Presently, there is limited literature discussing the possible pathophysiology, risk factors and treatments in long COVID.26
Long COVID may be driven by long-term tissue damage (e.g., lung, brain and heart) and pathological inflammation (e.g., from viral persistence, immune dysregulation and autoimmunity). The associated risk factors may include female sex, more than five early symptoms, early dyspnea, prior psychiatric disorders, and specific biomarkers (e.g., D-dimer, C-Reactive Protein (CRP) and lymphocyte count), although more research is required to substantiate such risk factors. While preliminary evidence suggests that personalized rehabilitation training may help certain long COVID cases, therapeutic drugs repurposed from other similar conditions, such as myalgic encephalomyelitis or chronic fatigue syndrome, postural orthostatic tachycardia syndrome, and mast cell activation syndrome, also hold potential. In sum, this review hopes to provide the current understanding of what is known about long COVID.26
POSSIBLE RISK FACTORS (BIOMARKERS)26
- Elevated blood urea nitrogen (BUN) and D-dimer levels were found to be risk factors for pulmonary dysfunction among survivors of COVID-19 at three-month, post-hospital discharge.27
- Other studies have shown that COVID-19 pulmonary lesions at two-month post-admission were associated with elevated systemic inflammatory biomarkers, such as D-dimer, interleukin-6 (IL-6) and CRP.28,29
- Systemic inflammatory biomarkers (e.g., CRP, procalcitonin and neutrophil count) also correlated with radiological abnormalities of the heart, liver and kidney in a 2- to 3-month follow-up study of discharged COVID-19 patients.30
- In another study, increased D-dimer and CRP levels and decreased lymphocytes were more common in COVID-19 survivors who developed persistent symptoms than their fully recovered counterparts.31
- Another report also found that lymphopenia correlated with chest tightness and heart palpitations, whereas elevated troponin-1 correlated with fatigue, among sufferers of long COVID.32
Therefore, changes in levels of D-dimer, CRP and lymphocyte appeared consistent in a few studies, and may serve as potential biomarkers of long COVID.
When individuals infected with the SARS-CoV-2 virus are not isolated, they can spread the virus. The solution to containing disease spread is the quick identification of infected individuals followed by quarantine. This is especially important for pre-symptomatic and asymptomatic individuals who may unknowingly spread the virus. Studies have shown that a positive or negative antigen test might be a useful proxy for the risk for being infectious,33 and that infected individuals are more likely to transmit the virus when they test positive for the SARS-CoV-2 antigen.34 Additionally, the implication of a false positive RT-PCR result can include unnecessary treatment and investigation, missing or delayed surgery, unnecessary isolation and contact tracing, and increased risk of exposure when placed with other COVID-19 patients.25
By testing patients and providing results quickly, antibiotics can be withheld and antivirals can be prescribed only where appropriate. Physician awareness of a rapid diagnosis of COVID-19 decreases antibiotic use.
Rapid Diagnostic Tests (RDTs) are used for the qualitative detection of either antigen or antibody biomarkers of the SARS-CoV-2 virus.33 Rapid diagnostic testing can be performed at the point of care (POC), workplace, school or home.19 Widespread RDT deployment is valuable for population screening and surveillance for effectively limiting the spread of COVID-19.19,20 RDTs are most effective for use in POC settings and for performing seroprevalence studies.36