Diagnostic accuracy of two point‐of‐care kits for the diagnosis of Giardia species infection in dogs

Costa, M.; Clarke, C.; Mitchell, S.; Papasouliotis, K.

OBJECTIVES: The objective of this study was to compare results obtained by ZnSO(4) Flotation and SNAP (®)Giardia to those generated by the new point‐of‐care tests Single and Triple Rapid. METHODS: Prospective study evaluating 51 canine faecal samples submitted at a reference laboratory for the presence of Giardia spp. Kappa statistics, specificity, sensitivity, positive predictive value (PPV) and negative predictive value (NPV) were calculated by comparing the new tests to the combined results of ZnSO(4) and SNAP tests. RESULTS: There was fair (Single Rapid, j=0·434) to good (Triple Rapid, j =0·797) agreement with the reference tests. At this study's prevalence (59 to 61%), specificities and PPV were high (1·00) with both Rapid tests, but sensitivities and NPV were lower for the Single than for the Triple (0·48 vs 0·83 and 0·55 vs 0·80) tests. At lower prevalence rates, both tests exhibited a high PPV (1·00), but the NPV were higher with the Triple (0·96 to 0·99) than the Single (0·88 to 0·96) Rapid test. CLINICAL SIGNIFICANCE: Both tests exhibited excellent PPV values at all prevalence rates but an excellent NPV only at low prevalence. As the prevalence is likely to be low (<15%) in clinical settings, we propose that these tests may be helpful in the in‐house diagnosis of Giardia spp infection. However, they exhibit lower sensitivity than the combined sensitivity of ZnSO(4) and SNAP tests, particularly in high prevalence settings.