This is a mechanistic, observational, prospective, case and control study, to compare platelet aggregation, analyzed by Multiplate-ADP, in hospitalized patients diagnosed with COVID-19 versus healthy controls. Thus will be included 60 patients who present with respiratory symptoms within 72 hours of hospitalization and confirmation of the diagnosis of COVID-19 by laboratory method (RT -PCR and / or positive serology for SARS-CoV-2 - COVID group); this group will be compared to 60 healthy individuals (asymptomatic and with negative SARS-CoV-2 serology), matched by sex and age to the previous group.

There is strong evidence that SARS-CoV-2 infection is associated with atherothrombotic phenomena. However, platelet activity in COVID-19 has not yet been studied.

Thus, the main objective of this project is to evaluate platelet aggregation by the Multiplate-ADP method in hospitalized patients diagnosed with COVID-19, in comparison with the platelet aggregation evaluated by the same method in healthy controls.

Secondary objectives include the assessment of parameters related to coagulation, inflammation, and clinical outcome variables.

This is a mechanistic, observational, prospective, case and control study, which will include 60 patients who present with respiratory symptoms within 72 hours of hospitalization and confirmation of the diagnosis of COVID-19 by laboratory method (RT -PCR and / or positive serology for SARS-CoV-2 - COVID group); this group will be compared to 60 healthy individuals (asymptomatic and with negative SARS-CoV-2 serology), matched by sex and age to the previous group.

Inclusion Criteria:

• Agreement to sign the Free and Informed Consent Form (ICF).
• Case group: patients with up to 72 hours of hospitalization for respiratory symptoms.
• Control group: healthy volunteers, defined as having no history (confirmed or suspected) of COVID-19 or chronic diseases (except hypertension, obesity, dyslipidemia)

Exclusion Criteria:

• Known platelet dysfunction or platelet count <100,000 / µL or> 450,000 / µL;
• Terminal illness;
• Known liver disease or clotting disorder;
• Hematocrit less than 34% or greater than 55%;
• Previous use of antiplatelet agents and / or anticoagulants (except acetylsalicylic acid and prophylactic heparin);
• Patients on invasive mechanical ventilation or receiving high oxygen flow.

Patients with up to 72 hours of hospitalization for respiratory symptoms, tested with RT- PCR for respiratory viruses, will be evaluated for inclusion. Patients with diagnostic criteria for COVID-19 will be considered a case group (COVID-19 group) and will be compared to two other groups: patients hospitalized for respiratory symptoms with a negative test for SARS-CoV-2, and healthy control group.