacteremia from contaminated blood cultures. The aim of this study was to evaluate PCT diagnostic accuracy in discriminating Gram-positive, Gram-negative, and fungal bloodstream infections. A total of 1,949 samples from patients with suspected bloodstream infections were included in the study. Median PCT value in Gram-negative (13.8 ng/mL, interquartile range (IQR) 3.4–44.1) bacteremias was significantly higher than in Gram-positive (2.1 ng/mL, IQR 0.6–7.6) or fungal (0.5 ng/mL, IQR 0.4–1) infections (P < 0.0001). Receiver operating characteristic analysis showed an area under the curve (AUC) for PCT of 0.765 (95% CI 0.725–0.805, P < 0.0001) in discriminating Gram-negatives from Gram-positives at the best cut-off value of 10.8 ng/mL and an AUC of 0.944 (95% CI 0.919–0.969, P < 0.0001) in discriminating Gram-negatives from fungi at the best cut-off of 1.6 ng/mL. Additional results showed a significant difference in median PCT values between Enterobacteriaceae and nonfermentative Gram-negative bacteria (17.1 ng/mL, IQR 5.9–48.5 versus 3.5 ng/mL, IQR 0.8–21.5; P < 0.0001). This study suggests that PCT may be of value to distinguish Gram-negative from Gram-positive and fungal bloodstream infections. Nevertheless, its utility to predict different microorganisms needs to be assessed in further studies.

Early diagnosis and prompt targeted therapy are essential for septic patients' outcome. Procalcitonin (PCT) has been shown to predict bacteraemia and bacterial DNAaemia. Presepsin, the circulating soluble form of CD14 subtype, increases in response to bacterial infections, and is considered a new, emerging, early marker for sepsis. We evaluated the diagnostic accuracy of presepsin in predicting bacteraemia and bacterial DNAaemia in 92 patients with suspected sepsis, and we compared it with that of PCT and C-reactive protein (CRP). Presepsin median values were significantly higher in bacteraemic vs non-bacteraemic patients [1290 pg ml .07, respectively). Both biomarkers performed significantly better than CRP, which had an AUC for bacteraemia of 0.602 and for DNAaemia of 0.632 (all P values <0.05). In conclusion, in patients with suspected sepsis, presepsin and PCT showed a good diagnostic accuracy in predicting both bacteraemia and bacterial DNAaemia, superior to CRP. INTRODUCTIONSepsis, a systemic deleterious host response to infection that leads to organ dysfunction (Dellinger et al., 2013), is a major cause of morbidity and mortality (Mayr et al., 2014). Early diagnosis and prompt targeted therapy are essential for patients' outcome (Kumar et al., 2006).Blood culture (BC) is the gold standard for pathogen detection, although false-negative results, especially in antibiotic pre-treated patients, can occur (Opota et al., 2015). New approaches to speed sepsis diagnosis include molecular assays and the use of specific biomarkers (Reinhart et al., 2012). Molecular technologies, allowing a rapid detection of microbial DNA, could represent an important additional tool for the aetiological diagnosis of bloodstream infections, particularly in antibiotic pre-treated patients (Dark et al., 2015;Mongelli et al., 2015;Pasqualini et al., 2012). Indeed, real-time PCR (RT-PCR) can detect not only viable microorganisms in patient's blood (bacteraemia) but also circulating bacterial DNA (DNAaemia) that persists for several days in blood during antimicrobial treatment or may be released into the bloodstream from the primary infectious foci (Øvstebø et al., 2004;Navarro et al., 2006;Peters et al., 2007).During recent years, many biomarkers have been evaluated and compared to find the best predictor of sepsis (Cho & Choi, 2014). Procalcitonin (PCT) has been identified as having a good diagnostic accuracy for predicting bacteraemia and pathogen DNAaemia in different clinical settings (Koivula et al., 2011;Mencacci et al., 2012), representing an advance over C-reactive protein (CRP) (Barati et al., 2008;Leli et al., 2014;Yu et al., 2010 Rabensteiner et al., 2014;Romualdo et al., 2014;Shozushima et al., 2011).To the best of our knowledge, no study described presepsin diagnostic accuracy in predicting both bacteraemia and bacterial DNAaemia, which was the first aim of this study.The second aim was to compare the diagnostic accuracy of presepsin with that of PCT and CRP. METHODSPatients and samples. This prospective observational stud...

PCT showed a better diagnostic accuracy than CRP, ESR, and WBC count in predicting DNAemia and bacteremia in patients with suspected sepsis.

Background: Long-term outcomes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are now recognized as an emerging public health challenge - a condition termed Long-COVID. The pathophysiology of Long-COVID remains to be established. Functional P-selectin activity, implicated in COVID-19 sequalae, was measured between two convalescent COVID-19 subjects, one with (Long-COVID subject) and another without Long-COVID symptoms. Methods: Flow adhesion of whole blood or isolated white blood cells to P-selectin (FA-WB-Psel and FA-WBC-Psel) was measured using a standardized microfluidics clinical assay; impedance aggregometry with a collagen agonist was measured using model 590 Chrono-Log impedance aggregometer; standard laboratory assays were performed to evaluate changes in blood chemistries. Results: For both subjects, hemoglobin, WBC, platelet counts, electrolytes and ferritin were within normal reference ranges, with FA-WB-Psel significantly elevated compared to healthy controls (p<0.01). In vitro treatment of whole blood samples with crizanlizumab (anti-p-selectin monoclonal antibody) within the clinical dose range (10 μg/ml) mL) inhibited FA-WB-Psel only in samples from asymptomatic post-COVID subject, with the Long-COVID subject sample requiring close to 5-fold elevated dose to achieve a response. Pronounced inhibition of P-selectin adhesion of isolated leukocytes was observed for both subjects in autologous platelet-poor plasma and buffer. Impedance aggregometry showed greater baseline platelet aggregation to collagen in the Long-COVID sample, although both samples responded similarly to aspirin-induced platelet inhibition. Conclusions: Presented results suggest that elevated platelet activation in Long-COVID subject may be associated with increased P-Selectin activity. The results are discussed in terms of possible use on P-selectin inhibition therapies in treating Long-COVID.

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause severe vascular complications associated with endothelial dysfunction and systemic inflammation. COVID19-specific IgG are detectable within a week of infection. Long COVID-19 has been described in patients continuing to exhibit symptoms after the virus is no longer detectable in the respiratory secretions, including fatigue, dyspnea, headache, and brain fog. The recent FAIR Health study reviewed a total of 1,959,982 COVID-19 patients for the prevalence of long COVID symptoms and reported that 23.2% had at least one post-COVID symptom [1]. The underlying biologic mechanisms of long COVID remain unclear, thus treatments are limited to symptomatic relief and supportive care. Many long COVID symptoms are consistent with systemic inflammation and impaired oxygen delivery observed in individuals with sickle cell disease (SCD), in turn associated with elevated blood cell adhesion and decreased red blood cell (RBC) stability. The aim of this study was to determine if deleterious changes in in blood cell properties related to adhesion and membrane stability under stress can be associated with the symptoms of long COVID-19. In this work we evaluated 7 SCD patients that were diagnosed with SARS-Cov-2 and tracked their recovery using semiquantitative IgG and blood cell function assays. Methods: Blood samples were collected by the Foundation for Sickle Cell Disease (SCD) Research from SCD (homozygous SS, n=6) patients coming for regular or urgent clinic visit with SARS-CoV-2 serological and blood cell functions tests performed per the standard of care. Semiquantitative IgG assay was performed using DXi-80 (Beckman Coulter). Flow adhesion of whole blood to VCAM-1 (FA-WB-VCAM)and P-Selectin (FA-WB-Psel) substrates were determined by counting the cells that remain adherent in a microfluidics channel after perfusion with whole blood 1:1 diluted with HBSS buffer and washed by reversed flow at 1 dyne/cm 2. Red blood cell mechanical fragility (RBC MF) was measured as hemolysis induced by an oscillating cylindrical magnet with periodic non-invasive probing of cell-free hemoglobin fraction. Six individuals with SCD recovering from SARS-Cov-2 with biomarker data available both before and for more than 3 months after the infection (179±62 days) were included in the study. Results: IgG levels varied from less than 0.1 to 37, with positive values being defined as IgG &gt; 1. The median estimated half-life of IgG decline was 53 days ranging from 25 to 90 days (the last, for the hospitalized patient). Averaged for IgG positive (IgG+) and IgG negative (IgG-) conditions, combining pre- and post-infection IgG- conditions, values of patient hemoglobin (Hb), FA-WB-VCAM, FA-WB-Psel, and RBC MF cell properties lacked statistical significance (under both a paired t-test and population statistics). Hb levels remained essentially unchanged regardless of the time from infection or IgG status. However, FA-WB-VCAM, FA-WB-Psel, and RBC MF were all significantly elevated after SARS-Cov-2 seroconversion and remained elevated despite declining IgG levels (e.g., Fig. 1). These increases in biomarker values were statistically significant for both FA-WB-VCAM and RBC MF, and were approaching significance for FA-WB-Psel (p&lt;0065). These increases were highly patient-specific with potential return to pe-infection values observed in some cases at about 5-6 months after the infection. A qualitative review of the medical records indicated a new subjective report of fatigue in 5 of 6 patients. Longer observations are required to determine if abnormal blood cell adhesive properties and RBC membrane instability are mechanisms of long-COVID-19 pathophysiology. Conclusions: Whole blood adhesion to both p-selectin and VCAM-1 as well as RBC membrane stability can be significantly impaired in convalescent SARS-Cov-2 patients suggesting an association with long COVID-19. New and emerging treatments that modify whole blood adhesive properties and RBC membrane stability should be investigated for their potential to accelerated recovery from long COVID-19. Health F. A Detailed Study of Patients with Long-Haul COVID: An Analysis of Private Healthcare Claims; White Paper. June 15, 2021 Disclosures Tarasev: Functional Fluidics: Current holder of stock options in a privately-held company. Ferranti: Functional Fluidics: Current holder of stock options in a privately-held company. Allen: Functional Fluidics: Current Employment. Gao: Functional Fluidics: Current Employment. Topping: Functional Fluidics: Current Employment. Ferranti: Functional Fluidics: Current Employment. Makinde-Odesola: Functional Fluidics: Other: conduct research for academic program. Hines: Functional Fluidics: Current holder of stock options in a privately-held company.

Sickle cell disease (SCD) is characterized by frequent and unpredictable vaso-occlusive crises (VOCs) resulting in increased morbidity and mortality. Reliable biomarkers that predict the onset and progression of VOCs in SCD are unavailable, thus the existing standard of care is more focused on VOC intervention as opposed to VOC prevention. Sickle blood cells contribute to VOCs by adhering to the endothelium and aggregating to other blood cells in the circulation through pathologic adhesive interactions. In our previously described ELIPSIS study, blood samples were collected from 35 study subjects with SCD every 3 weeks during self-reported baseline and during self-reported VOCs (at home or in a healthcare setting). An electronic, patient-reported outcomes (ePRO) tool captured daily pain, VOC, and VOC resolution. Flow adhesion of whole blood to VCAM-1 (FA-WB-VCAM) and P-selectin (FA-WB-Psel) were assessed during each visit. Time-To-Resolution was established as the duration between the onset and subject self-reported resolution of VOC resolution and varied between 2 and 48 days. For the subset of TTR limited to ≤ 7 day, TTR was negatively correlated with FA-WB-PSel measured at the onset of VOC (R2=0.45; r=-0.67;p<0.05). Coefficient of determination increased to 0.62 when baseline FA-WB-VCAM levels were used as a second predictor in the multi-parametric model. In such a model, baseline FA-WB-VCAM was positively correlated with TTR at ≤ 7 day, with the difference in the sign of P-selectin and VCAM-1 effect on the reduction of pain (TTR duration) likely reflecting different mechanisms driving VOCs. Supplementation of FA-WB-VCAM and FA-WB-Psel multiparametric model with select blood chemistry biomarkers including several inflammatory mediators, further enhanced models ability to predict TTR. This study indicates that functional biomarkers obtained both at baseline and at the time of VOC can give insight into the time it may take for that specific VOC to resolve. These could assist providers in predicting which VOCs may require more intensive intervention. These data may also identify specific VOC phenotypes, allowing providers to intervene with a more patient-specific approach. Future studies are required to determine if FA-WB-VCAM and FA-WB-Psel can be used clinically to enable a more precision medicine-based approach to manage VOCs and if such an approach could result in improved outcomes and reduced healthcare costs by predicting VOCs for early intervention.

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Background: Long-term outcomes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are now recognized as an emerging public health challenge - a condition termed post-acute coronavirus 2019 syndrome (PACS) or Long-COVID. The pathophysiology of Long-COVID remains to be established, several mechanisms in study focus on the role of P-selectin, an inflammation-induced protein expressed by platelets and endothelial cells. Functional P-selectin activity, potentially implicated in COVID-19 and Long-COVID sequelae, was measured for a Long-COVID subject at 68 weeks from the SARS-CoV-2 infection after fully recover from the syndrome. It was compared with the results from the same subject at 20 weeks post-infection, when subject experienced severe Long-COVID symptoms. Methods: Flow adhesion of whole blood or isolated white blood cells to P-selectin (FA-WB-Psel and FA-WBC-Psel) was measured using a standardized microfluidics clinical assay; impedance aggregometry with a collagen agonist was measured using model 590 Chrono-Log impedance aggregometer; standard laboratory assays were performed to evaluate changes in blood chemistries. Results: After recovery from Long-COVID, RBC count and D-dimer remained elevated and other blood chemistry results remained within the normal range as compared to 20 weeks post infection when severe Long-COVID symptoms were present. Total iron and transferrin-iron saturation percentage values that were elevated when symptoms were present, declined to normal range. Whole blood aggregometry results indicate an absence of previously present platelet hyperactivity. FA-WB-PSel that was significantly elevated during Long-COVID (590 +/- 260 cells/mm2) was significantly reduced after the resolution of Long-COVID symptoms (98 +/- 38 cells/mm2). However, supplementation of whole blood with crizanlizumab did not result in any measurable inhibition of cell adhesion to P-selectin, similarly with previously reported. Similar to what was observed for the subject when Long-COVID symptoms were present, crizanlizumab, even at a dose 10-fold lower than clinical, induced pronounced inhibition of FA-WBC-Psel when tested in buffer, but not in patient own plasma. Conclusions: This report documents the changes in leukocyte adhesion properties for a patient at more than a year from the initial infection after the gradual resolution of Long-COVID symptoms, as compared to when Long-COVID symptoms were present. Recovery from Long-COVID may be associated with normalization of platelet activity, but not necessarily with complete alleviation of endothelial activation. It remains to be determined to what extent changes in leukocyte adhesion to P-selectin may represent a new risk factor for a mechanism driving Long-COVID syndrome.