Magnetic resonance imaging of the lumbar spine: determining clinical impact and potential harm from overuse.

BACKGROUND: Lumbar spine magnetic resonance imaging is frequently said to be "overused" in the evaluation of low back pain, yet data concerning the extent of overuse and the potential harmful effects are lacking.

PURPOSE: The objective of this study was to determine the proportion of examinations with a detectable impact on patient care (actionable outcomes).

STUDY DESIGN: This is a retrospective cohort study.

PATIENT SAMPLE: A total of 5,365 outpatient lumbar spine magnetic resonance (MR) examinations were conducted.

OUTCOME MEASURES: Actionable outcomes included (1) findings leading to an intervention making use of anatomical information such as surgery; (2) new diagnoses of cancer, infection, or fracture; or (3) following known lumbar spine pathology. Potential harm was assessed by identifying examinations where suspicion of cancer or infection was raised but no positive diagnosis made.

METHODS: A medical record aggregation/search system was used to identify lumbar spine MR examinations with positive outcome measures. Patient notes were examined to verify outcomes. A random sample was manually inspected to identify missed positive outcomes.

RESULTS: The proportion of actionable lumbar spine magnetic resonance imaging was 13%, although 93% were appropriate according to the American College of Radiology guidelines. Of 36 suspected cases of cancer or infection, 81% were false positives. Further investigations were ordered on 59% of suspicious examinations, 86% of which were false positives.

CONCLUSIONS: The proportion of lumbar spine MR examinations that inform management is small. The false-positive rate and the proportion of false positives involving further investigation are high. Further study to improve the efficiency of imaging is warranted.