2.6 Operational definitions
According to the provisional guidelines of the NIH Pakistan,14 following definitions were employed in the study.
Moderate Disease: Patients diagnosed with COVID-19 infection with any one of the following features:
  1. Respiratory rate ≥ 30/min at rest.
  2. Oxygen saturation (SpO2) ≤ 93% on room air.
  3. Arterial oxygen partial pressure (PaO2) /oxygen uptake concentration (FiO2) ≤ 300.
Severe Disease: Patients with moderate disease criteria plus any one of the following:
  1. Oxygen requirement of more than 10 liters for 90% saturation.
  2. 50% of lung involvement on either chest X-ray or HRCT.
  3. CRP > 10 mg/L, D-dimer > 1000 mg/mL, serum ferritin > 1000 ng/mL.
  4. Secondary infection (diagnosed by blood culture and sensitivity test or raised procalcitonin).
  5. Arterial oxygen partial pressure (PaO2)/oxygen uptake concentration (FiO2) [PaO2/FiO2] (PF ratio) < 118 mmHg.
Critical Disease: Patients with severe disease and any one of the following were labeled as having critical disease:
  1. Shock
  2. Acute Respiratory Distress Syndrome (ARDS)
  3. Cardiac injury
  4. Multi-organ dysfunction
Shock: Persistent hypotension despite volume resuscitation, requiring vasopressor to maintain mean arterial pressure (MAP) ± 65 mmHg and serum lactate level > 2 mmol/L.15
ARDS: As per the Berlin Definition of ARDS:16
  1. Onset: Within one week of a known clinical consultation.
  2. Respiratory failure not fully explained by cardiac failure or fluid overload.
  3. Bilateral opacities not fully explained by fluid overload, lobar or lung collapse or nodules.
  4. Oxygen impairment with PF ratio < 300 mmHg.
Cardiac Injury: Cardiac injury is diagnosed if the serum level of a cardiac marker (such as high-sensitivity troponin I) is higher than the 99th percentile upper reference limit, or the ECG and echocardiogram show new abnormalities.17
Multi-organ Dysfunction: Acute life-threatening organ dysfunction with any of the following signs:
  1. Altered mental status
  2. Reduced urine output
  3. Shortness of breath or increased respiratory failure
  4. Signs of impending shock or circulatory failure
  5. Decrease oxygen saturation
  6. Lab evidence of coagulopathy
  7. Thrombocytopenia
  8. Acidosis
  9. Raised lactate level
  10. Deranged liver function and renal function