ArticlesImaging strategies for low-back pain: systematic review and meta-analysis
Introduction
Studies have consistently shown that clinicians vary widely in how frequently they obtain imaging tests for assessment of low-back pain.1, 2, 3 In the absence of historical or clinical features (so-called red flags), suggestive of a serious underlying condition (such as cancer, infection, or cauda equina syndrome), the 1994 Agency for Healthcare Policy and Research (AHCPR) guideline made recommendations against lumbar imaging in the first month of acute low-back pain.4 These recommendations were based on observational studies that indicated a low frequency of serious conditions in patients without red flags,5, 6 weak correlation between findings on lumbar imaging studies and clinical symptoms,7 high likelihood for acute low-back pain to improve,8 and lack of evidence that imaging is helpful for guiding treatment decisions.9 Clinical guidelines for acute low-back pain published after 1994 have consistently recommended a similar approach.10 Some guidelines have also advised against lumbar imaging for chronic low-back pain without red flags.
Some clinicians still do lumbar-spine imaging routinely or without a clear indication,3 possibly because they aim to reassure their patients and themselves, to meet patient expectations about diagnostic tests, to identify a specific anatomical diagnosis for low-back pain, or because reimbursement structures provide financial incentives to image.11, 12, 13 However, imaging can be harmful because of radiation exposure (radiography and CT) and risks of labelling of patients with an anatomic diagnosis that might not be the actual cause of symptoms.14, 15 Furthermore, imaging studies have high direct and indirect costs. Increased frequency of lumbar MRI is associated with higher rates of spine surgery, without clear differences in patient outcomes.16, 17
Most diagnostic imaging studies quantify test accuracy for the identification of the presence or absence of disease compared with an established reference standard. For low-back pain, such studies are difficult to interpret because no reference standard reliably differentiates symptomatic from asymptomatic spinal imaging abnormalities.14, 18 Furthermore, studies of diagnostic-test accuracy do not investigate effects on clinical decision making or patient outcomes. By contrast, randomised trials that assess clinical outcomes incorporate effects of test results on subsequent treatments and are regarded as the strongest evidence for the assessment of diagnostic tests.19
Since the publication of the AHCPR guidelines, several randomised trials of immediate, routine lumbar imaging versus usual clinical care without immediate imaging have been published.20, 21, 22, 23, 24 In some trials, small differences have been reported in favour of routine imaging, but results have not always been significant. In such situations, meta-analyses can be helpful to assess whether a true difference exists, by increasing statistical power.25 The purpose of this systematic review and meta-analysis was to see whether immediate, routine lumbar-spine imaging is more effective than usual clinical care without immediate lumbar imaging in patients with low-back pain and no features suggesting a serious underlying condition.
Section snippets
Procedures
We searched Medline (from 1966 to first week of August, 2008) and the Cochrane Central Register of Controlled Trials (third quarter of 2008), with the terms “spine”, “low-back pain”, “diagnostic imaging”, and “randomised controlled trials” (see webpanel for complete search strategy). We reviewed reference lists for additional citations.
We included randomised controlled trials that compared immediate, routine lumbar imaging (or routine provision of imaging findings) versus usual clinical care
Results
Figure 1 shows the flow chart of studies from initial results of publication searches to final inclusion or exclusion. Of the six trials that met inclusion criteria, four, reported in six publications, assessed lumbar radiography20, 22, 23, 28, 29, 30 and two, reported in four publications, assessed MRI or CT.21, 24, 26, 27 We excluded two randomised trials that compared rapid MRI with plain radiography16, 41 and one non-randomised study.9
1804 patients were randomly assigned in six trials.20, 21
Discussion
Our meta-analysis of randomised controlled trials showed that immediate, routine lumbar-spine imaging in patients with low-back pain and no features suggesting serious underlying conditions did not improve clinical outcomes compared with usual clinical care without immediate imaging. Results were limited by small numbers of trials for some analyses, but seemed consistent for the primary outcomes of pain and function, and for quality of life, mental health, and overall improvement. Data for
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