Paper II — 2024 March (Supplementary) (2010 Scheme) — Q3
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Paper II
2024 March (Supplementary) (2010 Scheme) · 40 marks · 120 min
Question
Laboratory diagnosis of falciparum Malaria.
Q35 marksShort Essays
Answer
Laboratory diagnosis of Plasmodium falciparum malaria:
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 (since these sequester in deep vessels via PfEMP1-mediated cytoadherence), and characteristic crescent/banana-shaped gametocytes.
QBC (Quantitative Buffy Coat) method — fluorescence-based concentration technique, more sensitive than routine smear but does not allow precise species identification.
PCR — highly sensitive/specific, useful for low-level or mixed infections.
Serology — detects past exposure, not useful for acute diagnosis.
Practical note: since mature parasite stages sequester in deep vessels, peripheral smears in falciparum malaria show predominantly early ring forms, and a very high or rapidly rising parasitaemia in peripheral blood is itself a marker of severity.
