title: Urdu version of the neck disability index: a reliability and validity study.
abstract: Despite the wide use of the neck disability index (NDI) for assessing disability in patients with neck pain, the NDI has not yet been translated and validated in Urdu. The first purpose of the present study was to translate and cross-culturally adapt the NDI into the Urdu language (NDI-U). The second purpose was to investigate the reliability, validity and responsiveness of the NDI-U in Urdu-speaking patients experiencing chronic mechanical neck pain (CMNP).
  
  
  
  Translation and cross-cultural adaptation of the original version of the NDI were carried out using previously described procedures. Seventy-six patients with CMNP and thirty healthy participants were recruited for the study. NDI-U and visual analogue scales for pain intensity (VASpain) and disability (VASdisability) were administered to all the participants at baseline and to the patients 3 weeks after receiving physiotherapy intervention. The global rating of change scale (GROC) was also administered at this time. Test-retest reliability and internal consistency were carried out on forty-six randomly selected patients two days after they completed the NDI-U. The NDI-U was evaluated for factor analysis, content validity, construct validity (discriminative and convergent validity) and responsiveness.
  
  
  
  An intra-class correlation coefficient (ICC2,1) revealed excellent test-retest reliability for all items (ICC2,1= 0.86-0.98) and total scores (ICC2,1= 0.99) of the NDI-U. The NDI-U was found internally consistent with a Cronbach's alpha of 0.90 and a fair to good correlation between single items and the NDI-U total scores (r = 0.34 to 0.89). Factor analysis of the NDI-U produced two factors explaining 66.71% of the variance. Content validity was good, as no floor or ceiling effects were detected for the NDI-U total score. To determine discriminative validity, an independent t-test revealed a significant difference in the NDI-U total scores between the patients and healthy controls (P < 0.001). For convergent validity, Pearson's correlation coefficient showed a strong correlation between NDI-U and VASdisability(r = 0.83, P < 0.001) and a moderate correlation between NDI-U and VASpain(r = 0.62, P < 0.001). To measure responsiveness, an independent t-test showed a significant difference in the NDI-U change scores between the stable and the improved groups (P < 0.001). Furthermore, moderate correlations were found between the NDI-U change scores and the GROC (r = 0.50, P < 0.001), VASdisabilitychange scores (r = 0.58, P < 0.001) and VASpainchange scores (r = 0.55, P < 0.001).
  
  
  
  The results showed that the NDI-U is a reliable, valid and responsive questionnaire to measure disability in Urdu-speaking patients with CMNP.
authors.affiliation: University Institute of Physical Therapy, Faculty of Allied Health Sciences, University of Lahore, Lahore, Pakistan.|Islamabad College of Physiotherapy, Margalla Institute of Health Sciences, Quaid-e-Azam Avenue, Gulrez III, Rawalpindi, Pakistan.
authors.forename: Muhammad Nazim
authors.initials: MN
authors.lastname: Farooq
authors.affiliation: University Institute of Physical Therapy, Faculty of Allied Health Sciences, University of Lahore, Lahore, Pakistan. mohseni_bandpei@yahoo.com.|Pediatric Neurorehabilitation Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. mohseni_bandpei@yahoo.com.
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Mohseni-Bandpei
authors.affiliation: Dean Faculty of Allied Health Sciences, Director; Directorate of International Linkages, University of Lahore, Lahore, Pakistan.
authors.forename: Syed Amir
authors.initials: SA
authors.lastname: Gilani
authors.affiliation: Physiotherapy Department, KRL General Hospital, Kahuta, Distt., Rawalpindi, Pakistan.
authors.forename: Ambreen
authors.initials: A
authors.lastname: Hafeez
mesh_terms: D000328:Adult; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019547:Neck Pain; D010154:Pakistan; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D055815:Young Adult
keywords: Disability; Neck; Reliability; Translations; Validity