ABSTRACT
BACKGROUND: Despite the existence of several screening tools for neuropathic pain, none of these are specific to surgery. We have developed a simple questionnaire tool, the Neuropathic Pain scale for Postsurgical patients (NeuPPS), to measure neuropathic pain in postsurgical patients. OBJECTIVES: The aim was to validate this tool in a breast cancer population using an item response theory model, resulting in an easy-to-use scale. STUDY DESIGN: Development was based on literature reviews and interviews with patients and experts and consisted of 6 items. It was tested among 2,217 long-term breast cancer survivors, and cross-validated in another data set of breast cancer survivors with 18 months follow-up. SETTING: We tested the questionnaire tool among breast cancer survivors in 2 cohorts, one nationwide and one of consecutively treated patients at Rigshospitalet, Copenhagen, Denmark. METHODS: Items were assessed for criterion-related construct validity using the Rasch model, and for convergent validity by comparison to another neuropathic pain screening tool, the self-report version of the Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) pain scale. RESULTS: The selected 5-item model showed good fit, unidimensionality, monotonicity, and homogeneity. This result was reproducible in the cross-validation population. In a combined dataset with data from both studies, the model displayed a slightly lower fit, suggesting that items to some degree may vary over time. The Spearman rank correlation between the NeuPPS and S-LANSS was P = 0.57. LIMITATIONS: We observed differential item functioning between the primary study population and the cross-validation population, meaning that some items behave differently at different follow-up times or study populations. CONCLUSIONS: With the NeuPPS, we have validated a simple and easy-to-fill-out questionnaire tool for the measurement of neuropathic pain among postsurgical patients. The items are additive, giving a total score that measures neuropathic pain symptoms. KEY WORDS: Scale validation, Rasch analysis, item response model, persistent postoperative pain, intercostobrachial nerve, neuropathy, neuropathic pain, quantitative sensory testing, breast cancer.
