Comparison of 4 agar gel immunodiffusion kits for serologic detection of equine infectious anemia virus antibodies

Abstract

Using 85 sera collected from horses that had been experimentally infected with equine infectious anemia virus (EIAV) and 200 field sera collected from racehorses in Japan, we compared 4 agar gel immunodiffusion (AGID) kits for serologic detection of EIAV antibodies from Idexx, VMRD, IDvet, and the National Engineering Research Center of Veterinary Biologics, China (NECVB). The positive control lines were sufficiently clear in all kits for evaluation to be made, with slight differences in sharpness: NECVB was the sharpest, followed by VMRD, IDvet, and Idexx. The test results for all 285 samples agreed among the 4 kits, with 62 positives and 223 negatives. The sensitivities and specificities of VMRD, IDvet, and NECVB compared with the Idexx kit were 100%, and the kappa coefficient values between the kits were 1.0 for all combinations. We concluded that the testing capacity of these 4 kits was virtually identical.

Keywords: agar gel immunodiffusion test; equine infectious anemia; horses.

Figure 1.

Results of testing for equine infectious anemia viral antibody with agar gel immunodiffusion kits from Idexx, VMRD, IDvet, and the National Engineering Research Center of Veterinary Biologics, China (NECVB). A. Positive control lines formed between the antigen well (center) and positive control wells (left and right). B. Strong-positive lines formed between the antigen well (center) and the sample wells (top left and right, and bottom left and right). The serum in the upper left well was evaluated as being weakly positive with the NECVB kit, but strongly positive with the other kits. Similar differences in levels of positive reactions were observed for some of the other sera, but no samples were judged positive with one kit and negative with another. C. Weak-positive reactions between the antigen well (center) and the sample well (bottom left). The control line curved slightly toward the antigen well and away from the reference positive control serum well, but did not form a complete line between antigen and test serum.