Influence of magnetic resonance imaging of the knee on GPs' decisions: a randomised trial DAMASK:(Direct Access to Magnetic Resonance Imaging: Assessment for Suspect Knees) Trial Team

Background

Magnetic resonance imaging (MRI) of the knee for meniscus and ligament injuries is an accurate diagnostic test. Early and accurate diagnosis of patients with knee problems may prevent the onset of chronic problems such as osteoarthritis, a common cause of disability in older people consulting their GP.

Aim

To assess the effect of early access to MRI, compared with referral to an orthopaedic specialist, on GPs' diagnoses and treatment plans for patients with knee problems.

Design of Study

A multicentre, pragmatic, randomised controlled trial.

Setting

Five hundred and fifty-three patients with knee problems were recruited from 163 general practices across the UK from November 2002 to October 2004.

Method

Eligible patients were randomised to MRI or consultation with an orthopaedic specialist. GPs made a concomitant provisional referral to orthopaedics for patients who were allocated to imaging. GPs recorded patients' diagnoses, treatment plans, and their confidence in these decisions at trial entry and follow-up. Data were analysed as intention to treat.

Results

There was no significant difference between MRI and orthopaedic groups for changes in diagnosis (P = 0.79) or treatment plans (P = 0.059). Significant changes in diagnostic and therapeutic confidence were observed for both groups with a greater increase in diagnostic confidence (P<0.001) and therapeutic confidence (P = 0.002) in the MRI group. There was a significant increase in within-group changes in diagnostic and therapeutic confidence.

Conclusion

Access to MRI did not significantly alter GPs' diagnoses or treatment plans compared with direct referral to an orthopaedic specialist, but access to MRI significantly increased their confidence in these decisions.