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Liquid-based cytology increases false positive rate

Using liquid-based cytology to screen for cervical cancer reduces the rate of unsatisfactory slides but has a lower predictive value than conventional cytology.

A new analysis, published online by the BMJ, found liquid-based cytology was no more sensitive than conventional cytology for detecting cervical intra- epithelial neoplasias of grade two or above.

But liquid-based cytology, which is set to be rolled out across the UK by next year, did detect more positive results, which lowered the positive predictive value to 42% below that of conventional cytology.

Some 2.6% of women whose samples were screened using liquid-based cytology had at least one unsatisfactory cytology result – significantly lower than the 4.1% screened using conventional cytology.

Study leader Dr Guglielmo Ronco, head of the cervical screening evaluation unit at the Centre for Cancer Prevention in Turin, concluded: 'On the basis of this analysis the main advantage of moving to liquid-based cytology is a reduction in the rate of unsatisfactory slides. More positive results were found, however, leading to a lower positive predictive value.'

Researchers studied 45,174 women aged 25 to 60 at nine screening centres in Italy.

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