Investigations

1. Real-time reverse polymerase transcription chain reaction (RT-PCR)

2. CBC

3. Comprehensive metabolic panel

Elevated liver enzymes, total bilirubin, creatinine, and blood urea nitrogen, and hypoalbuminemia are significantly associated with severe disease, and may be useful for predicting disease progression.

Hypokalemia has been reported in 54% of patients. Hypocalcemia has been reported in 63% of patients, and is associated with poor outcomes. Other electrolyte derangements may be present

4. Blood glucose level

5. Coagulation screen

Elevated D-dimer, elevated fibrinogen (and fibrin degradation product), and prolonged prothrombin time are significantly associated with severe disease, and may be useful for predicting disease progression.

A D-dimer test is a blood test that can be used to help rule out the presence of a serious blood clot.

D-dimer is the degradation product of crosslinked (by factor XIII) fibrin. It reflects ongoing activation of the hemostatic system. The reference concentration of D-dimer is < 250 ng/mL, or < 0.4 mcg/mL.

6. Cardiac biomarkers

Elevated creatine kinase-myocardial band (CK-MB), B-type natriuretic peptide (BNP), N-terminal proBNP (NT-proBNP), and troponin are associated with severe disease and mortality, and may be useful for predicting disease progression or survival.

7. Serum C-reactive protein

Elevated C-reactive protein is significantly associated with severe disease, and may be useful for predicting disease progression. Patients with elevated C-reactive protein at the time of initial presentation were more likely to have acute kidney injury, venous thromboembolism, critical illness, and in-hospital mortality during their hospital stay compared with patients with lower levels.

8. Serum erythrocyte sedimentation rate

9. Serum lactate dehydrogenase (LDH)

Elevated serum lactate dehydrogenase is significantly associated with severe disease, and may be useful for predicting disease progression. The lactate dehydrogenase (LDH) test looks for signs of damage to the body's tissues. LDH is an enzyme found in almost every cell of your body, including your blood, muscles, brain, kidneys, and pancreas. The enzyme turns sugar into energy. The LDH test measures the amount of LDH in your blood or other body fluid.

High levels of LDH indicate some form of tissue damage. High levels of more than one isoenzyme may indicate more than one cause of tissue damage. For example, a patient with pneumonia could also have a heart attack. Extremely high levels of LDH could indicate severe disease or multiple organ failure.

10. Serum interleukin-6 level

Elevated interleukin-6 level is significantly associated with severe disease, and may be useful for predicting disease progression.  IL-6 is released by monocytes and macrophages in response to other inflammatory cytokines which include IL-11 and tumor necrosis factor (TNF)-beta. The IL-6 receptor is present on normal T-lymphocytes in the resting phase, normally activated B-cells, and cells in the myeloid and hepatic cell lines. IL-6 is also found on B cells modified by the Epstein-Barr virus.

Level of IL-6 predicts respiratory failure in hospitalized symptomatic COVID-19

11. Serum procalcitonin

Elevated serum procalcitonin is significantly associated with severe disease, and may be useful for predicting disease progression.

12.  Serum ferritin level

Potential role of ferritin during inflammation following COVID-19 infection. Active ferritin production by macrophages and cytokines may lead to hyper-ferritinemia, which in turn, might promote the production of several pro-inflammatory (IL-1β) and anti-inflammatory cytokines (IL-10),.

Ferritin is a blood protein that contains iron. A ferritin test helps your doctor understand how much iron your body stores. If a ferritin test reveals that your blood ferritin level is lower than normal, it indicates your body's iron stores are low and you have iron deficiency. As a result, you could be anemic.

Normal serum ferritin levels vary between laboratories but generally concentrations >300 µg/L in men and postmenopausal women and >200 µg/L in premenopausal women are regarded as elevated.

If a ferritin test shows higher than normal levels, it could indicate that you have a condition that causes your body to store too much iron. It could also point to liver disease, rheumatoid arthritis, other inflammatory conditions or hyperthyroidism. Some types of cancer also can cause your blood ferritin level to be high.

13.  Serum amyloid A level

Amyloid A blood testing can be used to monitor treatment of inflammation in amyloidosis. Background: The term amyloidosis describes a group of disorders caused by abnormal folding, aggregation and accumulation of certain proteins in the tissues, in an abnormal form known as amyloid deposits. Elevated ferritin is significantly associated with severe disease, and may be useful for predicting disease progression.

14. serum creatine kinase and myoglobin

Elevated serum creatine kinase and myoglobin are significantly associated with severe disease, and may be useful for predicting disease progression. Levels increase in severe disease; therefore, it may be useful as a biomarker for predicting disease progression.

15.  Blood and sputum cultures

Collect blood and sputum specimens for culture in patients with severe or critical disease to rule out other causes of lower respiratory tract infection and sepsis, especially patients with an atypical epidemiologic history.

16.  Chest x-ray

Investigations to consider

17.   Computed tomography (CT) chest

CT scan generally shows an increase in the size, number, and density of ground-glass opacities in the early follow-ups period, with a progression to mixed areas of ground-glass opacities, consolidations, and crazy paving peaking at day 10 to 11, before gradually resolving or persisting as patchy fibrosis.

Serology

18.  Antigen test

Emerging tests

19.  Reverse transcription loop-mediated isothermal amplification (RT-LAMP)

An at-home test kit that provides rapid results within 30 minutes has been approved in the US under an emergency-use authorization for self-testing at home that provides rapid results.

20.  Lung ultrasound

21.  Calprotectin

Calprotectin is an emerging biomarker of interest. Calprotectin levels often increase following infection or trauma, and in inflammatory disease. Serum/fecal calprotectin levels have been demonstrated to be significantly elevated in COVID-19 patients with severe disease, and it may have prognostic significance.