Short- and long-term test-retest reliability of the English version of the 7-item DN4 questionnaire - a screening tool for neuropathic pain.

Objectives: The original French version of the "Douleur Neuropathique en 4 Questions (DN4) questionnaire" is a valid screening tool for the identification of neuropathic pain (NeP). The DN4 has been translated into English, but the reliability of the English version has not yet been investigated. The aim of this study was to investigate the 7-item DN4 questionnaire in regards to short-term reliability before (T0) and immediately after (T1) the clinical examination and long-term reliability one week later (T2).

Methods: A total of 222 participants (age 56.33 ± 16 years, 56 % female) were recruited from a Pain Management Department and Neurosurgery Spinal Clinic. For T2 measurements, the 7-item DN4 was sent by post with the "Patient Global Impression of Change Scale". The scale detects possible changes of symptoms, scoring from "very much improved" (1) to "very much worse" (7). Only participants whose symptoms had not changed much (scores 3-5) were included in the T0-T2 analysis. Weighted Kappa was used to analyse the reliability of the DN4 total scores and unweighted Kappa for the DN4 classifications.

Results: Considering missing data and exclusions, data of 215 participants could be used for the T0-T1 and data of 103 participants for T0-T2 analysis. There was almost perfect agreement for the 7-item DN4 total score between T0-T1 (weighted k: 0.891, CI: 0.758-1.024) and T0-T2 (weighted k: 0.850, CI: 0.657-1.043). Classifications between neuropathic pain and no neuropathic pain showed almost perfect agreement (k: 0.835, CI: 0.755-0.915) for T0-T1 and substantial agreement (k: 0.733, CI: 0.598-0.868) for T0-T2.

Conclusions: The English 7-item DN4 is a reliable screening tool for neuropathic pain.

Ethical committee number: #RGS0000001759.