Agar gel immunodiffusion test for the detection of bovine leukemia virus antibodies: lack of trans-Atlantic standardization

Two agar gel immunodiffusion (AGID) kits for the serodiagnosis of bovine le ukemia virus (BLV) were imported from Europe and were compared with North A merican kits. The BLV AGID kits from North America and from Europe differed significantly, The punches were different, as were the pattern distributio n in the agar of the reference and the test sera, resulting in differences in the reading of the immunoprecipitation lines. Based on the testing of 12 00 serum samples from cattle, the European kits gave a good correlation wit h the American kits, as indicated by their respective kappa values. However , the European kits were found to be less sensitive when evaluated against weakly positive samples from field specimens or following a dilution trial. Only 65% and 50% of the weakly positive samples detected by the American k it #1 were detected by the European kits #2 and #3, respectively. The Ameri can kit was also capable of detecting BLV antibodies in 45% of strongly pos itive samples diluted 1/50 in negative sera, while antibodies were detected in only 15% of the samples with the European kit #2 and in none of the sam ples with the European kit #3. False negatives were also detected with the European kits. Among the false negatives, the degree of expected reactions was weak (European kit #2) or of varying degrees of positivity (European ki t #3). Besides the differences in format and performance, the BLV-AGID kits in Europe are evaluated with the National Standard Serum E4 while a profic iency panel composed of a quadruplicate set of 10 reference sera is used in Canada to monitor the kits. Based on the overall observations, we noted a lack of standardization between the BLV-AGID kits used in North America and in Europe.