Add a note on lab diagnosis of Pernicious Malaria.
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Answer
Pernicious malaria refers to severe, life-threatening malaria caused by Plasmodium falciparum, characterized by cerebral involvement, severe anaemia, and multiorgan complications from cytoadherence/sequestration of parasitized RBCs.
Laboratory diagnosis:
Peripheral blood smear microscopy — gold standard; thick smear for screening/detecting low parasitaemia, thin smear for species identification and quantifying parasitaemia (Giemsa stain). P. falciparum is identified by delicate ring forms (often with double chromatin dots, multiple rings per cell), absence of larger trophozoite/schizont stages in peripheral blood (sequestration in deep vessels via PfEMP1-mediated cytoadherence), and characteristic crescent/banana-shaped gametocytes; a very high parasitaemia (e.g., >5%) itself indicates severe disease.
Rapid diagnostic tests (RDTs) — HRP-2 (P. falciparum-specific) antigen detection, useful for rapid confirmation in emergency settings.
QBC method — fluorescence-based concentration technique, more sensitive than routine smear.
PCR — highly sensitive/specific, useful for confirming low-level infection.
Supportive laboratory findings for severity assessment: full blood count (severe anaemia, thrombocytopenia), renal function tests (acute kidney injury), blood glucose (hypoglycaemia), liver function tests, blood gas/lactate (metabolic acidosis in severe disease), and coagulation profile (DIC in severe cases) — all important for assessing and monitoring the multiorgan complications of pernicious/severe falciparum malaria.
Serology — detects past exposure, not useful for acute diagnosis.
