The aftermath of COVID
Between 5-50% of COVID-19 survivors are estimated to develop long-COVID (LC), which includes diverse symptoms that can last months after the initial SARS-CoV-2 infection. These symptoms can involve the entire body, including the respiratory, neurological, cardiovascular, and gastrointestinal systems, and can be debilitating, greatly affecting the quality of life of individuals with LC and their families. Although the symptoms are well described, the cause of LC remains unclear, and consequently, many patients are undiagnosed and not properly treated. Identification of LC- specific biomarkers is therefore paramount to improving diagnosis and clinical management of the syndrome.
Understanding the current literature
The HLI’s Estefanía Espín, a Ph.D. student in Dr. Scott Tebbutt’s lab, and a Mitacs Accelerate intern at the PROOF Centre of Excellence, recently undertook a scoping review to describe the molecular and cellular biomarkers identified to date with potential use for diagnosis or prediction of LC. A scoping review is a way to present an overview of the large and diverse body of literature surrounding long-COVID research. This review was recently published at eBioMedicine, part of the Lancet Discovery Science series.
Conducted using the Joanna Briggs Institute (JBI) Methodology for Scoping Reviews, Espín, and colleagues, including Dr. Chengliang Yang at PROOF, performed a search in the MEDLINE and EMBASE databases, as well as in the grey literature for original studies, published until October 5th, 2022, reporting biomarkers identified in participants with LC symptoms (from all ages, ethnicities, and sex), with a previous infection of SARS-CoV-2.
Potential biomarkers for long-COVID
In total, 23 cohort studies were identified, involving 2163 LC patients [median age 51·8 years, predominantly female sex (61·10%), white (75%), and non-vaccinated (99%)]. A total of 239 candidate biomarkers were identified, consisting mainly of immune cells, immunoglobulins, cytokines, and other plasma proteins. The candidate biomarkers compiled in the review point to LC resulting from an uncontrolled immune response, triggered by the initial viral infection, and characterized by specific immune signatures.
“An optimal biomarker should be objectively quantifiable, sensitive and specific, easily adapted into routine clinical practice, and detectable in easily accessible specimens. The pool of candidate biomarkers reported in my review were detected in blood samples and therefore could be established in quantifiable assays for clinical practice.”
Given the large number of biomarkers identified, more work is needed to identify those which could be used to stratify risk at SARS-CoV-2 infection onset, confirm LC diagnosis, and/or subset patients for specific interventions. This is work that Estefanía will continue during her Ph.D. project.
“As I continue my Ph.D. project, I will conduct qualitative research to inquire about the perspectives of long-COVID patients and clinicians about their needs in biomarkers research. Thus, the scoping review together with the qualitative research will allow me to have a complete landscape about LC biomarkers resulting in a relevant clinical question to be answered by biomarker development from molecular and cellular data.”Estefanía Espín, PhD candidate
Dr. Scott Tebbutt’s lab