00517649

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Clinical epidemiologic evaluation of BSE screening tests in Japan

English (英語)

The Kobe journal of the medical sciences

52(3/4)

49-59

Kobe University School of Medicine

2006-01

2007-02-27

To address the public concerns provoked by the first incidence of bovinespongiform encephalopathy (BSE) in Japan, the BSE screening tests in Japan areevaluated in use of modeling analysis in evidence-based diagnosis.Under the assumptions based on epidemiological statistics such as the annualnumber of screened cattle with 1,227,385, the annual incidence of BSE infection withfour, and the sensitivity of 99.0% for both primary and secondary tests, it wasestimated that, the current threshold of cut-off for the BSE positive would have 0.119false negatives per year. The decrease of the sensitivity of ELISA down to 90.0 %resulted in the increase up to 0.792 false negatives per year. Even with the 90.0%sensitivity, shifting the cut-off point from the current level to the best one remarkablyreduced the false negatives per year down to 0.0004. Regarding false positives, with99.7 % specificity for both ELISA and the confirmatory tests revealed the risk of 0.03false positives per year, while the cut-off shifting that can best minimize false negativeslargely increased the false positives up to 11,013.Although it is confirmed the possibility of false negatives is very low, the currentmethod of screening can be further improved by shifting the decision level of cut-off todefine the BSE 'positive'. Such an improvement, however, raises an issue oftrade-off : the less false negatives, the more false positives. We believe our approachcan help the public perception of an optimum decision-making for BSE screening,considering the trade-off.

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