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Friday, October 29, 2010

MRCP Part 1 MCQ question #24

A young girl returns from a trip to India with a protracted history of watery diarrhoea.
Giardiasis is suspected but three stool samples are negative.
What is the best investigation to confirm Giardia as a diagnosis?

a) CT abdomen
b) Rectal biopsy
c) Serum IgM Giardia antibodies
d) Small intestine biopsy
e) Stool microscopy

Answer
d) Small intestine biopsy

Explanation:
Giardia may be difficult to diagnose from stool samples alone. Concentration techniques and optimising sample preparation may improve stool sample yield.

However, parasitic antigen detection in stool is at least as sensitive and specific as good microscopic examination of stool, and maybe easier to perform.

In this case detection of Giardia may be achieved by sampling of duodenal fluid, or small bowel biopsy.