Performance of SNAP® 4Dx® Plus and AccuPlex™4 in Dogs with different Heartworm Burdens

SNAP (R) 4Dx (R) Plus (IDEXX Laboratories, Westbrook, ME) is a commercially available in-ofice test kit for the simultaneous detection of Diroilaria immitis antigen and antibodies to Anaplasma phagocytophilum, A. platys, Borrelia burgdorferi, Ehrlichia canis, and E. ewingii in blood, plasma, or serum of dogs. AccuPlex (TM) 4 test (ANTECH Diagnostics (R), Irvine, CA) is a recently launched reference laboratory test that detects heartworm antigen and antibodies to Lyme disease, anaplasmosis, and ehrlichiosis in dogs. In this report, we compared the performance of SNAP (R) 4Dx (R) Plus and AccuPlex (TM) 4 for detection of heartworm antigen in sera from dogs having necropsy-conirmed infections with a broad range of worm burdens. A total of 72 necropsy conirmed samples with a wide range of worm burden and 21 negative samples conirmed negative by PetChek (R) Heartworm PF Antigen Test (IDEXX Laboratories, Westbrook, ME) were used in this evaluation. Of the 72 necropsy-conirmed samples, SNAP (R) 4Dx (R) Plus test detected 65 samples compared to 54 samples detected by AccuPlex (TM) 4 assay. The AccuPlex (TM) 4 assay reported a positive result for one antigen negative sample. For the low-worm burden populations, SNAP (R) 4Dx (R) Plus detected 82% of dogs with one worm and 100% of dogs with two worms, while AccuPlex (TM) 4 only detected 53% of dogs with one worm and 86% of dogs with two worms, respectively. In this study, where a direct comparison of the test methodologies was performed using the same sample set, the results indicate that SNAP (R) 4Dx (R) Plus is more sensitive than AccuPlex (TM) 4 in detecting heartworm antigen in dogs with low worm burdens.