Antiplatelet therapy prior to COVID-19 infection impacts on patients mortality: a propensity score-matched cohort study

One of the major pathomechanisms of COVID-19 is the interplay of hyperinflammation and disruptions in coagulation processes, involving thrombocytes. Antiplatelet therapy (AP) by anti-inflammatory effect and inhibition of platelet aggregation may affect these pathways. The aim of this study was to investigate if AP has an impact on the in-hospital course and medium-term outcomes in hospitalized COVID-19 patients. The study population (2170 COVID-19 patients: mean ± SD age 60 ± 19 years old, 50% male) was divided into a group of 274 patients receiving any AP prior to COVID-19 infection (AP group), and after propensity score matching, a group of 274 patients without previous AP (non-AP group). Patients from the AP group were less frequently hospitalized in the intensive care unit: 9% vs. 15%, 0.55 (0.33–0.94), developed less often shock: 9% vs. 15%, 0.56 (0.33–0.96), and required less aggressive forms of therapy. The AP group had more coronary revascularizations: 5% vs. 1%, 3.48 (2.19–5.55) and strokes/TIA: 5% vs. 1%, 3.63 (1.18–11.2). The bleeding rate was comparable: 7% vs. 7%, 1.06 (0.54–2.06). The patients from the AP group had lower 3-month mortality: 31% vs. 39%, 0.69 (0.51–0.93) and didn’t differ significantly in 6-month mortality: 34% vs. 41%, 0.79 (0.60–1.04). When analyzing the subgroup with a history of myocardial infarction and/or coronary revascularization and/or previous stroke/transient ischemic attack and/or peripheral artery disease, AP had a beneficial effect on both 3-month: 37% vs. 56%, 0.58 (0.40–0.86) and 6-month mortality: 42% vs. 57%, 0.63 (0.44–0.92). Moreover, the favourable effect was highly noticeable in this subgroup where acetylsalicylic acid was continued during hospitalization with reduction of in-hospital: 19% vs. 43%, 0.31 (0.15–0.67), 3-month: 30% vs. 54%, 044 (0.26–0.75) and 6-month mortality: 33% vs. 54%, 0.49 (0.29–0.82) when confronted with the subgroup who had acetylsalicylic acid suspension during hospitalization. The AP may have a beneficial impact on hospital course and mortality in COVID-19 and shouldn’t be discontinued, especially in high-risk patients.

Post-mortem studies have demonstrated the presence of multi-organ thrombosis, even in asymptomatic patients and those on standard thromboprophylaxis 5,13,14 .While fibrin thrombi were observed in small arterial vessels in 87% of the samples analyzed, increased deposition of platelets and megakaryocytes with increased platelet-leukocyte aggregates has also been reported in pulmonary capillaries [15][16][17][18] .The incidence rate of thromboembolic events (e.g., venous thromboembolism, pulmonary embolism, stroke, acute coronary syndrome, bowel and limb ischemia) varies between studies.It is highest in critically ill and mechanically ventilated patients and worsens the prognosis [19][20][21] .The rate of arterial thromboembolism has been estimated at 2.8-8.4% 19 .
The complex relationship between SARS-CoV-2 infection and hemostatic dysfunction observed in COVID-19 patients is still not fully understood, and treatment outcomes remain unsatisfactory 32 .While antithrombotic treatment does not appear to protect against morbidity and mortality, there is a need for effective therapy to reduce the incidence of thromboembolic complications and improve outcomes [33][34][35] .
The aim of the present study was to evaluate the effect of AP treatment prior to COVID-19 infection on the clinical profile, in-hospital course, and short-and medium-term mortality of patients hospitalized with COVID-19.To compare the risk of death among patients with or without prior AP therapy, we conducted a propensity score matching (PSM).

Description of the entire COVID-19 cohort and study groups
The clinical characteristic of the 2170 hospitalized patients with COVID-19 is presented in Table 1.
Based on PSM, the group of 274 patients receiving AP before hospitalization and 274 patients without previous antiplatelet therapy were selected from the study population.Patients were matched 1:1 across each cohort on a propensity score generated by the logistic regression model, adjusting for the following covariates: age, sex, arterial hypertension, heart failure, previous ischemic stroke, renal insufficiency, obesity (body mass index ≥ 30 kg/m 2 ), diabetes mellitus.
Due to the missing data, 2 patients were excluded from the analysis (see Fig. 1 for the flowchart of the study population).The characteristics of two groups of patients (274:274) after PSM are shown in Tables 2 and 3.
Both groups did not differ in demographic parameters.Patients from the AP group had more frequent previous coronary revascularization, previous MI, peripheral artery disease (PAD) and less frequently atrial fibrillation/flutter in comparison with the non-AP group.There were no differences in baseline clinical signs and symptoms apart from higher baseline oxygen saturation in room air.The AP group was receiving much more medical treatment than the non-AP group before hospitalization, concerning angiotensin-converting enzyme inhibitors (ACEIs), β-blockers, calcium blockers and loop diuretics.Among laboratory parameters, patients from the AP group had significantly lower levels of inflammatory markers at admission, including CRP, procalcitonin (minimum and maximum values) registered during hospitalization in comparison to the non-AP group.Ferritin as an acute phase marker was also lower in the AP group at admission as well as during hospital stay in comparison to the non-AP group.There were no differences in IL-6 levels.

The association of AP treatment with the in-hospital course
Patients from the AP group did not differ significantly with respect to the non-AP group in terms of in-hospital mortality 53 (19%) vs. 64 (23%), OR (95% CI) 0.79 (0.52-1.19).However, patients from the AP group developed fewer shocks, were less frequently hospitalized in the intensive care, and the AP group and was less frequently treated with mechanical ventilation.The AP group had more coronary interventions, including angiography, revascularizations, and also suffered more strokes.The bleeding rate was comparable in both groups.The in-hospital course and therapies applied during the hospitalization after PSM are shown in Table 4.

Discussion
The results of our study show that AP may have beneficial impact on the in-hospital course and mediumterm mortality of patients hospitalized with COVID-19.Moreover, AP did not increase the number of hemorrhagic complications.Importantly we have also found significantly lower inflammatory markers in the AP group, suggesting a potential mechanism in reducing the excessive inflammatory response, underlying the pathophysiology of COVID-19.
The study group consisted of COVID-19 patients hospitalized between 2020 and 2021.These patients faced more aggressive variants of the virus coupled with the absence of a vaccination program at that time.It should be emphasized, that the studied subgroups are characterized by a high number of comorbidities and risk factors, which probably largely determine a worse prognosis, when affected by COVID-19.Hence, AP in high cardiovascular risk groups could offer significant benefits and should be considered in COVID-19 even with more benign viral variants.
The more frequent coronary angiography and revascularization in the AP group may be linked to a higher incidence of pre-hospitalization coronary problems.Still, despite the greater number of comorbidities and vascular events during hospitalization, the overall prognosis was better in the AP group.A doubly robust estimation, with potential confounders, including medical treatment, also showed potential benefits of AP treatment.
Coronary artery disease (CAD) or PAD constitutes an indication for long-term AP therapy as secondary prevention.There were also patients with a history of MI in the non-AP group.The lack of AP treatment or its disconituation can be explained by the use of anticoagulation, according to the European guidelines, which recommend them as the only treatment usually after 12 months since MI 36 .Anticoagulation has been shown to be more effective in preventing thromboembolic events in atrial fibrillation which may also explain the lower number of ischemic strokes and TIA in the non-AP group.Interestingly, a recent study reported that combination of therapeutic dose of heparin with AP did not improve outcome compared with therapeutic doses of heparin alone 29 .
Although AP treatment is a recognized risk factor for major bleeding, especially in long-term observation, in older patients, and without the routine proton-pump inhibitors (PPI) use [37][38][39] , we observed no significant differences in hemorrhagic complications between the groups.The use of PPI, given to one-third of AP-treated patients, may be a contributing factor.
Patients in the AP group were more frequently treated with ACEIs and β-blockers.The result of our study are consistent with large single-center registry in Poland, which found that treatment with ACEIs/ARBs, β-blockers, statins, or AP was associated with lower risk of in-hospital death in patients with COVID-19.Authors did not however studied the effect of AP on medium-term prognosis 38 .
The importance of the inflammatory repsonce in the pathogenesis of cardiac commplications in the course of COVID-19 is well established in the have multisystem inflammatory syndrome in children, which is late immune-mediated complication occurring after SARS-CoV-2 infection 40,41 .Thus, beneficial impact of AP on hospital course and mortality in COVID-19 can be explained by anti-inflammatory effects of AP agents [15][16][17][18]42 .
It was proven, that P2Y12 inhibitors (i.e.clopidgrel, ticagrelor, prasugrel) may reduce the platelet-related release of pro-inflammatory markers and the formation of platelet-leukocyte aggregates [15][16][17][18]43 . The can also increase endothelial nitric oxide bioavailability and reduce oxidative stress in patients with CAD 44 .ASA exerts not only anti-inflammatory effects but may have some antiviral activity on the level of viral ribonucleic acids 45 .In some studies, the pre-admission treatment with ASA was associated with better in-hospital outcomes and a reduced need for respiratory support 46 .www.nature.com/scientificreports/

Limitations
The study is a retrospective analysis of a single-center cohort, which may limit its evidence.Despite the PSM, it is possible that some factors not included in the model could impact the outcomes.While the analysis was based on the data about AP prior to the hospitalization, the data about the duration of the treatment prior COVID-19 and in-hospital treatment were not fully gathered.In the majority of cases the treatment during hospitalization www.nature.com/scientificreports/continued the one applied before.Patients were also discharged home with similar medication introduced before admission.Therefore the AP effect could also be the effect of ongoing treatment not only before admission.There were no differences in the use of anticoagulation drugs during hospitalization.Undoubtedly, further prospective studies are needed to verify the clinical value of AP treatment in COVID-19 hospitalized patients and in order to create an optimal medical strategy for SARS-CoV-2 and SARS-CoV-like future infections.
The results of our study show that AP prior to COVID-19 infection may have a beneficial impact on the in-hospital course, mainly driven by the reduction of respiratory complications and intensive care unit admissions.AP may also influence medium-term mortality in COVID-19 and shouldn't be discontinued, especially in the high-risk patients.

Study population
We included consecutive patients ≥ 18 years, hospitalized in the University Hospital, Wroclaw (Poland), between March 2020 and May 2021, with COVID-19 confirmed by polymerase chain reaction testing of a nasopharyngeal sample or a positive blood antigen test.The study cohort was divided into two groups according to AP status.a. Patients receiving any antiplatelet treatment (acetylsalicylic acid (ASA) and/or clopidogrel/ticagrelor/ prasugrel) prior to COVID-19 infection (AP group) b.Matched patients without antiplatelet treatment (non-AP group).Table 3. Laboratory parameters in the studied groups.The variables are presented as the mean, and standard deviation for normally distributed variables, whereas median with interquartile range (IQ) for non-normally distributed variables.AP antiplatelet treatment, Aspat aspartate transaminase, Alat alanine transaminase, GGTP gamma-glutamyltransferase, NT-proBNP N-terminal pro-type brain natriuretic peptide, CRP C-reactive protein, IL-6 interleukin-6.

Statistics
Categorical variables were presented as numbers and percentages, the numerical variables as the mean and standard deviation for normally distributed variables, whereas median with interquartile range (IQ) for nonnormally distributed variables.The Shapiro-Wilk test was used to verify the distribution of continuous variables, and the Mann-Whitney U test was applied for group comparison.The chi-square test or Fisher's exact test was used to compare qualitative variables.PSM was performed using the match function of the MatchIt R package.The function parameters were set to the logistic regression model, with adjustments for the covariates.Patients were matched using the nearest neighbor technique.Balanced pairs of patients in relation to variables that could impact the outcome were selected from the entire population of 2168 patients.
The association of AP treatment with the in-hospital course was tested with logistic regression model.Kaplan-Meier curves with time to death were constructed to estimate the effect of antiplatelet treatment on allcause 90, and 180-day mortality.Differences in survival rates were tested with the log-rank test.For the doubly robust estimation, the associations between survival and potential clinical confounder, including other medical treatments, were tested using the univariable and multivariable Cox proportional hazard regression model.The univariable model was performed on the variables (demographics, co-morbidities, clinical signs and symptoms at admission and treatment applied before and during hospitalization) that showed significant association with mortality in COVID-19 in previous studies (age, gender, BMI), which differed between the AP and non-AP groups and which were not interdependent.The multivariable model included variables that were statistically significant and associated with univariable models.
All analyses were performed using Statistica v.13.3 (TIBCO Software Inc., Palo Alto, CA, USA) except PSM, which was performed with the MatchIt R package.The P values < 0.05 were considered statistically significant.

Figure 1 .
Figure 1.Flowchart of the study population.

Table 1 .
Baseline characteristic of the entire COVID-19 cohort.The numerical variables are presented as mean and standard deviation.

Table 2 .
The comparison of the study groups.The numerical variables are presented as mean and standard deviation.

Table 4 .
Analyzed variables (demographics, laboratory measurements, comorbidities) were retrospectively collected from the electronic hospital system.The study protocol for the COLOS (COronavirus in the LOwer Silesia registry) study has been approved by the Institutional Review Board and Ethics Committee at the Wroclaw Medical University, Wroclaw, Poland (No.: KB-444/2021).The Bioethics Committee approved the publication of fully anonymized data.Written informed consent to participate in the study was waived to limit unnecessary contact In-hospital course and therapies applied during the hospitalization in the studied groups.AP antiplatelet treatment, OR odds ratio, CI confidence interval.