Validation of DN4 as a screening tool for neuropathic pain in painful diabetic polyneuropathy

Aims:  DN4 (Douleur Neuropathique en 4 Questions) is a screening tool for neuropathic pain consisting of interview questions (DN4-interview) and physical tests. It has not formally been validated in diabetes. We evaluated the validity and diagnostic accuracy of DN4 and DN4-interview in identifying neuropathic pain of painful diabetic polyneuropathy. Methods: In 158 patients with diabetes, the presence of diabetic polyneuropathy and neuropathic pain was assessed using scoring system for symptoms and signs, quantitative sensory testing, nerve conduction studies, pain history, numerical rating scale, and Short-Form McGill Pain Questionnaire. Painful diabetic polyneuropathy was defined as the presence of diabetic polyneuropathy plus chronic neuropathic pain in the same area as neuropathic deficits. A blinded investigator performed DN4. Results:  The DN4 score was significantly related to all the neurological and electrophysiological measurements and to Short-Form McGill Pain Questionnaire (ρ = 0.58, P < 0.0001). DN4 and DN4-interview scores showed a high diagnostic accuracy for painful diabetic peripheral neuropathy with areas under the receiver operating characteristic curve of 0.94 and 0.93, respectively. At the cut-off of 4, DN4 displayed sensitivity of 80%, specificity of 92%, positive predictive value (PPV) of 82%, negative predictive value (NPV) of 91%, and likelihood ratio for a positive result (LR(+) ) of 9.6. At the cut-off of 3, DN4-interview showed sensitivity and specificity of 84%, PPV of 71%, NPV of 92%, and LR(+) of 5.3. Conclusions:  This is the first validation study of DN4 for painful diabetic peripheral neuropathy, which supports its usefulness as both a screening tool for neuropathic pain in diabetes and a reliable component of the diagnostic work up.