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

Rapid on-site diagnosis of canine giardiosis: time versus performance

BACKGROUND

Infections by protozoans of the genus Giardia are a common cause of diarrhea in dogs. Canine giardiosis constitutes a disease with a zoonotic potential; however, it is often underestimated due to its challenging diagnosis. The objective of the study was to assess the diagnostic performance of an immunochromatographic strip test (SpeedTM Giardia, Virbac, France) comparing it with microscopy (zinc sulfate flotation) by utilizing the combination of an enzyme immunoassay (ProSpecTTM Giardia EZ Microplate Assay, Oxoid Ltd., UK) and the PCR as the gold standard. A positive result in both ELISA and PCR was set as the gold standard.

METHODS

Initially, fecal samples from dogs with clinical signs compatible with giardiosis were tested with the SpeedTM Giardia test and separated into two groups of 50 samples each: group A (positive) and group B (negative). Thereafter, all samples were examined by zinc sulfate centrifugal flotation technique and assayed by the ProSpecTTM Giardia Microplate Assay and PCR. The performance of the SpeedTM Giardia and zinc sulfate centrifugal flotation tests were calculated estimating sensitivity, specificity, and positive and negative likelihood ratio; the chi-square and McNemar tests were used for the comparison of the two methods.

RESULTS

Giardia cysts were not detected by microscopy in 16 out of the 50 samples (32%) of group A and in none of group B samples. Eight out of 50 samples in group B (16%) were tested positive both with the ProSpecTTM Giardia Microplate Assay and PCR. Fecal examination with the SpeedTM Giardia test was more sensitive (86.2%) than the parasitological method (58.6%, P < 0.001) while the specificity of both methods was 100%.

CONCLUSIONS

The SpeedTM Giardia test is an easy-to-perform diagnostic method for the detection of Giardia spp., which can increase laboratory efficiency by reducing time and cost and decrease underdiagnosis of Giardia spp. infections. This immunochromatographic strip test may be routinely exploited when a rapid and reliable diagnosis is required, other diagnostic techniques are unavailable and microscopy expertise is inefficient. In negative dogs with compatible clinical signs of giardiosis, it is recommended either to repeat the exam or proceed with further ELISA and PCR testing.

Prevalence of Giardia duodenalis infection, co-morbidities and associated risk factors in dogs admitted to a veterinary teaching hospital in Israel

Giardia duodenalis causes gastro-intestinal (GI) disease and carries a zoonotic risk. The risk for infection depends on local prevalence and individual immunity, but clinical signs are inconsistent and the role of G. duodenalis in other GI diseases is unknown. The current study aims were to evaluate the prevalence of G. duodenalis in dogs presented to a university veterinary teaching hospital in Israel, investigate risk factors for infection and its associations with other diseases. Fecal samples from 163 dogs were tested for G. duodenalis by an antigen assay (FASTest® Giardia strip). Prevalence of G. duodenalis infection was 11.9 %. It was significantly associated with young age (≤1year) and canine parvoviral enteritis. Housing conditions, signs of GI disease or other systemic diseases were unassociated with infection. In conclusion, G. duodenalis infection prevalence is relatively low in the study population. Young age and diagnosis of co-infections are common, warranting screening for G. duodenalis.

Comparative cost-effectiveness of immunoassays and FLOTAC for diagnosing Giardia spp. infection in dogs

BACKGROUND

Giardia spp. is a protozoan pathogen and is the most common enteric parasite of domestic animals and humans. Assays for detecting infection in fecal samples using direct or indirect examinations are important tools for diagnosing the disease. The objective of the present study was to compare the cost-effectiveness of immunoassays and FLOTAC technique for diagnosing Giardia spp. infection in dogs.

RESULTS

Fecal samples from 80 positive stray dogs were tested for the presence of copro-antigens of Giardia spp. using the direct immunofluorescence assay (IFA), a rapid enzyme-linked immunosorbent assay (ELISA) and the FLOTAC double technique. All methods were performed in accordance with the instructions reported in the original description for each technique. The results showed that ELISA can be run in less time than IFA and almost at the same time of the FLOTAC technique. Among the tests used in this study, FLOTAC had the lowest cost per correct diagnosis, compared with immunoassays.

CONCLUSIONS

The results from this cost-effectiveness analysis, in combination with the sensitivity and specificity of the FLOTAC technique, suggest that the FLOTAC technique can be use in the routine diagnosis of Giardia spp. infection in dogs.

Comparative performance of reference laboratory tests and in-clinic tests for Giardia in canine feces

BACKGROUND

We examined the performance of four in-clinic Giardia diagnostic tests by comparing results to three laboratory methods for detection of Giardia. A set of 177 fecal samples originally submitted to a commercial laboratory by veterinarians for routine ova and parasite (O&P) testing was used. Specimens were examined by direct immunofluorescence assay (DFA) for presence of Giardia cysts which served as the gold standard. Fecal samples were tested using a Giardia-specific cyst wall antigen microtiter plate format enzyme-linked immunosorbent assay (ELISA) and each of the in-clinic assays adhering to the package insert for each kit.

RESULTS

Evaluated were four in-clinic antigen test kits: VetScan® Canine Giardia Rapid Test (Abaxis), Anigen® Rapid CPV-CCV-Giardia Antigen Test (BioNote), SNAP® Giardia Test (IDEXX) and Witness® Giardia Test (Zoetis). In the comparison of the in-clinic tests to the DFA standard test sensitivity ranged between 70.0-87.1%, and specificity ranged between 71.1-93.4%.

CONCLUSION

Of the tests evaluated here, the SNAP test had the highest sensitivity and specificity. The SNAP test had the highest percent positive and percent negative agreement when compared to the microtiter plate format ELISA and the O&P assay.