A study results reported that it may be possible to differentiate radicular from axial low back pain (LBP) using a new pain assessment tool. The study involved 130 patients with peripheral neuropathic pain caused by diabetic polyneuropathy, postherpetic neuralgia, or radicular LBP, and 57 patients with nonneuropathic (axial) LBP. Symptoms and signs were prospectively evaluated with a structured interview (16 questions) and a standardized bedside examination (23 tests). Using hierarchical cluster analysis, the investigators identified distinct association patterns of symptoms and signs that characterized 6 subtypes of patients with neuropathic pain and 2 with nonneuropathic pain. The 6 interview questions and 10 physical tests that best discriminated these pain subtypes were determined with a classification tree analysis. These assessment items were combined in a pain assessment tool that the investigators named Standardized Evaluation of Pain (StEP). In an independent group of 137 patients, StEP was validated for the ability to distinguish radicular LBP from axial LBP. For the identification of radicular pain, the sensitivity of StEP was 92% (95% confidence interval [CI], 83% - 97%) and specificity was 97% (95% CI, 89% - 100%). The diagnostic accuracy of StEP was superior to that of a dedicated screening tool for neuropathic pain and spinal magnetic resonance imaging. The investigators were also able to reproduce subtypes of radicular and axial LBP, confirming that StEP is useful for distinguishing specific patterns of symptoms and signs.