Outcome Measure Review – The Neck Disability Index

Submitted by: Jake Tumber, PT 

What is the Neck Disability Index used for?

The Neck Disability Index (NDI) was developed in the late 1980’s and published in 1991 to measure self-rated pain and disability in patients with neck pain. It comprises 10 sections, each with a score up to 5, for a total of 50 (1). The original developers suggested the following breakdown of NDI scores (2):

0-4:  no disability

5-14: mild disability

15-24: moderate disability

25-34: severe disability

35 or over: complete disability

What population is the NDI appropriate for?

The NDI has demonstrated excellent validity and re-test reliability in both acute and chronic populations, as well as neck pain associated with whiplash-associated disorders (WAD) and cervical radiculopathy (1).

Prognostic capabilities and detecting change over time.

Minimal Detectable Change is considered to be 5 points, with some studies suggesting as many as 10 points for radiculopathy (eg WAD3). The Clinically Important Difference is approximately 7 points. The studies suggest a re-test timeframe of 2 weeks to allow change. There is a floor-ceiling effect with the NDI; for patients who score either 40-50 or 0-10, subsequent change will be difficult to detect. Recent research has suggested that an NDI score of greater than 14.5/50 was one variable suggesting a poor outcome following acute whiplash injury (3).

References

1. MacDermid, JC et al. Measurement Properties of the Neck Disability Index: A Systematic Review.  J Orthop Sports Phys Ther 2009;39(5):400-417
2. Vernon, HT, Mior, SA.  The Neck Disability Index: a study of reliability and validity. J Manip Physiol Ther 1991;14:409-415
3. Walton, DM et al. Risk Factors for Persistent Problems Following Acute Whiplash: Update of a Systematic Review and Meta-analysis. J Orthop Sports Phys Ther 2013;43(2):31-43.