Table 1.

Classifications for disease severity.

The National Institutes of Health (NIH) classification
1) Asymptomatic or presymptomatic infection	Positive test for SARS-CoV-2 but no symptoms
2) Mild illness	Any signs and symptoms (e.g., fever, cough, sore throat, malaise, headache, muscle pain) without shortness of breath, dyspnea, or abnormal chest imaging
3) Moderate illness	Evidence of lower respiratory disease by clinical assessment or imaging and a saturation of oxygen (SaO2) ≥ 94% on room air at sea level
4) Severe illness	Respiratory frequency >30 breaths per minute, SaO2 < 94% on room air at sea level, ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO2/FiO2) < 300, or lung infiltrates > 50%
5) Critical illness	Respiratory failure, septic shock, and/or multiple organ dysfunction
Wu classification
1) Mild illness	No or mild symptoms (fever, fatigue, cough, and/or less common features of COVID-19)
2) Severe illness	Tachypnea (respiratory rate >30 breaths per minute), hypoxia (oxygen saturation ≤ 93% on room air or PaO2/FiO2 < 300 mmHg), or >50% lung involvement on imaging)
3) Critical illness	Cases with severe clinical features like respiratory failure, shock, or multiorgan dysfunction
The National Guideline by Turkish Ministry of Health, General Directorate of Public Health
1) Uncomplicated cases	a) Symptoms such as fever, muscle/joint pain, cough, sore throat, and respiration without distress (respiratory rate < 24, SpO2 > 93% on room air)ANDb) Patients with normal chest X-ray and/or lung tomography
2) Cases with mild/moderate pneumonia	a) Symptoms such as fever, muscle/joint pain, cough and sore throat, respiratory rate < 30/min, SpO2 > 90% on room airANDb) Mild-to-moderate pneumonia in chest radiography or tomography
3) Cases with severe pneumonia	a) Symptoms such as fever, muscle/joint pain, cough and sore throat, tachypnea (30/min), SpO2 below 90% on room airANDb) Bilateral diffuse pneumonia finding on chest radiography or tomography
4) Critical cases that may necessitate intensive care unit admission	Cases with at least one of the following clinical findings:a) Dyspnea and respiratory distressb) Respiratory rate ≥ 30/minc) PaO2/FiO2 < 300d) SpO2 < 90% or PaO2 < 70 mmHg despite 5 L/min oxygen therapye) Hypotension (systolic blood pressure < 90 mmHg and 40 mmHg from usual SBP and mean arterial pressure < 65 mmHg, tachycardia > 100/minf) Acute kidney injury, abnormal liver function test, development of acute organ dysfunction such as confusion, acute bleeding diathesis, and patients with immunosuppressiong) High troponin levels and arrhythmiah) Lactate > 2 mmoli) Skin disorders such as capillary return disorder and cutis marmaratus

COVID-19: Coronavirus disease 2019, SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2