AIHW media releases

GPs order diagnostic imaging tests such as X-rays and CT scans at the rate of at least one test in every 13 consultations, according to a report released today by the Australian Institute of Health and Welfare.

Imaging Orders by General Practitioners in Australia 1999-00 suggests that if this rate is extrapolated to the total number of GP-patient consultations in Australia, then approximately 8 million diagnostic imaging tests were ordered by GPs in 1999-00.

Plain X-rays were the most common type of imaging ordered (63.7%), followed by ultrasound (25.7%), computerised tomography (CT scans) (8.5%), magnetic resonance imaging (MRIs)(0.3%) and nuclear medicine imaging (0.2%).

Director of the AIHW's General Practice and Statistics Classification Unit at the University of Sydney, Professor Helena Britt, says that GPs order about 60% of all imaging tests, with the remainder being ordered by specialists.

'8 million tests is a lot of tests, of course, but from our statistics, and reviews of the available guidelines, GP ordering behaviour follows the guidelines in most areas.'

'That's not to say there isn't room for improvement. For example, we think there is enough clinical evidence to suggest that a reduction in ordering of spinal, ankle and knee X-rays may be possible without affecting quality of care.

'We are also concerned about what we call "systemic blocks" on GP ordering of MRIs and MRAs (multiple resonance angiograms). Currently these tests are rebatable from Medicare only if ordered by a specialist. These blocks sometimes lead the GP to order a less suitable investigation.

'A more complex problem occurs with echocardiography-in summary, our data and overseas research suggest that the quality of care provided to general practice patients could be improved with increased use of echocardiography.

'Our other major concern is the apparent relationship of large practice size (11-15 GPs) with high rates of ordering, and overseas evidence of high ordering rates when there is co-ownership of imaging facilities and general practices. If corporatisation of general practice leads to increases in both the number of large practices and in co-ownership of imaging facilities and general practices, it is possible that imaging order rates will rise.'

Other findings in Imaging Orders by General Practitioners in Australia 1999-00 include:

• GPs in small rural areas are more likely to have high ordering rates, possibly a result of rural GPs doing their own X-rays, and/or conducting more detailed investigations before referral to a specialist (access to specialists is comparatively poor in country areas).
• The strongest independent predictor of high ordering rates is the rate of consultations with new patients.
• High rates of management of musculo-skeletal, urinary and female genital problems are also significant predictors of high ordering rates.