Psychometric properties of neck disability index - a systematic review and meta-analysis.

Abstract

To evaluate the data on the psychometric properties of the Neck Disability Index (NDI). Medline, Embase, PsychINFO, Web of Science, and Scopus were searched in April 2023. The random effects meta-analysis was conducted when possible. Of 492 identified records, 79 were included. 70 studies were considered to be of low risk of systematic bias. Alpha was >0.81. Pooled test-retest intraclass correlation coefficient was 0.91 (95% CI 0.90-0.93). The NDI correlations with pain rating scales varied from 0.38 to 0.89. 13 studies found the NDI to be unidimensional and 15 - two- or three-dimensional. The minimal detectable change varied from 3% to 27% and minimal clinically important difference from 5% to 33%. Pooled area under the curve was 0.74 (95% CI 0.68-0.80). Most studies have not detected floor or ceiling effect. Sex-related differential item functioning has been present in one study. The NDI demonstrated good internal consistency and test-retest reliability without floor or ceiling effect. In most situations, the NDI could be considered a unidimensional scale. The NDI well correlated with the common scales of pain and disability. The minimal clinically important difference and minimal detectable change were around 15% (7.5/50 points).