Reliability and validity of the Mizo-version of neck disability index for non-specific neck pain in the rural North-East Indian population

ABSTRACT

Background: The Neck Disability Index (NDI) is an important self-assessment tool used extensively worldwide, in clinical practice with implications into scientific research fields. It is used to assess the extent of pain and levels of functional disability associated with neck pain. The NDI consists of 10 items where each item was scored from a scale of 0 to 5 giving the maximum score possible to 50. Though proven to be a reliable instrument in the English-speaking population, the NDI has never been validated and culturally adapted in the Mizo language among the rural north-east Indian region where English is not spoken as means of communication. The aim is to translate and cross culturally adapt the NDI into Mizo tawng (official language of Mizoram) with the objective of establishing reliability and validity of the M-NDI in patients with non-specific neck pain.Methods: A total of 49 subjects participated voluntarily from the rural primary health care, Lunglei district, Mizoram. Subject having chronic non-specific neck pain lasting more than 3 months were included after taking a written formal consent.Results: The internal consistency determined by Cronbach alpha, and the Intraclass Correlation Coefficient (ICC) using the test-retest reliability showed a good and an excellent reliability respectively (α=0.82, ICC=0.97, 95% CI= 0.95-0.98). Construct validity was determined between the variables-Numerical Pain Rating Scale (NPRS) and NDI by Pearson’s correlation coefficient and found to have a good correlation r=0.89 and significant difference at p<0.001.Conclusions: The study results concluded the Mizo version of NDI to be easy to understand, reliable and valid instrument for measuring disability and functional limitations of daily activities in non-specific neck pain in the Mizo speaking population.