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Doctors put diagnostic tools to good use

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General practitioners are ordering almost double the diagnostic imaging tests they were a decade ago as the number of patients and medical problems they treat has increased.

A University of Sydney study has prompted claims of over-servicing after it identified a 45 per cent increase in the number of x-rays and other tests ordered by GPs between 2002 and 2012, from around 8.45 million a year to 12.2 million.

In all the study, based on responses from 9802 GPs, found the rate of tests ordered during the period rose significantly, from 8.7 per 100 patient encounters to 10.2.

But the researchers, from the University’s Family Medicine Research Centre, found that in most circumstances the diagnostic imaging tests ordered by doctors were in accordance with clinical guidelines, and other factors were at play in driving growth.

Part of the explanation came from increased reliance of patients on GPs. There was almost a 25 per cent jump in the number of GP visits between 2002 and 2012, from 97 million to 120 million a year.

At the same time, the number of problems patients were presenting to their GP at each visit also increased significantly. The number of problems managed by family doctors rose from 149 per 100 patient encounters to almost 158. The researchers found that for each additional problem, the chance of a diagnostic imaging test being ordered increased 41 per cent.

Changes in technology and medical knowledge also played a role.  

The likelihood that a GP would order an imaging test to help manage a medical problem climbed from 5.3 to 5.8 per cent over the period.

But, although doctors were largely medically justified in the diagnostic imaging tests they ordered, there were some exceptions.

The study’s lead author, Dr Helena Britt, said GPs were found to be overly quick in ordering imaging tests for patients with back problems. They accounted for more than half of all imaging tests ordered.

For every 100 patients presenting with back problems, 17 were sent off for diagnostic imaging – most commonly x-rays (54 per cent), followed by CT scans (36 per cent) and MRIs (5 per cent).

The authors said the rate at which doctors referred patients presenting with back problems for the first time for imaging was “inconsistent with all established guidelines”.

“Expert guidelines advise caution in ordering tests for presenting back problems unless there is a red flag to prompt investigation,” Dr Britt said. “Red flags can include issues such as major trauma, unexplained weight loss, unexplained fever, a history of malignancy, inflammatory conditions and neurological issues.”

The study’s authors also found room for improvement in the use of imaging for patients with knee and ankle sprains and strains.

They found that reliance on x-rays for patients with knee problems could be “significantly reduced” by applying the Ottawa knee rules protocols, while doctors frequently ordered ultrasounds for ankle sprains and strains despite clinical guidelines to the contrary.

Despite these problems, the study concluded that doctors by large made appropriate use of diagnostic imaging tests.

“In general…Australian GPs select appropriate diagnostic imaging modalities for specific clinical problems, given the restraint imposed by restriction of MBS rebates for MRIs ordered by GPs,” the study found.

“Imaging ordering behaviour suggests broad compliance with published guidelines.”

Adrian Rollins