Paper II — 2021 February (Supplementary) (2010 Scheme) — Q3
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Paper II
2021 February (Supplementary) (2010 Scheme) · 40 marks · 120 min
Question
Laboratory diagnosis of malaria
Q35 marksShort Essays
Answer
Laboratory diagnosis of malaria (Plasmodium species):
Peripheral blood smear microscopy — the gold standard; thick smear for screening/detecting low parasitaemia, thin smear for species identification and quantifying parasitaemia (Giemsa staining), ideally taken during/soon after a febrile episode.
Rapid diagnostic tests (RDTs) — immunochromatographic tests detecting P. falciparum-specific histidine-rich protein-2 (HRP-2) or pan-species lactate dehydrogenase/aldolase antigens; rapid, useful in field settings without microscopy access.
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 detecting low-level or mixed infections.
Serology — detects past exposure, not useful for diagnosing acute infection.
Key species-identification features: P. falciparum — delicate ring forms (multiple rings/cell, double chromatin dots), absence of larger stages in peripheral blood (sequestration), crescent-shaped gametocytes; P. vivax — amoeboid trophozoites, Schüffner’s dots, enlarged infected RBCs; P. malariae — band-form trophozoites, “rosette” schizonts; P. ovale — oval, fimbriated RBCs.
