IDEXX SNAP 4Dx Plus Test provides sensitive and specific detection of heartworm and tick-borne diseases Significant performance differences between the Abaxis VetScan FLEX4 Rapid Test and the IDEXX SNAP 4Dx Plus Test could have clinically relevant consequences Introduction Since 2001, IDEXX has been a world leader in tick-borne disease testing by offering generations of high-quality, multiplexed diagnostic products (SNAP® 3Dx® Test, SNAP® 4Dx® Test, and SNAP® 4Dx® Plus Test). The latest version, the SNAP 4Dx Plus Test, detects, in addition to heartworm antigen, antibodies to five pathogens, which include A. phagocytophilum, A. platys, B. burgdorferi (Lyme), E. canis, and E. ewingii. Its accurate performance has been documented in large-population studies around the globe.1–3 Recently, Abaxis introduced the VetScan® FLEX4 Rapid Test with product claims similar to the SNAP 4Dx Plus Test. IDEXX conducted a study to compare the performance of this new test with the SNAP 4Dx Plus Test for the detection of heartworm and tick-borne diseases, using a scientifically rigorous methodology in a broad population of field samples. SNAP 4Dx Plus Test VetScan FLEX4 Rapid Test Study design Canine samples were sourced from worldwide commercial reference laboratories (IDEXX Reference Laboratories) and veterinary clinics. They were positive by reference methods (see table 1) that included immunofluorescence assay (IFA), Western blot, PetChek® Heartworm PF Antigen Test (ELISA), and necropsy. These samples were further characterized based on geographic distribution of tick-borne diseases and species-specific ELISA.4,5 Species-specific ELISA was necessary, particularly to differentiate Ehrlichia species that overlap in geographic distributions. To further enhance monospecific identification of E. canis samples, clinical submissions were used from dogs in Germany and southern Europe where E. ewingii and its competent tick vectors have not been reported. Reference method Further characterization method Negative = PetChek Heartworm PF Antigen Test Western blot Geography, species-specific ELISA Species-specific ELISA Table 1. Sample set and reference methods. Samples were tested, in a blinded and randomized manner, on the VetScan FLEX4 Rapid Test and the SNAP 4Dx Plus Test following manufacturers’ instructions. The test results were compared to reference method results for calculation of sensitivity and spe

Conclusion For all vector-borne infections evaluated in this study, the IDEXX SNAP® 4Dx® Plus Test was meaningfully more accurate than the Abaxis VetScan® FLEX4 Rapid Test. Because the consequences of missing a heartworm infection are substantial, of particular note is the relatively low sensitivity of 88.2% on heartworm for the VetScan FLEX4 Rapid Test (see figure 1). SNAP 4Dx Plus Test Figure 1. Sensitivity vs. gold-standard reference methods. This study revealed the sensitivity limitations of the VetScan FLEX4 Rapid Test and showed its performance to be similar to or worse than that of Abaxis...