Comparison of Three Rapid Commercial Canine Parvovirus Antigen Detection Tests with Quantitative Polymerase Chain Reaction (qPCR)

Objective and hypothesis: To evaluate the effectiveness of three commercial ELISA rapid tests in comparison with qPCR for the diagnosis of canine parvovirus infection using fecal samples. It was hypothesized that the ELISA rapid tests evaluated in this study are as effective as qPCR method in diagnosis of canine parvovirus infection in fecal samples. Background: Canine parvovirus-2 (CPV-2) infection is an acute, life-threatening, and highly contagious viral disease. The infected dogs shed virus in their stool and a variety of diagnostic methods have been developed for the diagnosis of the infection using fecal samples. Rapid ELISA tests are commonly used in veterinary practices. However, the accuracy of the results of rapid tests has been questioned in many reports and a low sensitivity has been reported for these tests. Methods: The effectiveness of three parvovirus commercial ELISA rapid tests (Zoetis, Abaxis, and IDEXX) was compared with the laboratory method, qPCR, as a quantitative assay with high sensitivity and specificity. Using qPCR provides information on the amount of viral antigen. Fecal samples from 80 dogs suspected of having CPV-2 infection, based on the clinical signs, were tested by the three ELISA rapid tests and qPCR method for the presence of canine parvovirus antigen. Specificity, sensitivity, positive, and negative predictive values (PPV and NPV) for all tests were calculated and compared. Results: A total of 42 samples were qualified for testing based on the inclusion criteria. The results of qPCR indicated 22 positive samples; however, only 10 of those samples were diagnosed as positive when ELISA kits were used. There was no difference between the results of the three ELISA tests from different manufacturers included in the study. The ct-values for the qPCR tests ranged from 12.03 to 34.21. The ct- values for the samples that were found as false negatives when ELISA tests were used ranged from 21.12 to 34.21. The sensitivity and specificity of the ELISA tests were 45.4% and 100% respectively versus 100% sensitivity and specificity for the qPCR method. The PPV and NPV values for ELISA tests were 100% and 62.5%, respectively. Conclusion: ELISA rapid tests are associated with a low sensitivity and therefore, the negative results should be confirmed using PCR technology to confirm the diagnosis.