Responsiveness of the Neck Disability Index in patients with mechanical neck disorders.
OBJECTIVE
Report the test-retest reliability, construct validity, minimum clinically important difference (MCID), and minimal detectable change (MDC) for the Neck Disability Index (NDI).


METHODS
Cohort study of patients presenting to outpatient physical therapy clinics.


METHODS
Ninety-one subjects with a primary complaint of neck pain, with or without concomitant upper extremity (UE) symptoms, who were participants in a randomized clinical trial.


METHODS
NDI and the 15-point Global Rating of Change (GRC) self-report measures.


METHODS
All subjects completed the NDI at baseline and at a 3-week follow-up. Additionally, subjects completed the GRC scale, which was used to dichotomize patients into improved or stable groups. Changes in the NDI were used to assess test-retest reliability, construct validity, MCID, and MDC.


RESULTS
Test-retest reliability was moderate for the NDI (intraclass correlation coefficient, 0.64; 95% confidence interval, 0.19-0.84). For the NDI, the MCID was 7.5 points and the MDC was 10.2 points.


CONCLUSIONS
The NDI appears to demonstrate adequate responsiveness based on statistical reference criteria when used in a sample that approximates the high percentage of patients with neck pain and concomitant UE referred symptoms. Because the MCID is within the bounds of measurement error, a 10-point change (the MDC) should be used as the MCID.
Young
Brian A
BA
Department of Physical Therapy, Sheppard AFB, TX, USA. byoungpt@earthlink.net
Walker
Michael J
MJ
Strunce
Joseph B
JB
Boyles
Robert E
RE
Whitman
Julie M
JM
Childs
John D
JD
D019540:Area Under Curve; D015331:Cohort Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D019547:Neck Pain / Q000534:rehabilitation*; D012372:ROC Curve; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012720:Severity of Illness Index