Intestinal parasites (threadworms, giardiasis, taeniasis…): which test?

• Worms seen on the anal margin or in the stool: diagnosis made, no tests.

Parasitological examination

• Anal adhesive tape test (in the morning, before passing stool and washing)

Stool tests (recently passed stool)

• Stool parasitology (state: travel, eosinophilia, immunosuppression)
• Cryptosporidium testing (immunosuppression; to be requested explicitly)if neededImmunosuppression ^[6]; procedure distinct from the standard parasitological examination, to be prescribed explicitly ^[3].
• Search for Strongyloides larvae (Baermann technique) (stay in a tropical area)if neededStay in or origin from an endemic area, eosinophilia: standard examination poorly sensitive for Strongyloides ^[7]; the NABM leaves the Baermann technique to the laboratory’s initiative according to geographical history, hence the mention of the stay ^[3].
• Giardia antigen or PCR in stool (if giardiasis suspected and parasitological examination negative)if needednon-French guidelineIn the United Kingdom, the BSG retains stool ELISA when persistent giardiasis is in doubt (sensitivity 92%, specificity 98%) ^[8]; an American review judges the antigen test more sensitive than the parasitological examination ^[9]; in the Netherlands, nucleic acid amplification is the reference method ^[10]. In France, these tests have no NABM procedure, and the parasitological examination remains the reference ^[3].

Laboratory tests

• FBC (looking for eosinophilia if helminthiasis suspected)if neededSuspected helminthiasis (chronic strongyloidiasis: moderate eosinophilia or raised IgE in up to 75% of cases) ^[7]; eosinophilia directs the parasitological examination ^[3]. See the page “Hypereosinophilia”.