Review article: Hematologic Abnormalities Associated with Post-Acute COVID-19 Sequelae or “long-COVID”- a Systematic Review
Jamie-lee Brundyn, Jamie Gillan, Indu Singh
Int. J. Bio. Lab. Sci 2022(11)1:23-42【PDF】
Objective: SARS-CoV-2 emerged late 2019 and quickly spread globally. Acute COVID-19 effects were quickly elucidated; however, some patients were found to suffer from persistent symptoms in the absence of an acute infection. This places unnecessary pressure on healthcare systems and affects patient quality of life. Literature indicated lymphopenia, hyperferritinemia and coagulopathies were common among those with persistent symptoms. This systematic review aims to summarize the association between these hematologic abnormalities and long-COVID.
Methods: A systematic search of five electronic databases, PubMed, Google Scholar, Science Direct, Griffith University library and Cochrane, was conducted using specified search terms described in the methods section. Studies were refined using the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) tool. Data was retrieved from studies that passed the risk of bias (ROB) and met the inclusion and exclusion criteria, as follows; number of participants (≥10), hematologic testing, timing of testing, and studies with full text available in English.
Results: The search strategy identified 14 studies that passed the ROB, met the inclusion and exclusion criteria, and were selected for the systematic review. Though some patients experiencing long-COVID had lymphopenia, hyperferritin-emia and coagulopathies, there was inconsistencies found. Some patients with long-COVID had limited evidence of hematologic abnormalities.
Discussion: Lymphopenia was a frequent anomaly identified in post-acute COVID, however, not exclusive to long-COVID patients. New research has shown the absence of specific T and B lymphocyte subsets may be exclusive to long-COVID patients, along with the sustained activation of other immune cells. Evidence has also emerged showing sustained inflammation beyond the acute infection in long-COVID patients. Coagulopathies have been shown to persist due to an elevated D-dimer in post-acute COVID-19 analyses.
Conclusion: There is evidence of hematologic features that are exclusive to long-COVID, however, research is still limited. The cause and effect of these abnormalities are yet to be determined. With future directions, further supporting evidence may emerge elucidating the potential hematological causes and mediators of long-COVID.
Key words: Long-COVID, Persistent symptoms, Lymphopenia, Iron dysregulation, Coagulopathy.