Can guidelines impact the ordering of magnetic resonance imaging studies by primary care providers for low back pain?

OBJECTIVE: To compare primary care providers' (PCPs') use of lumbar spine magnetic resonance imaging (MRI) studies and surgical referrals for patients with low back pain (LBP) before and after dissemination of the 1994 Agency for Healthcare Policy and Research (AHCPR) LBP guidelines.
DESIGN: Retrospective cohort study. PATIENTS AND METHODS: Computerized audits identified patients with LBP evaluated by PCPs in 1994 or 1996 at a university-affiliated Veterans Affairs medical center who had an MRI order and/or a surgical referral. Research assistants recorded patients' demographic characteristics, LBP-related symptoms, and whether the PCP ordered an MRI and/or a surgery consult. For patients referred to surgery without an MRI, subsequent MRI orders by surgeons were recorded. We compared patient characteristics and utilization patterns for 1994 and 1996 and identified independent predictors of MRI orders.
RESULTS: PCPs saw 279 and 261 patients with LBP in 1994 and 1996, respectively. An almost identical number of MRIs were ordered in 1994 (99 by PCPs and 42 by surgeons) and 1996 (105 by PCPs and 32 by surgeons). Nearly 50% of patients meeting AHCPR guidelines underwent an MRI in 1994 or 1996. PCPs more frequently ordered a surgery consult in 1994 than in 1996. Providers were less likely to order an MRI for patients with a previous MRI and more likely to order an MRI for those seen in an urgent visit clinic. Neither year nor meeting AHCPR guidelines predicted MRI ordering.
CONCLUSIONS: Orders for MRI did not decrease after education on the guidelines. Limiting MRI orders to only "appropriate" patients would not have changed the observed results.