Assessing neuropathic pain in patients with low back-related leg pain: Comparing the painDETECT Questionnaire with the 2016 NeuPSIG grading system.

BACKGROUND: Low back-related leg pain with nerve root involvement is conceptually regarded as a neuropathic condition. However, it is uncertain to what extent patients with this condition can be formally classified with neuropathic pain.

METHOD: First, we used the 2016 revision of the IASP Special Interest Group on Neuropathic Pain (NeuPSIG) grading system for neuropathic pain to grade patients suffering from low back-related leg pain and a corresponding disc herniation with either unlikely, possible, probable or definite neuropathic pain. Examination included bedside quantitative sensory testing. Next, we used the clinical classification based on the 2016 NeuPSIG grading system as a reference standard to assess the ability of the painDETECT Questionnaire to identify patients with neuropathic pain.

RESULTS: Of the 50 included patients, six (12%) fulfilled the clinical classification criteria for probable and 44 (88%) for definite neuropathic pain, while none were graded unlikely or possible. According to painDETECT, 23 patients (46%) were classified with unlikely neuropathic pain, 18 patients (36%) had an uncertain condition and in nine patients (18%) neuropathic pain was likely. Among the 44 patients graded as having definite neuropathic pain by the clinical classification, eight were classified as likely neuropathic pain by painDETECT, resulting in an agreement of 18%. Of these 44 patients graded with definite neuropathic pain, painDETECT classified 21 patients (48%) as unlikely and 15 (34%) as uncertain.

CONCLUSION: Our results do not support the use of painDETECT as a screening tool to classify or grade neuropathic components in patients with low back-related leg pain.

SIGNIFICANCE: The painDETECT Questionnaire performed poorly at detecting neuropathic pain among patients with low back-related leg pain, compared to clinical examination based on the 2016 NeuPSIG grading system as a reference standard. Our results do not support the use of painDETECT as a screening tool to classify or grade neuropathic components in this population.