In case of a positive screening test, confirmation of results must be carried out via more complex chemical analysis.

如果筛选检测呈阳性，就必须通过更加复杂的化学分析来确认结果。

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In addition, the early detection of breast cancers by the national breast screening programme has undoubtedly had a positive impact.

BBC: Breast cancer deaths plummet

It could be that screening is detecting more oestrogen-receptor positive cancers because they are slow-growing and may be detected before symptoms appear.

BBC: Breast cancer biology 'changing'

The Kerry campaign has been screening speeches all week to try to keep a positive emphasis.

CNN: Sharpton to Bush: Black vote 'is not for sale'