A 45 per cent rise in diagnostic imaging tests ordered by Australian GPs is being driven by increasing GP visits, a rising number of problems managed at consultations and a higher likelihood that GPs order imaging tests for these problems, according to a new University of Sydney study.
Based on a long term national survey of 9,802 GPs between 2002 and 2012, the report draws on data from more than 980,000 GP-patient encounter records to assess the extent to which GP's order tests in line with diagnostic imaging guidelines.
"Most imaging tests ordered by GPs comply with expert guidelines," says the report's lead author, Dr Helena Britt. "However, the study indicates that GPs are too quick to order imaging tests during their initial assessment of back problems. GPs are twice as likely to order an imaging test during the initial examination of new back-problems compared to follow-up consultations.
"Expert guidelines advise caution in ordering tests for presenting back problems unless there is a 'red flag' to prompt investigation," says Dr Britt. "'Red flags' can include issues such as major trauma, unexplained weight loss, unexplained fever, history of malignancy, inflammatory conditions and neurological issues. However, patients with 'red flags' account for a small proportion of people presenting with new back problems."
Overall, diagnostic radiology (plain x-rays) was the test type most frequently ordered by GPs (54 per cent), followed by computerised tomography (36 per cent), magnetic resonance imaging (5 per cent) and ultrasound (3 per cent). The study also notes a trend away from diagnostic radiology to CT and MRI orders, in line with changing recommendations in the guidelines.
The four strongest predictors of whether GPs order a diagnostic imaging test are:
Number of problems managed at the GP-visit - each additional problem managed increases the probability of testing by 41 per cent.
- Type of medical problem managed - particularly musculoskeletal problems, female genital issues, pregnancy and family planning issues.
- Patient characteristics - females, those aged 45 years and older, and new patients.
- GP characteristics - women, GPs aged 35-44 years, those in solo practice, and those in a practice co-located with an imaging service.