Comparison of 4 Giardia diagnostic tests in diagnosis of naturally acquired canine chronic subclinical giardiasis.
BACKGROUND
The performance of Giardia diagnostic tests that detect either cysts or fecal antigens has not been thoroughly examined.


OBJECTIVE
We examined the concordance and agreement among 4 Giardia diagnostic tests (2 cyst and 2 coproantigen detection methods) in a colony of dogs chronically and subclinically infected with Giardia.


METHODS
Twenty dogs with chronic, subclinical Giardia infection.


METHODS
Giardia diagnostic tests were performed repeatedly on each dog over 120 days. Fecal cyst detection methods (ZnSO4 flotation and fluorescent antibody [FAB] coproscopy) were performed 3 times per week. Coproantigen methods (Giardia SNAP test and quantitative ELISA) were performed weekly. Results were analyzed and compared among methods.


RESULTS
When compared with FAB coproscopy, all of the in-house diagnostic tests had excellent positive predictive values (PPVs, 95-99%) at the study prevalence (89%). At lower prevalence rates, ZnSO4, SNAP, and ELISA tests all had good negative predictive values (NPVs), but poor PPVs. There was poor to good agreement among tests by kappa analysis.


CONCLUSIONS
Our findings show that most commonly used in-house Giardia diagnostic tests have poor agreement with the gold standard method (FAB coproscopy). The in-house tests have good NPVs, but poor PPVs, at prevalence rates common in most clinical settings.
Rishniw
M
M
Department of Clinical Sciences, VMC 2001, College of Veterinary Medicine, Cornell University, Ithaca, NY 14850, USA.
Liotta
J
J
Bellosa
M
M
Bowman
D
D
Simpson
K W
KW
D000818:Animals; D000953:Antigens, Protozoan; D004283:Dog Diseases / Q000175:diagnosis* / Q000469:parasitology; D004285:Dogs; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005243:Feces / Q000469:parasitology; D005260:Female; D005872:Giardia / Q000302:isolation & purification*; D005873:Giardiasis / Q000175:diagnosis / Q000662:veterinary*; D008297:Male; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic / Q000662:veterinary; D012680:Sensitivity and Specificity; D019287:Zinc Sulfate
D000953:Antigens, Protozoan; D011933:Reagent Kits, Diagnostic; D019287:Zinc Sulfate