Giardia Test: IDEXX SNAP

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

Purpose

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

Principle

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.

Procedure

  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.

Benefits

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.

Problems

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 ZnSO 4 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.

References

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.