Evaluation of urine for Dirofilaria immitis antigen detection in dogs

Abstract

Background Infection by the canine heartworm, Dirofilaria immitis, causes a potentially fatal, multisystemic disease in dogs. Diagnosis of D. immitis relies on serologic antigen detection coupled with microfilariae identification. It has been shown that immune-complex dissociation (ICD) of serum/plasma by heat treatment increases detection of infection, especially in dogs from endemic areas and with inconsistent use of heartworm prevention. The aim of this study was to assess the use of urine for heartworm antigen detection in dogs using a commercial ELISA (DiroCHEK®). Methods Matching serum/plasma and urine of 29 experimentally infected dogs at different time points post-infection were tested to assess the feasibility of antigen detection in urine. Matching serum and urine samples of 267 dogs admitted to a spay/neuter clinic with unknown infection status were also evaluated for antigen detection. Results In the experimental samples, antigenemia was detected in 86.2% and 90.9% of samples pre- and post-ICD, respectively, while antigenuria was detected in 75.9% and 72.4% of samples pre- and post-ICD, respectively. In the clinic samples, antigenemia was detected in 7.9% of dogs pre-ICD and 12.4% post-ICD, while antigenuria was detected in 11.6% and 6.4% of dogs pre- and post-ICD, respectively. In experimental samples, sensitivity (SEN), specificity (SPE), and positive predictive value (PPV) of antigenuria were high (85%, 100%, 100%, respectively). In clinic samples, SPE and negative predictive value (NPV) were high (95% and 92%, respectively). In contrast, NPV in experimental samples (40%), and SEN and PPV in clinic samples (58% and 61%, respectively) were low. Overall kappa agreement between antigenemia and antigenuria was fair to moderate. Conclusion These data suggest that urine might be a useful and less invasive biofluid for heartworm antigen detection in dogs.