%0 Journal Article
%T A hematologic key for bovine leukemia virus screening in Japanese black cattle
%A Masataka Akagami
%A Satoko Seki
%A Shoko Oya
%A Yoko Hayama
%A Yoshinao Ouchi
%A Yuki Kashima
%J Journal of Veterinary Diagnostic Investigation
%@ 1943-4936
%D 2019
%R 10.1177/1040638719848449
%X The European Community¡¯s leukosis key (EC key) is a well-known hematologic method for detecting bovine leukemia virus (BLV) infection in dairy cattle. The key identifies infected cattle with persistent lymphocytosis via a combination of lymphocyte count (LC) and age. Using the EC key to identify BLV-infected Japanese black (JB) cattle is problematic, however, given the inherently lower LCs of JB cattle compared to dairy cattle. We analyzed the LC in BLV-positive and -negative JB cattle and estimated LC cutoff values by age using receiver operating characteristic curve analysis. Among the 716 JB blood samples collected, 452 (63%) JB cattle were confirmed as BLV-positive by an antibody ELISA for ¡Ý1-y-old cattle and by real-time PCR for <1-y-old cattle. The cutoff values for the LC in each age group were calculated as 6.3 ¡Á 109/L for <1£¿y, 5.9 ¡Á 109/L for 1 to <2£¿y, 5.5 ¡Á 109/L for 2 to <3 y, 4.5 ¡Á 109/L for 3 to <6£¿y, 4.3 ¡Á 109/L for 6 to ¡Ü10£¿y, and 3.7 ¡Á 109/L for >10£¿y. The sensitivity and specificity of the estimated cutoff values were 0.49 (95% confidence interval: 0.44¨C0.53) and 0.81 (0.75¨C0.85), whereas those of the EC key were 0.20 (0.16¨C0.24) and 0.99 (0.97¨C1.00). Our LC cutoff values for screening JB cattle for BLV infection appear to be preferable to those of the EC key
%K bovine leukemia virus
%K Japanese black cattle
%K lymphocyte count
%K lymphocytosis
%K ROC analysis
%U https://journals.sagepub.com/doi/full/10.1177/1040638719848449