Diagnosis of Giardiasis

The diagnosis of giardiasis can be done with the help of-

Stool examination-

• Microscopic examination of stool for cysts- The most common way to diagnose giardiasis is by the visualization of the Giardia cysts in the stool sample. Cysts are excreted at intervals and so it requires examination of at least three-stool specimen for correct diagnosis.
• Antigen assay of stool- Presence of Giardia antigen in the feces is detected using Counter Current Immuno-Electrophoresis (CIEP) or Enzyme Linked Immunosorbent Assay (ELISA) technique.

Examination of the duodenal contents-

Microscopic examination of duodenal contents is carried out when repeated stool examination is negative but giardiasis is still suspected. The methods followed to collect duodenal contents are-

• String test- The patient swallows a gelatin capsule which is attached to a nylon string; the free end of the string is fixed in the mouth. The capsule dissolves in the stomach and the lower end of the string remains in the duodenum and jejunum. After overnight incubation, the string is removed and the bile stained mucus is collected on a glass slide and examined microscopically to look for the trophozoite stage of the parasite.
• Duodenal aspiration- The duodenal contents (contents of the first part of the intestines) are aspirated to demonstrate the presence of trophozoites.