Table 1.
A summary of some biomarkers discussed in this paper. These biomarkers are prone to being influenced by a variety of variables. There is also a shortage of studies exploring Serum COVID-19 Concentrations.
| Name | Role | Approx. Healthy Concentration (μg/mL) | Serum Concentration in COVID-19 (μg/mL) |
|---|---|---|---|
| CRP | A protein which mediates inflammation in the body [35]. IL-6 is the main inducer for CRP production, with IL-1 enhancing it [36]. |
Serum median: | Severe: |
| 0.8 [35] | ≥41.8 [37] | ||
| IL-1β | A proinflammatory cytokine that helps with the production of synoviocytes [38] and proteases for inflammation [39]. | Serum: | Mild range: 1.729 × 10−5 – 3.422 × 10−5 Severe range: 2.589 × 10−5 – 4.718 × 10−5 [40] |
| 6.46 × 10−6 – 2.696 × 10−5 [40] | |||
| IL-4 | Immunoregulatory cytokines that help regulate antibody production, hematopoiesis, aids in the formation of the effector T-cell response [41]. | Serum: 3.486 × 10−5 ± 2.442 × 10−5 [40] |
Mild range: 3.251 × 10−5 – 5.550 × 10−5 Severe range: 3.646 × 10−5 – 1.0379 × 10−4 [40] |
| IL-6 | Most released cytokine by activated macrophages [42]. Induces an acute phase response | Serum: 9.0 × 10−7 – 1.0 × 10−5 [43,44] | Severe: ≥5.5 × 10−5 High likelihood of mortality: ≥8.0 × 10−5 [45] |
| lL-8 | A chemokine (CXL8) that is linked to the progression of ARDS [46]. Has a key role in neutrophil recruitment [47] |
Serum: 1.29 × 10−5 ± 1.393 × 10−5 [48] |
Severe: ≥5.0 × 10−5 [49] |
| IL-10 | Inhibits the activity of Th1, natural killer cells, and macrophages. All these are used for pathogen expulsion [50]. | Serum: 2.21 × 10−6 – 6.02 × 10−6 [40] |
Mild range: 3.32 × 10−6 – 4.16 × 10−6 Severe range: 6.30 × 10−6 – 8.05 × 10−6 [40] |
| D-dimer | A protein fragment produced by fibrinolysis (clot breakdown) [51]. | Serum: ≤0.5 [52] |
Survivors median: 1.02 Non-survivors median: 6.21 [52] |
| TNFα | A potent pleiotropic cytokine that participates in cell proliferation, differentiation and apoptosis [53,54]. | Serum: 1.12 × 10−5 ± 7.31 × 10−6 [48] | Not yet established |
| l-glutamate | An abundant excitatory neurotransmitter implicated in several neurodegenerative diseases [55]. | Plasma: 0.74–14.7 Saliva: 3.4 × 10-2 ± 2.6 × 10-2 Urine: 4.855 × 102–2.7072 × 103 creatinine [55] |
Not yet established |