Table 10.9-1. Laboratory and clinical criteria used for epidemiologic and research reasons to define for severe falciparum malariaa (WHO 2021)

Symptoms or syndromes


Impaired consciousness

In adults: GCS score <11


Generalized weakness: inability to sit, stand, or walk without assistance


Multiple convulsions

>2 episodes within 24 h


Severe anemia

Hematocrit <20% or blood hemoglobin <7 g/dL with concurrent parasitemia >10,000/microL


Serum bilirubin >3.0 mg/dL (> 50 micromol/L) with concurrent parasitemia >100,000/microL

Acute kidney injury

Serum creatinine >3.0 mg/dL (265 micromol/L) or BUN >20 mmol/L

Pulmonary edema or acute respiratory failure

Pulmonary edema confirmed by radiography or arterial oxygen saturation <92% on room air, with respiratory rate >30/min, often paradoxical movements of the chest and crepitus on auscultation


Serum glucose <40 mg/dL (2.2 mmol/L)


Compensated: capillary refill time >3 s or cold distal parts of lower limbs

Decompensated: systolic arterial pressure <80 mm Hg with evidence of impaired perfusion


Gum bleeding, epistaxis, GI bleeding


Parasitemia >10% in endemic countries; in nonendemic countries, >5% is considered as severe malaria


Base deficit >8 mEq/L or serum HCO3 <15 mmol/L or lactic acid >5 mmol/L

a Severe P vivax malaria is defined as P falciparum malaria but with no parasite density thresholds.

Severe P knowlesi malaria is defined as P falciparum malaria, with 2 differences:

– P knowlesi hyperparasitemia: Parasite density >100,000/microL.

– Jaundice and parasite density: >20,000/microL.

Adapted from 2021 World Health Organization guidelines.

BUN, blood urea nitrogen; GCS, Glasgow Coma Scale; GI, gastrointestinal; WHO, World Health Organization.