Screening under the microscope

Improvements to cervical tests, the expansion of cancer screening and the potential harm of any health screening will be examined at a two-day symposium.

Hosted by the Ministry of Health, the meeting in Wellington to debate the problems and opportunities of screening has attracted more than 50 speakers.

Organised health screening programmes in which patients are generally registered and recalled (and in which testing quality is regularly audited) can prevent sickness and save lives.

They are also expensive and can harm otherwise well people. This can happen when results are misread or a programme is poorly monitored - as revealed by the Gisborne cervical cancer inquiry - and when some patients are inevitably subjected to unnecessary treatment because of a false-positive test result.

The National Cervical Screening Programme, established in 1990, is credited by the ministry with reducing cervical cancer incidence by 39 per cent and mortality by 44 per cent.

BreastScreen Aotearoa, established in 1998 for women aged 50-64 and extended last year to those aged 45-69, costs taxpayers $40.5 million a year. Breast screening reduces the chances of dying from breast cancer by 20 per cent for women under 50 and from 30 to 45 per cent for women aged 50 to 69, the ministry says.

But in Gisborne, dozens of women developed cancer after the misreading of their cervical smears in the 1990s was not picked up. Some died.

"Screening is a basic element of any modern healthcare system. We have screening programmes that have really made a difference," Professor Alistair Woodward, the head of population health at Auckland University and the National Screening Advisory Committee's chairman, said yesterday.

Screening involved trading off big benefits for the few against small amounts of discomfort, economic costs and possibly health risks for the many.

"With screening for bowel cancer we have good evidence that picking up the disease early does permit more effective treatment. But what's holding us back from recommending a national screening programme is that trade-off issue."

That meant weighing people who would have unnecessary investigations and the associated costs against the enormous benefit for a relatively small number of people, he said.

The system

* New Zealand screens for cervical cancer, breast cancer and, in newborns, for metabolic disorders.

* Screening during pregnancy for HIV is being introduced.

* Universal screening programmes for bowel cancer, chlamydia and newborn hearing - but not prostate cancer - are being investigated.