Hematological abnormalities and ABO blood groups: unraveling their confluences in patients with long COVID

Long COVID is characterized by persistent symptoms after the acute phase of SARS-CoV-2 infection. Although the etiology of symptoms remains unclear, evidence suggests the involvement of immunoinflammatory processes and a possible impact of ABO blood groups on susceptibility to COVID-19 infection and disease severity. Our aim is to analyze the interaction between ABO groups and hematologic abnormalities of individuals with persistent symptoms after COVID-19 infection. We included patients aged ≥ 18 years who were hospitalized with COVID-19 and presented symptoms after 90 days of diagnosis. We excluded those who were on anticoagulation before hospitalization for COVID-19 or at the time of inclusion. Patients were recruited from July 12, 2022, to September 4, 2023 at the Instituto Nacional de Infectologia Evandro Chagas (INI) in Rio de Janeiro after approval by the INI CEP (CAAE3244942.4.1001.5262). We identified 223 hospitalized patients with symptoms of long COVID. In the end, 220 participants were analyzed, with a median follow-up and IQR of 655 days (430-818). The distribution of blood groups was O (113), A (80), B (22) and AB (5). The median age was 58 years and IQR of 47-67, with a frequency of 98 (44.4%) female individuals. 126 patients with hematological alterations were identified: platelet count 10 (4.5%), partial thromboplastin time (PTT) 33 (15%), d-dimer 56 (25.5%) and fibrinogen 81 (36.8%), being more prevalent in women (54%). The most commonly reported symptoms were neurological in 201 (15.7%), psychiatric in 170 (13.3%), and musculoskeletal in 151 (11.8%). We observed no relationship between ABO groups and hematologic alterations. We emphasize that chronic inflammatory events may persist in patients presenting with long-term COVID-19 symptoms. It is believed that ABO blood type does not clearly influence inflammatory responses in Long COVID. Future studies should explore the mechanisms involved in chronic inflammation in Long COVID patients.