Giardia Test: IDEXX SNAP

This test is applied to the feces to detect antigen produced by Giardia spp.

The IDEXX SNAP® Giardia Test is a coproantigen detection test that uses enzyme-linked immunosorbent assay (ELISA) technology. The well in the snap test is coated with antibodies specific to Giardia antigen, so when the fecal sample used contains Giardia antigen it returns a positive result. See https://ca.idexx.com/en-ca/veterinary/support/documents-resources/snap-giardia-test-resources/ for more details.

1. Using SNAP® Giardia Test Conjugate/Swab device swab fecal sample and place swab tip into tube.
2. Bend bulb to break seal and release conjugate.
3. Squeeze and release bulb 3 times to mix sample and conjugate.
4. Squeeze bulb to dispense 5 drops into the sample well of the SNAP® device.
5. When colour first appears in the activation circle, press firmly to activate (you will hear a distinctive “snap”.
6. Read the test results 8 minutes from the time of activation.
7. A blue dot = positive (any colour development in the sample spot indicates a positive result).

 

NOTE: it is critical that these directions are followed carefully.

 

This test is very convenient for in-clinic use since it is quick, cost effective, accurate and doesn’t require any skill in parasite identification. The test has a sensitivity of 95% and a specificity 99% (Rishniw M et al 2010). It has greater accuracy than fecal flotations or direct smears. It is better than zinc sulfate fecal floats which requires three consecutive repetitions to obtain a sensitivity as high as the SNAP® Giardia Test. Also, Giardia cysts are small and in smears can be confused with pollen.

 

Fluorescent antibody (FAB) coproscopy is considered the gold standard for the diagnosis of Giardia. A study by M. Rishniw et al. comparing four Giardia diagnostics tests determined that most of the commonly used in-clinic Giardia diagnostic tests used, including ZnSO₄ flotations, quantitative ELISA and the Giardia SNAP® test, have good negative predictive values but poor positive predictive values at the prevalence levels in most clinical settings, and had insufficient agreement with the gold standard FAB coproscopy technique.

Rishniw M et al (2010) Comparison of 4 Giardia Diagnostic Tests in Diagnosis of Naturally Acquired Canine Chronic Subclinical Giardiasis. Journal of Veterinary Internal Medicine 24:293-297.