Croatian version of the neck disability index can distinguish between acute, chronic and no neck pain: Results of a validation study

Summary Objective Longitudinal study to test the validity and reliability of the Croatian version of the neck disability index (NDI-CRO) for use in patients. Methods Three groups were given NDI-CRO on two occasions, 48 h apart: acute whiplash neck injury group ( n = 30), hospital physiotherapists—professional chronic neck pain group ( n = 56) and control group ( n = 65). To test validity, correlation between NDI-CRO and the pain VAS and PHQ‑9 questionnaire for depression was analyzed. Reliability testing was done using the test-retest experiment and item-total score correlation. Results Test-retest showed excellent correlation in all groups: whiplash 0.86, control 0.95 and physiotherapist 0.89 (Spearman r). Item-total score in the 3 analyzed groups showed positive correlation in all 10 categories, varying from 0.43–0.85. The NDI-CRO score showed significant difference between groups (median whiplash 38%, physiotherapist 12% and control 6%, p