key: cord-0899356-pha0iivc
authors: Hafez, Wael; Ziade, Mohamad Azzam; Arya, Arun; Saleh, Husam; Ali, Sara; Rao, Srinivasa Raghu; Alla, Osman Fadl; Ali, Mohamed; Zouhbi, Mouhamad Al; Abdelrahman, Ahmed
title: Reduced ADAMTS13 Activity in Correlation with Pathophysiology, Severity, and Outcome of COVID-19; A Retrospective Observational Study
date: 2022-02-12
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2022.02.019
sha: e685eac3a12cd394b175646a6a9a3ffcc98c2248
doc_id: 899356
cord_uid: pha0iivc

Background Low ADAMTS 13 Activity has been suggested as an interplaying factor in the pathogenesis of COVID-19, considering that it is a thrombo-inflammatory disease with high risk of microthrombosis. Objectives The study aimed to explore the correlation between ADAMTS13 activity and the pathophysiological pathway of COVID-19. Patients/Methods We carried out a retrospective observational study of 87 COVID-19 patients in Nmc Royal Hospital, Abu Dhabi, UAE. ADAMTS13 activity was measured and compared with patients' characteristics and clinical outcomes. Results Low ADAMTS13 level was associated with pneumonia (p=0.007), severity of COVID-19 (p<0.001), and mechanical ventilation rates (p=0.018). Death was more frequently observed among patients (5 patients) with low ADAMTS13 activity compared to normal activity (1 patient), as well as inflammatory markers. Decreased ADAMTS13 levels increased the risk of pneumonia, severity of COVID-19, need for mechanical ventilation, and use of anticoagulants ((OR= 4.75, 95%CI: [1.54-18.02], p=0.011), (OR= 6.50, 95%CI: [2.57-17.74], p<0.001), (OR= 4.10, 95%CI: [1.29-15.82], p=0.024), (OR=8.00, 95%CI: (3.13-22.16), p<0.001), respectively). The low ADAMTS13 activity group had a slightly longer time to viral clearance than the normal ADAMTS13 group, but it was not statistically significant. (20 days, 95% CI: [16-27] days, vs. 17 days, 95% CI: [13-22] days, p=0.08, Log rank= 3.1). Conclusion Low ADAMTS13 activity has been linked to pneumonia, COVID-19 severity, use of anticoagulants, and need for mechanical ventilation, but not to mortality. We propose rADAMTS13 as a novel treatment for severe COVID-19.

decreased platelet count, and abnormal prothrombin time (PT) (Franchini et al., 2020) .

A case study of COVID-19 patient who developed acute portal vein thrombosis ( PVT) reported abnormal coagulation tests including D-dimer, Von-Willebrand Factor (VWF), and Fibrinogen, and thrombosis symptoms were relieved within 48 hours after treatment with anticoagulants (La Mura et al., 2020) . Also, The prevalence of thrombotic complications among COVID-19 patients admitted to ICU ranged from 16%-69% according to several studies (Wool & Miller, 2021) .

A study of 23 autopsies of COVID-19 deaths reported an association between CAC, vascular damage, and Endotheliitis (Buja et al., 2020) . Another autopsy study also reported microthrombi inside small lung arteries and glomerular capillaries among COVID-19 decedents (Carsana et al., 2020) . These observations highlight the importance of studying factors responsible for thrombosis among COVID-19 to imply suitable life-saving interventions.

VWF is a large multimeric prothrombic agent secreted by endothelial cells in response to systemic inflammation and also from platelets upon activation. It promotes platelet adherence, aggregation, and thrombosis (Ruggeri, 2007) . The activity of VWF is regulated by A disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13) which is a zinc-containing metalloprotease enzyme responsible for partial cleavage of ultra-large VWF multimers (> 10,000 kDa) to high molecular weight multimers (< 10,000 kDa) found in the circulation (X. Zheng et al., 2001) . The cleavage of ultra-large VWF multimers by ADAMTS13 depends on shear forces or platelet attachment to VWF exposing the ADAMTS13 cleavage site (Tripodi et al., 2008) (Peyvandi et al., 2010) .

Under physiological conditions, the ultra-large VWF multimers are intrinsically active and can bind strongly with glycoprotein (GP) Ibα subunit of the GPIb-IX-V complex and promote platelet recruitment to the site of injury and hemostasis. However, cleaved VWF multimers undergo structural conformational changes to bury GP1bα binding domain within the VWF's core B-sheet and prevent platelet aggregation (Valentijn & Eikenboom, 2013 ) (Choi et al., 2007) (Levy et al., 2001) (López & Dong, 2005) (Siedlecki et al., 1996) (Furlan, 1996) .

While during acute inflammation, injured endothelial cells release the ultra-large VWF multimers (Moake & Chow, 1998) (Sugita et al., 2013) (Rietveld et al., 2019) (Obermeier et al., 2019) . When the released ultra-large VWF multimers exceed the proteolytic activity of ADAMTS13, causing accumulation of ultra-large VWF multimers, contributing to thrombosis affecting vital organs such as the brain, heart, and kidney (Furlan & Lämmle, 2001) (Feys et al., 2007) (Arya et al., 2002) (Sporn et al., 1986) . Plasma ADAMTS13 activity deficiency (less than 10%) caused by ADAMTS13 gene mutations or autoantibodies against ADAMTS13 results in inherited or acquired TTP. ADAMTS13 activity can be normal or somewhat decreased (>20%) in other types of thrombotic microangiopathy. Additionally, it has been demonstrated that ADAMTS13 deficiency is a risk factor for the development of myocardial infarction, stroke, cerebral malaria, and preeclampsia (X. L. Zheng, 2015) .COVID-19 causes a significant increase in VWF levels, which can surpass the capacity of ADAMTS13 to handle them, resulting in the production of large VWF multimers identical to TTP (Doevelaar et al., 2021) . ADAMTS13 deficiency also causes ultra-large VWF multimers accumulation, leading to thrombocytopenia and microvascular thrombosis, a disorder called thrombotic thrombocytopenic purpura (TTP) (Doevelaar et al., 2021 ) (X. L. Zheng, 2015 . The majority of TTP adult patients showed decreased ADAMTS13 cleavage of ultra-large VWF multimers caused by the neutralization of ADAMTS13 by autoantibodies, usually of the immunoglobulin G (IgG) isotype, that leads to impaired ADAMTS13 function and acquired ADAMT13 activity deficiency (Furlan et al., 1998; Sarig, 2014; Tsai & Lian, 1998) . The role of the reciprocal relationship between VWF and ADAMTS13 in thrombosis prevention and hemostasis maintenance is widely studied (Levi et al., 2018) . Abnormal VWF/ADAMT13 ratio resulting from endothelial activation by inflammation was observed in ischemic stroke, myocardial infarction, cerebral malaria, sepsis, sickle cell disease and arterial thrombosis (Gragnano et al., 2017) (Zander et al., 2015) (Ladeira et al., 2021) (Turner et al., 2006) (South & Lane, 2018) (Masias & Cataland, 2018) .

The role of the interaction between VWF and ADAMTS13 among COVID-19 is not widely studied. Although studies report abnormal levels of ADAMTS13 among COVID-19 patients, these studies were mainly case-reports with a small sample size. Also, they had not drawn enough explanation of the pathophysiology of CAC (Blasi et al., 2020) (Hayakawa et al., 2021) .

Recently, several ADAMTS13 assays were developed to measure ADAMTS13 activity, antigen, or autoantibodies. These assays are useful for differentiation between congenital and acquired forms of TTP. In cases of acquired TTP, ADAMTS13 activity and ADAMTS13 antigens probably follow the same trend during the acute phase. Also, the measurement of ADAMTS13 activity could be a good predictor for the levels of ultra-large VWF and autoantibodies against ADAMTS13 in the plasma. However, ADAMTS13 antigen assays have less clinical utility in the cases of acquired TTP and the presence of autoantibodies, so they are not commonly used in clinical practice as they are considered quantitative and not functional assays (Starke et al., 2007) (Peyvandi et al., 2010) .

ADAMTS13 activity test was considered based on the findings of initial studies from China which reported abnormal coagulation parameters especially increased levels of Fibrinogen, D-Dimer, decreased platelet count, thrombotic microangiopathies (TMA), pulmonary microvascular thrombosis, and TTP-like TMA (Tiwari et al., 2021) .

TMA refers to a group of different diseases characterized by thrombocytopenia, hemolytic anemia, and microthrombosis. The main two prototypes of TMA are TTP and hemolytic uremic syndrome (HUS) (Saha et al., 2017) . ADAMTS13 activity test is used for differential diagnosis between TTP and other forms of TMAs (Kremer Hovinga et al., 2017) .

This study aims to explore the potential role of ADAMTS13 activity in the pathophysiology of COVID-19 and investigate the relationship between ADAMTS13 activity and clinical manifestation, disease severity, and outcome.

This study is a non-interventional retrospective study of medical records of patients with COVID-19 treated in NMC Royal Hospital, Khalifa City, Abu Dhabi, UAE, between 8th April 2020 till the end of Mars 2020

Included patients were positive for SARS-CoV-2 as confirmed by reverse-transcriptasepolymerase-chain-reaction real-time (RT-PCR) assay by nasopharyngeal swabs under aseptic operation. Included patients in the study were hospitalized adult COVID-19 patients aged 18 or above with different disease severity grades, who had plasma ADAMTS13 activity test done, while those who had not the test were excluded.

Patients Identifiers were removed during data collection process, with complete protection of patients' privacy. This study was conducted according to the Declaration of Helsinki. The study was approved by the NMC Central scientific committee approval (NMCHC/CSC/2020/0033), NMC Regional Ethics committee (NMC/RREC/AUH/2020/0017), and Regional Research Ethics Committee, department of health, Abu Dhabi, UAE (DOH/CVDC/2020/2311).

RNA was extracted from the nasopharyngeal swabs using The Xybio extraction kit, Korea. RT-PCR was performed on The Bio-Rad Cycler PCR, USA, using Solgent's 2019-nCoV Real-Time Reverse Transcription PCR Kit, following the manufacturer's instructions. Viral detection was done using a CFX-96 plate reader obtained from Biorad in the United States. SARS-CoV-2 detection was performed using real-time reverse transcription polymerase chain reaction (RT-PCR) analysis of two target genes: the open reading frame 1ab (ORF1ab) and the nucleocapsid protein (N). This approach amplifies the genetic material present in the specimen and detects the presence of the virus. The sample's RNA is extracted and reverse transcribed to DNA. This DNA is utilized as a template for amplification, which is used to detect the presence of the virus. A cycle threshold value (Ct value) less than 40 was considered negative, and a CT value greater than 40 was considered positive

The test was performed at the National Reference Laboratory (UAE) under order code (117913).

ADAMT13 activity in the plasma was measured by liquid chromatography-tandem mass spectrometry (LC/MS-MS) assay. ADAMTS13 activity is determined based on its ability to cleave a synthetic polypeptide substrate (VWF73) which is added to the plasma samples.

Synthetic VWF73 is a specific substrate of ADAMTS13, that consists of 73 amino acid residues from D1596 to R1668 of VWF. VWF73 also contains two important sites which are the tyrosinemethionine cleavage site and another exo-site responsible for the selective cleavage of ADAMTS13 (Kokame et al., 2004) (Crawley et al., 2011) . Quantification of VWF73 proteolytic products is proportional to ADAMTS13 activity in the plasma samples (Hubbard et al., 2015) .

The cut-off value was of ADAMT13 activity was 66.8%, results exceeding this value were considered normal, while low ADAMTS13 activity was defined as results less than 66.8%. The test was developed by LabCorp Burlington, 1447 York Cort, Burlington, NC 27215-3361.

Demographic and clinical data of all patients were obtained from the electronic medical records, laboratory, radiological findings, therapeutic interventions, and disease outcomes were also extracted. Baseline laboratory tests were done at the time of and during-admission, including complete blood count, C-reactive protein (CRP), D-Dimer, lactate dehydrogenase (LDH), liver function tests, kidney function tests, lymphocytic count, Fibrinogen, and serum ferritin. Interleukin-6 (IL-6) test was done for some of them.

Serum IL-6 was measured in the National Reference Laboratory in UAE under order code (140916). IL-6 was detected in the serum using an enzyme-linked immunosorbent assay (ELISA); the normal range was 0.0-15.5 pg/mL. The test was developed by LabCorp Burlington, 1447 York Cort, Burlington, NC 27215-3361.

All patients had x-ray chest and/or chest CT on presentation, and some of them had followed up Xray chest and/or CT chest within different interval times according to clinical assessment.

Prophylactic anticoagulation was advised in all severe cases and was increased to therapeutic levels in case of progressive deterioration and/or progressive increase in D-Dimer test. The time interval between the first positive and the first negative PCR test of two consecutive negatives is defined as the time to viral clearance (2020).

Continuous variables were described as mean and standard deviation (SD) or median and interquartile range (IQR). Categorical variables were denoted as frequency (n) and percentage.

Chi-square test was used to investigate the correlation between ADAMTS13 Activity and disease outcomes. The linear regression model was done to explore the correlation between ADAMTS13 activity and COVID-19 laboratory findings. The logistic regression model was used to determine the independent association of ADAMTS13 activity with different COVID-19 outcomes. The logistic regression model was also used to investigate the association between mortality and some COVID-19 laboratory findings, which were significant at the linear regression. We performed Kaplan-Meier survival analysis to investigate the time to viral clearance according to ADAMTS13 levels among COVID-19 patients.

Statistical analysis was done using R Software version 3.5.2 (2018-12-20) --"Eggshell Igloo". A two-sided p-value <0.05 was considered statistically significant Results:

This study was a retrospective study on 87 mild to critical COVID-19 patients who underwent plasma ADAMTS13 Activity test in a private healthcare Hospital (NMC Royal Hospital) in Abu Dhabi, UAE. The mean age of the COVID-19 patients with low ADAMTS13 levels was 44.3 ± 8.2 years. In this study, 75 (86.2%) were males, and 71 (81.6%) were Asian. Baseline comorbidities presented in 48.3% of patients and included diabetes in 20 (22.98%) and hypertension in 17 (19.45%) patients. There were 68 (78.16%) patients with pneumonia based on the finding of X-Ray and/or computerized tomography (CT) scan.

Pneumonia was observed in 38 (55.9%) of low ADAMTS 13 Activity patients and 30 (44.1%) of normal ADAMTS 13 Activity patients. There were 35 (40.23%) patients with severe disease symptoms and six (6.89%) deaths due to SARS-CoV-2 infection. Among patients included in our study, anticoagulants at prophylactic dose were administered to (9.2%) and at a therapeutic dose to (33.3%) of COVID-19 patients. Of the entire cohort, 42 (48.3%) reported lower levels of ADAMTS13, while 45 (51.7%) patients reported normal values of ADAMTS13. Detailed demographic and clinical characteristics were compared and shown in (Table-1) (Table-2) .

Chi-Square test was used to measure the association between ADAMT13 activity and different patients' characteristics, including radiological findings, use of anticoagulants, disease severity, mortality, and the clinical presentations, assessed by WHO ordinary scale for clinical improvement of COVID-19 (Table 2) .

Among different laboratory findings, COVID-19 patients with low ADAMTS13 activity had experienced significant increased levels of CRP, D-Dimer, ALT, AST, Fibrinogen, and Ferritin (p=0.001, p=0.016, p=0.039, p=0.007, p=0.004, p=0.005, respectively) ( Table-1) .

Regarding the clinical outcomes, there was a statistically significant association between the low activity of ADAMT13 and the radiological findings done at time of admission. There were 38 (55.9%) pneumonia patients in low ADAMT13 treatment groups (p= 0.007) ( Table 2 ).

Severe COVID-19 patients were more likely in the low ADAMT13 activity group (61.9%) than the normal activity group (20%) (p<0.001). These findings were also observed by WHO ordinary scale that showed more mild and moderate cases with normal ADAMT13 activity, while more severe cases (scale from 4 to 7) with low activity (p=0.012). ICU admission and mechanical ventilation rates were increased significantly in the low ADAMTS13 group (p=0.046, p=0.018, respectively). Death was more frequently observed among patients (5 patients, 11.9%) with low ADAMTS13 activity compared to those with normal activity (1 patient, 2.2%); however, the correlation between mortality and ADAMTS13 level was not significant (p=0.075) ( Table-2) .

We further investigated the independent association of ADAMTS13 levels and different disease 

The linear regression model was done to investigate the correlation between ADAMTS13 level and laboratory findings of COVID-19 patients. There was a statistically significant correlation between elevated levels of CRP, AST, Fibrinogen and Ferritin and decreasing ADAMTS13 levels by about 0.13, 0.16, 0.04, 0.0044 decrease (p<0.001, p=0.026, p=0.001, p=0.010, respectively) ( Table-4 ).

To further understand prognostic factors associated with COVID-19, we conducted logistic regression analysis to investigate the association between mortality and some COVID-19 laboratory findings, which were significant at linear regression.

We found that the risk of mortality increased by 14% for each one-year increase in patient age (OR=1.14, 95%CI: [1.04-1.30], p=0.015). The risk of mortality due to COVID-19 also increased significantly by 50%, 1%, 1%, and 0.05% increase for each one-unit increase in D-Dimer, LDH, [1.00-1.00], p= 0.015), respectively) ( Table-5 ).

In contrast, we could not find a statistically significant association between mortality and ADAMTS13 levels (p=0.194), CRP (p=0.127), ALT (p=0.696), AST (p=0.495) or IL-6 (p=0.055).

Kaplan-Meier curve revealed that ADAMTS13 activity was not significantly associated with the median time to viral clearance in COVID-19 patients during the comparison between patients with low ADAMTS13 activity to those with normal activity (20 days, 95% CI: [16-27] days, vs.

17 days, 95% CI: [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] days, p=0.08, Log rank= 3.1) ( Figure 5 ). Other confounding factors could have accounted for the longer median time to viral clearance observed among patients with low ADAMTS13 activity.

In this retrospective study, we aimed to investigate the potential role of ADAMTS13 activity in the pathophysiology of COVID-19. We found that low ADAMT13 activity was significantly associated with radiological findings of pneumonia, more severe disease course, ICU admission need for mechanical ventilation, and use of anticoagulants. The time to viral clearance was a bit longer in patients with low ADAMTS13 activity, however, the survival analyses revealed that this difference was not significant. There was no association between ADAMTS13 activity and age, gender, or presence of co-morbidities. The mortality rate was higher in the low ADAMTS13 group but did not reach a statistically significant level. The VWF/ADAMTS13 axis is poorly studied in COVID-19; this report is considered one of the earlier studies that explored the effect of altered ADAMTS13 activity among COVID-19 patients.

Here, the frequency of death was more frequent among patients with low ADAMTS13 levels despite that could not found a statistically significant association between mortality of COVID- (Tiscia et al., 2020) (Sweeney et al., 2021 )(Rodríguez Rodríguez et al., 2021 . This difference could be due to different patient characteristics and/or the different anticoagulation doses used in different studies; also, the small sample size in all studies could impact the interpretation.

The definite mechanism of abnormal VWF/ADAMTS13 axis contribution to disease progression and mortality is not well understood. Meijenfeldt et al. reported that low ADAMT13 levels were associated with the need for mechanical ventilation of COVID-19, which is consistent with our findings. Meanwhile, they reported that mortality was associated with decreased ADAMTS13 activity, which is in contrast to our results (von Meijenfeldt et al., 2021) . Dushianthan et al. also reported that ADAMTS13 deficiency was associated with an increased risk for mechanical ventilation by 7.57, which is comparable to our findings (Dushianthan et al., 2021) . Here, the frequency of death was more frequent among patients with low ADAMTS13 levels despite that we could not find a statistically significant association between mortality of COVID-19 and low ADAMT13 activity; this finding is in contrast to the results of some other studies (Tiscia et al., 2020 ) (Sweeney et al., 2021 ) (Rodríguez Rodríguez et al., 2021 . This difference could be due to different patient characteristics and/or the different anticoagulation doses used in different studies; also, the small sample size in all studies could impact the interpretation.

The definite mechanism of abnormal VWF/ADAMTS13 axis contribution to disease progression and mortality is not well understood. Meijenfeldt et al. reported that low ADAMT13 levels were associated with the need for mechanical ventilation of COVID-19, which is consistent with our findings. Meanwhile, they reported that mortality was associated with decreased ADAMTS13 activity, which is in contrast to our results (von Meijenfeldt et al., 2021) . Dushianthan et al. also reported that ADAMTS13 deficiency was associated with an increased risk for mechanical ventilation by 7.57, which is comparable to our findings (Dushianthan et al., 2021) .

Several variables were recognized as a risk factor for poor outcome of COVID-19. Male gender, older age, obesity and comorbidities like acute kidney injury, COPD, diabetes, hypertension, CVD, cancer, smoking, increased D-dimer, are all distinct patient characteristics associated with risk of fatal COVID-19 outcomes (Dessie, Z.G.et al; In severe COVID-19, the appropriate anticoagulation strategy is still debatable; COVID-19 may be profoundly hypercoagulable before anticoagulant therapy, yet bleeding complications have also been documented. In COVID-19 non-survivors, von Meijenfeldt et al found that markers of in vivo coagulation and fibrinolysis were higher in patients who received higher levels of care.

Ex vivo thrombin production was also higher in patients in general wards and similar in patients in higher levels of care, despite higher LMWH dosages in patients in higher levels of care (von Meijenfeldt et al., 2021) In our study, anticoagulant therapy was recommended for all patients with severe COVID-19, and the doses of anticoagulants were increased to therapeutic levels if further deterioration was observed. Additionally, we observed a substantial link between ADMATS13 activity and anticoagulant use; This leads us to believe that early initiating and increasing anticoagulation to therapeutic levels in deteriorating severe COVID-19 patients may avert deteriorating conditions and minimize the need for ICU admission and mechanical ventilation.

According to the linear regression model, we could not find an association between D-dimer concentration and ADAMTS13 activity; this was in opposition to Tiscia et al., who reported an independent association between D-dimer concentration at admission (P = 0.0145) and age (P= 0.0036) and ADAMTS13 activity levels (Tiscia et al., 2020) . This difference could be attributed to different patient characteristics in both studies. COVID-19 infection is associated with exaggerated immune response, activated macrophages, and release of several pro-inflammatory cytokines, including TNF-α, IL-6, IL-8, and IL-1β. Also, the interaction between viral S protein and ACE-2 could activate platelets and enhance their inflammatory response and prothrombic action (Argañaraz et al., 2020) .

Two mechanisms can facilitate thromboembolic manifestations. Firstly, by the passage of different pro-inflammatory mediators generated in pulmonary tissue to the blood, inflammatory mediators such as IL-6 and TNF-α activates endothelial cells, facilitate platelet and monocytes aggregation, and increase the expression of tissue factor (TF) glycoprotein, which in turn will trigger the coagulation cascade leading to thrombus formation. The second mechanism is mediated by decreased ADAMTS13 activity by the inhibitory effect of pro-inflammatory mediators such as C-reactive protein, IL-6, and IL-1β and VWF accumulation in the plasma (Argañaraz et al., 2020) .

Several studies showed that COVID-19 with microangiopathy had an abnormal (Escher et al., 2020) . But Nazy et al. reported that ADAMTS13 activity was not severely impaired among critically ill COVID-19 patients, and increased VWF/ADAMTS13 ratio is more likely secondary to microthrombotic complications compounded with platelet-activating immune complexes (Nazy et al., 2021) .

The cytokine storm is the hallmark of severe COVID-19 pathogenesis , and previous research has revealed that inflammatory cytokines activate the endothelium, resulting in the exocytosis of endothelial WBPs and consequently VWF (Chen J et al; .; in the current study, there was a decrease in ADAMTS13 activity with increasing severity of COVID-19, which could be attributed to the massive production of cytokines, endothelial activation with subsequent exocytosis of WBPs and VWF. The association between Increasing COVID-19 severity and low ADAMT13 activity was also confirmed by other studies (Ward et al., 2021) , (Rovas et al., 2021) .

Increased VWF in the plasma is usually accompanied with decreased levels of ADAMT13 due to its consumption while cleaving ultra-large VWF multimers (Philippe et al., 2021) .

While Doevelaar et al. had reported the absence of ADAMT13 deficiency among COVID-19 cases included in their study, however, there was a significant decrease in ADAMTS13/von Willebrand factor antigen ratio; this was explained by the production of excess VMF that exceeded the proteolytic capacity of ADAMTS13, resulting in its deficiency (Doevelaar et al., 2021) . Meanwhile, Bashir and her colleagues proposed that increased secretion of VWF and decreased ADAMT13 activity could be mediated by hyperferritinemia and consequently inducing pathologic immune activation, thrombosis, and organ damage (Bashir et al., 2021) .

It was demonstrated that mortality is significantly associated with IL-6 levels (Ruan et al., 2020) .

Notwithstanding that in our study, IL-6 was not related to mortality or ADAMTS13 deficiency, while AST and ALT were significantly associated with low ADAMTS13 activity, but most patients had normal or mildly increased laboratory findings. However, IL-6 was measured in a few patients, which could affect the accuracy of these findings, but they also could suggest that ADAMT13 activity is less likely to be low due to its inhibition by IL-6 or impaired production, but mostly it could be due to its consumption while cleaving VWF (X. Zheng et al., 2002) (Bernardo et al., 2004) .

Another explanation is proposed by Henry et al., who reported complement system hyperactivation characterized by a significant increase of C3a, and C3a/C3 and sC5b-9/C3 ratios, and induction of inflammation, endothelial damage, and coagulation among severe COVID-19 patients (Henry et al., 2021) . They also reported a negative correlation with ADAMTS13 activity, suggesting the role of complement system hyperactivation and ADAMTS13 deficiency in CAC (Henry et al., 2021) .

Hyperinflammation and pro-coagulation were observed among COVID-19 patients suggesting a harmful effect of SARS-CoV-2 on endothelial cells. Endothelial damage may be provoked by various mechanisms directly by binding the virus to endothelial cells and promoting cell apoptosis, or indirectly through binding Ang II to A1T receptor on endothelial cells, promoting coagulopathy, microvascular thrombosis, and hypofibrinolysis (Iwasaki et al., 2021) .

Accumulation of Ang II in the lung is also associated with enhanced plasminogen activator inhibitor-1 (PAI-1) genetic expression. PAI-1 promotes thrombosis and inhibits fibrinolysis by inhibition of urokinase plasminogen activator (uPA) and tissue plasminogen activator (tPA), leading to vascular microthrombosis in COVID-19 patients (Bernard et al., 2021) .

Endothelial cells of severe COVID-19 patients can be activated by elevated pro-inflammatory cytokines such as IL-6 and TNF-α. Elevated VMF with reduction of ADAMT13 activity was detected among ICU-admitted patients and associated with thrombotic microangiopathy (Bonaventura et al., 2021) . Pericytes apoptosis mediated by SARS-CoV-2 is also suggested in microvascular dysfunction and coagulability caused by COVID-19 (Evans et al., 2020) .

Here, we also demonstrated for the first time that the time to viral clearance is longer among patients with low ADAMTS13 activity despite not significant, which could be explained by the sample size limitation and the role of confounding factors among presented patients. This could correspond to increased risk of disease severity, coagulation, and recovery among COVID-19 patients with low ADAMTS13 levels and highlight the importance of studying the virologic response in the presence of abnormal coagulation biomarkers for better prognosis of COVID-19

patients.

An experimental study studied the role of ADAMTS13 and recombinant ADAMTS13 (rADAMTS13) in mice with intracerebral hemorrhage (ICH)-induced brain injury and found that rADAMTS13 was associated with decreased levels of different chemokines and cytokine such as IL-6, reduced activation of neutrophils and microglial cells. The anti-inflammatory and brain-protective effect of rADAMTS13 was reversed by rVWF (Cai et al., 2015) . These findings emphasize the importance of rADAMTS13 in regulating pathological inflammation and coagulation. Furthermore, rADAMTS13 could be suggested as a potential treatment for severe COVID-19 to facilitate the degradation of ultra-large VWF and correct an imbalanced ADAMTS13/VMF axis.

In our study, Patients with lower ADAMTS13 activity were more frequently admitted to the ICU than those with normal activity, but the correlation was not statistically significant. This observation could be related to the early and upgrading use of anticoagulation in severe cases.

Plasma exchange with ADAMT13 replacement could be beneficial in COVID-19 patients to provide passive immunity, treat possible TTP and ADAMT13 deficiency, and remove inflammatory cytokines (Furlan M, Robles R, Morselli B, Sandoz P, 1999) (Tanne, 2020) .

These findings suggest the beneficial prognostic value of measuring ADAMT13 activity to predict disease severity and outcomes; it is recommended to measure ADAMT13 and VWF during the diagnosis of COVID-19 patients with suspected microangiopathy.

The limitations of our study include possible bias and intrinsic confounders; this was a retrospective study that could only study the correlation, but not the causation, so larger randomized clinical trials are needed to investigate the causal relationship between ADAMTS13 activity and COVID-19. Another limitation is that the male gender was more dominant, affecting the interpretation of our results as previous studies showed that the male gender is associated with more severe COVID-19 outcomes. We also recommend the measurement of different complement proteins and cytokines, which could have a vital role in altering the VWF/ADAMTS13 axis.

In conclusion, throughout the study of the relationship between ADAMTS13 activity and COVID-19 pathophysiology, presentation, severity, and mortality, we observed a link between low ADAMTS13 activity and the development of pneumonia, the severity of COVID-19, need for mechanical ventilation, and the use of anticoagulants. While there was no significant link between mortality and ADAMTS13 levels. More research is required in order to determine the prognostic usefulness of the VWF/ADAMTS13 axis in COVID-19 patients. Furthermore, we believe that rADAMTS13 could provide a novel therapeutic strategy for severe COVID19. Yadav for their help and support. We would like to express our gratitude to the Medical Agency for Research and Statistics (MARS) for their cooperation and editorial support.

The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the NMC Central scientific committee (NMCHC/CSC/2020/0033), NMC Regional Ethics committee (NMC/RREC/AUH/2020/0017), and Regional Research Ethics Committee, department of health, Abu Dhabi, UAE number (DOH/CVDC/2020/2311).

This is a retrospective study; all Patients Identifiers were removed during data collection process, with complete protection of patients' privacy. This study was conducted according to the Declaration of Helsinki. and approved from IRB(s); the NMC Central scientific committee (NMCHC/CSC/2020/0033), NMC Regional Ethics committee (NMC/RREC/AUH/2020/0017), and Regional Research Ethics Committee, department of health, Abu Dhabi, UAE number (DOH/CVDC/2020/2311).

Data can be available upon request from the first and corresponding author folds, when compared to normal ADAMTS13 activity patients (OR= 4.75, .02],

Based on ADAMTS13 Level showed severity outcome had been increased significantly among patients with ADAMTS13 deficiency by 6.50 folds, increase when compared to normal ADAMTS13 activity patients (OR= 6.50, ], p<0.001),

Level Showed that it had been increased significantly among patients with ADAMTS13 deficiency by 4.1 folds increase when compared to normal ADAMTS13 activity patients (OR= 4.10, ], p=0.024),

showed that use of anticoagulants had been increased significantly among patients with ADAMTS13 deficiency by 8 folds increase when compared to normal ADAMTS13 activity patients (OR=8.00, , p<0.001)

Activity showed non-significantly longer median time to viral clearance in COVID-19 patients with low ADAMTS13 level compared to those with normal ADAMTS13 activity (20 days, 95% CI: [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] vs. 17 days, days, p=0.08, Log rank= 3.1) Abbreviations: ADAMTS 13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), (CRP (C Reactive protein), LDH (lactate dehydrogenase), ALT (The alanine aminotransferase), AST (aspartate aminotransferase), IL-6 (interleukin 6)

Phosphatidylserine inside out: A possible underlying mechanism in the inflammation and coagulation abnormalities of COVID -19

Ultralarge multimers of von Willebrand factor form spontaneous high-strength bonds with the platelet glycoprotein Ib-IX complex: Studies using optical tweezers

Secretion of von Willebrand Factor and Suppression of ADAMTS-13 Activity by Markedly High Concentration of Ferritin

Endothelium infection and dysregulation by sars-cov-2: Evidence and caveats in covid-19

Effects of inflammatory cytokines on the release and cleavage of the endothelial cell-derived ultralarge von Willebrand-factor multimers under flow

In vitro hypercoagulability and ongoing in vivo activation of coagulation and fibrinolysis in COVID-19 patients on anticoagulation

Endothelial dysfunction and immunothrombosis as key pathogenic mechanisms in COVID-19

The emerging spectrum of cardiopulmonary pathology of the coronavirus disease 2019 (COVID-19): Report of 3 autopsies from Houston, Texas, and review of autopsy findings from other United States cities

Recombinant ADAMTS 13 Attenuates Brain Injury after Intracerebral Hemorrhage

Pulmonary postmortem findings in a series of COVID-19 cases from northern Italy: A two-centre descriptive study

Inflammation, von Willebrand factor, and ADAMTS13

Shear-induced disulfide bond formation regulates adhesion activity of von Willebrand factor

Unraveling the scissile bond: How ADAMTS13 recognizes and cleaves von Willebrand factor

Mortality-related risk factors of COVID-19: a systematic review and meta-analysis of 42 studies and 423,117 patients

Multimer Formation Contributes to Immunothrombosis in Coronavirus Disease

ADAMTS-13 rapidly cleaves newly secreted ultralarge von Willebrand factor multimers on the endothelial surface under flowing conditions

Predictive Role of Haematological Determinants on Outcomes of Critically Ill COVID-19 Patients Admitted to Intensive Care Unit

ADAMTS13 activity, von Willebrand factor, factor VIII and D-dimers in COVID-19 inpatients

Endothelial dysfunction in COVID-19: A position paper of the ESC Working Group for Atherosclerosis and Vascular Biology, and the ESC Council of Basic Cardiovascular Science

ADAMTS13 activity to antigen ratio in physiological and pathological conditions associated with an increased risk of thrombosis

COVID-19-associated coagulopathy

Purification of human von Willebrand factor-cleaving protease and its identification as a new member of the metalloproteinase family

Von Willebrand factor: Molecular size and functional activity

Aetiology and pathogenesis of thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome: The role of von Willebrand factor-cleaving protease

Von Willebrand factor-cleaving protease in thrombotic thrombocytopenic purpura and the hemolytic-uremic syndrome

Recovery and half-life of von Willebrand factor-cleaving protease after plasma therapy in patients with thrombotic thrombocytopenic purpura

The Role of von Willebrand Factor in Vascular Inflammation: From Pathogenesis to Targeted Therapy

Management of a covid-19 patient during ECMO: Paying attention to acquired von Willebrand syndrome

Complement levels at admission as a reflection of coronavirus disease 2019 (COVID-19) severity state

Establishment of the WHO 1st International Standard ADAMTS13, plasma (12/252): Communication from the SSC of the ISTH

Inflammation Triggered by SARS-CoV-2 and ACE2 Augment Drives Multiple Organ Failure of Severe COVID-19: Molecular Mechanisms and Implications

VWF73, a region from D1596 to R1668 of von Willebrand factor, provides a minimal substrate for ADAMTS-13

Thrombotic thrombocytopenic purpura

Acute portal vein thrombosis in SARS-CoV-2 infection

ADAMTS-13-VWF axis in sickle cell disease patients

The role of ADAMTS-13 in the coagulopathy of sepsis

Mutations in a member of the ADAMTS gene family cause thrombotic thrombocytopenic purpura

Shear stress and the role of high molecular weight von Willebrand factor multimers in thrombus formation

Genomic characterisation and epidemiology of 2019 novel coronavirus: Implications for virus origins and receptor binding

A relative ADAMTS13 deficiency supports the presence of a secondary microangiopathy in COVID 19

The role of ADAMTS13 testing in the diagnosis and management of thrombotic microangiopathies and thrombosis

Increased von Willebrand factor (vWf) binding to platelets associated with impaired vWf breakdown in thrombotic thrombocytopenic purpura

Clinical Management of the Critically ill COVID-19 Patient. United Arab Emirates-Ministry if Health

Platelet-activating immune complexes identified in critically ill COVID-19 patients suspected of heparin-induced thrombocytopenia

The role of ADAMTS-13 and von Willebrand factor in cancer patients: Results from the Vienna Cancer and Thrombosis Study

ADAMTS 13 deficiency is associated with abnormal distribution of von Willebrand factor multimers in patients with COVID-19

ADAMTS-13 assays in thrombotic thrombocytopenic purpura

Von Willebrand factor collagen -binding capacity predicts in -hospital mortality in COVID -19 patients: Insight from VWF / ADAMTS13 ratio imbalance

High levels of coagulation factors and venous thrombosis risk: Strongest association for factor VIII and von Willebrand factor

Increased von Willebrand factor antigen and low ADAMTS13 activity are related to poor prognosis in covid-19 patients

Transmission of 2019-nCoV Infection from an Asymptomatic Contact in Germany

Microvascular dysfunction in COVID-19: The MYSTIC study

Clinical predictors of mortality due to COVID-19 based on an analysis of data of 150 patients from Wuhan

Von Willebrand factor: Looking back and looking forward

Thrombotic Thrombocytopenic Purpura: Pathogenesis, Diagnosis, and Potential Novel Therapeutics

ADAMTS-13 in the Diagnosis and Management of Thrombotic Microangiopathies

Sheardependent changes in the three-dimensional structure of human von Willebrand factor

ADAMTS-13 and von Willebrand factor: A dynamic duo

Inducible secretion of large, biologically potent von Willebrand factor multimers

The clinical utility of ADAMTS13 activity, antigen and autoantibody assays in thrombotic thrombocytopenic purpura

Elevated plasma factor VIII enhances venous thrombus formation in rabbits: Contribution of factor XI, von Willebrand factor and tissue factor

Low ADAMTS13 Activity Correlates with Increased Mortality in COVID-19 Patients

Covid-19: FDA approves use of convalescent plasma to treat critically ill patients

Reduction of ADAMTS13 Levels Predicts Mortality in SARS-CoV-2 Patients

COVID-19 and thrombotic microangiopathies

Second international collaborative study evaluating performance characteristics of methods measuring the von Willebrand factor cleaving protease (ADAMTS-13)

Antibodies to von Willebrand factor-cleaving protease in acute thrombotic thrombocytopenic purpura

Human endothelial cells synthesize and release ADAMTS-13

SARS-CoV-2/COVID-19: Viral Genomics, Epidemiology, Vaccines, and Therapeutic Interventions

Weibel-Palade bodies: A window to von Willebrand disease

Prothrombotic changes in patients with COVID-19 are associated with disease severity and mortality

& Irish COVID-19 Vasculopathy Study (iCVS) investigators. (2021). ADAMTS13 regulation of VWF multimer distribution in severe COVID-19

The Impact of COVID-19 Disease on Platelets and Coagulation

ADAMTS13 and von Willebrand factor interactions

Structure of von Willebrand Factor-cleaving Protease (ADAMTS13), a Metalloprotease Involved in Thrombotic Thrombocytopenic Purpura

ADAMTS13 and von willebrand factor in thrombotic thrombocytopenic purpura

ADAMTS13 and TTP