Clinical epidemiologic evaluation of BSE screening tests in Japan
Yanagisawa, S.; Kamae, I.
Kobe Journal of Medical Sciences 52(3-4): 49-59
2006
ISSN/ISBN: 0023-2513 PMID: 16849872 Document Number: 600525
To address public concerns provoked by the first incidence of bovine spongiform encephalopathy (BSE) in Japan, the BSE screening tests in Japan were evaluated. Under hypothetical conditions (i.e., annual number of screened cattle in Japan, 1 227 385; annual BSE incidence, 4 cases per year; and sensitivity of 99.0% for both the ELISA and the confirmatory test), the rate of false negative BSE would be 0.119 per year. Decreasing the sensitivity of ELISA to 90.0% resulted in an increase of up to 0.792 false negative BSE per year. Even with the 90.0% sensitivity, shifting the cut-off point from the current level to the best one remarkably reduced the false negatives per year to 0.0004. Having a 99.7% specificity for both ELISA and the confirmatory test resulted to 0.03 false positive BSE per year. Although the possibility of false negatives is very low, the current method of screening can be further improved by shifting the cut-off value. Such an improvement, however, raises an issue of trade-off: the less false negatives, the more false positives.