Predictive Validity of Lumbar X-ray Images and MRIs for Chronic Low Back Pain Subtypes

Abstract

Purpose: The aim of this observational study alongside our inter-rater reliability trial (ISRCTN 43417727) is to investigate the accuracy of lumbar X-ray images and MRIs as diagnostic tools of low back pain (LBP) subtypes (sacroiliac joint, disc and facet joint).Patients and methods: Included were patients aged 18 or more with medical history and physical examination suggestive of a chronic LBP subtype, followed by a diagnostic test block. Numbers of spinal imaging tests, and whether or not pathology was present was evaluated in patients with positive- as well as negative diagnostic test blocks. The sensitivity, specificity, positive and negative predictive value of the lumbar X-ray images and MRIs discriminating between the three LBP subtypes are presented.Results: One hundred patients were included. Facet joint pain was a general working diagnosis in 40 patients, disc pain in 8 patients and SI joint pain in 35 patients. The positive predictive value of X-ray was 82.6% for facet joint pain, 66.7% for disc pain and 60% for SI joint pain; the negative predictive value of X-ray was 50% for facet joint pain, 66.7% for disc pain and 7.7% for SI joint pain. The positive predictive value of MRI was 81.8% for facet joint pain, 50% for disc pain and 0% for SI joint pain; the negative predictive value of MRI was 55.6% for facet joint pain, 0% for disc pain and 13% for SI joint pain.Conclusion: The predictive validity of lumbar X-ray images and MRIs to distinguish between low back pain subtypes in patients with chronic LBP is questionable.