Evaluation of the performance of heartworm antigen test kits and heartworm antibody test kits for the diagnosis of the infection in dogs and cats

A controlled study (negative and positive controls) and a field study were carried out on canine and feline serum samples to assess the diagnostic value of antigen and antibody in-clinic test kits for the diagnosis of heartworm infection. Overall 384 canine serum samples have been examined by 3 antigen tests (Witness Dirofilaria, Snap HTWM e Speed Diro) in comparison with antigen PetChek HTWM following the laboratory protocol, assumed as gold standard. One hundred seventy height feline serum samples have been examined by Witness, Snap antigen kits and HESKA antibody in cats experimentally infected and PetChek positive and/or with worms visualized by echocardiography. In the dog, the specificity of antigen kits was 100% and the sensitivity was 92%, 98% and 59% for Witness, Snap and Speed, respectively (Witness vs Snap p>0.05, both kit vs Speed p<0.001). The positive predictive value was 100% for all the kits; the negative predictive values were 97%, 98% and 87% for or Witness, Snap and Speed, respectively. In the cat, Witness showed a sensitivity of 76%, Snap of 81%, PetChek of 85% and HESKA antibody of 95% (Witness vs Snap p>0.05; Witness vs PetChek p>0.05; Witness vs HESKA p<0.05). Considering a heartworm prevalence of 6%, the positive predictive values are 100%, the predictive negative values were 98% for Witness and Snap and 99% for PetChek, respectively.