Reliability and validity of the finnish version of the neck disability index and the modified neck pain and disability scale.
METHODS
Translation and psychometric testing.


OBJECTIVE
To cross-culturally adapt the Neck Disability Index (NDI) to the Finnish language and to assess the reliability and validity of the Finnish version of the Neck Disability Index (NDI-FI) and the modified Neck Pain and Disability Scale (mNPDS-FI) in Finnish patients with neck pain.


BACKGROUND
Although largely used, no previous reports exist on the translation process or the testing of the psychometric properties of the Finnish version of the NDI or the mNPDS used in Finland.


METHODS
The translation of the questionnaire from English into Finnish was done in accordance with the published guidelines. A total of 101 patients with neck pain participated in the study. The reliability of the questionnaires was tested using a test-retest procedure at 2-week intervals. Further psychometric testing was done by assessing the construct validity and internal consistency of the questionnaires.


RESULTS
Test-retest reliability (intraclass correlation coefficients) was excellent for the NDI-FI (0.94) and mNPDS-FI (0.91). Factor analysis identified 1 factor for the NDI-FI and 3 factors for the mNPDS-FI; pain intensity, work ability, and activities of daily living. The internal consistency value (Cronbach alpha) for the NDI-FI was 0.85, and 0.84, 0.83, and 0.82, respectively, for the 3 factors of the mNPDS-FI. The correlation between neck pain and the NDI-FI was 0.58 (P < 0.001) and 0.72 for the mNPDS-FI (P < 0.001). A statistically significant linear relationship was observed between self-estimated coping and the outcomes of the NDI-FI and the mNPDS-FI.


CONCLUSIONS
The NDI-FI and the mNPDS-FI are reliable, valid instruments for assessing disability among Finnish patients with neck pain.
Department of Physical and Rehabilitation Medicine, Central Finland Health Care District, Jyväskylä, Finland. petri.k.salo@jyu.fi
Petri
P
Salo
Jari
J
Ylinen
Hannu
H
Kautiainen
Marja
M
Arkela-Kautiainen
Arja
A
Häkkinen
D000203:Activities of Daily Living; D000223:Adaptation, Psychological; D000328:Adult; D000368:Aged; D003431:Cross-Cultural Comparison; D004185:Disability Evaluation; D005260:Female; D005387:Finland; D006801:Humans; D008297:Male; D008875:Middle Aged; D019547:Neck Pain / Q000175:diagnosis*; D010147:Pain Measurement / Q000592:standards*; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards