Less is More: Five-item Neck Disability Index to Assess Chronic Neck Pain Patients in Brazil.

Study Design: Cross-sectional study.

Objective: The aim of this study was to assess the structural validity of the Brazilian version of the Neck Disability Index (NDI) in patients with chronic neck pain.

Summary Of Background Data: NDI is widely used in clinical and scientific contexts, although its structure has not been evaluated in the Brazilian version.

Methods: Native Brazilian Portuguese speakers, aged ≥18 years, with neck pain complaint of at least 3 months, and minimal pain rating of 3 points at rest or during neck movements were included. Exploratory factorial analysis (EFA) and confirmatory factorial analysis (CFA) were used. In EFA, the adequacy of the model was assessed using Bartlett test of sphericity and Kaiser-Meyer-Olkin test. In CFA, the goodness-of-fit was assessed by the indices: root mean square error of approximation with 90% of confidence interval, comparative fit index, Tucker-Lewis Index, standardized root mean square residual, and χ2/degree of freedom. Akaike information criterion (AIC) and Bayesian information criterion (BIC) were considered to compare the models.

Results: Two hundred fifty-four participants with chronic neck pain were included. The NDI model with one domain and five items presented the most adequate goodness-of-fit indexes and the lowest values of AIC and BIC, when compared with models with one domain and 10, eight, or seven items, and with the model with two domains and 10 items.

Conclusion: In the Brazilian context, the NDI version with one domain and five items (personal care, concentration, work, driving, and recreation) presents the best structure according to the factorial analysis.Level of Evidence: 5.