Responsiveness and minimal important change of neck disability index and numeric pain rating scale for neck patients in the Norwegian neck and back register.

PURPOSE: To evaluate the responsiveness and the minimal important change (MIC) of Neck Disability Index (NDI) and pain during activity by the numeric rating scale (NRSa) in the Norwegian neck and back registry (NNRR).

MATERIALS AND

METHODS

Participants with neck pain responding to baseline, 6 and 12-months follow-up in the NNRR were included. Responsiveness was calculated using the area under the receiver operating characteristic (ROC). The minimal important change (MIC) was calculated with an anchor-based method and distribution-based methods. For the anchor-based method we used the Patient Global Impression of Change (PGIC) as the anchor. The PGIC was on a 7-point Likert scale, and trichotomized into three ordinal categories.

RESULTS

A total of 551 patients with neck pain were included. Among these patients, 60% were women with an average age of 48, and 63% had experienced neck pain for more than one year. For improved patients NDI and NRSa had adequate responsiveness at both follow-ups. MIC calculations using an anchor-based method were more accurate than those using a distribution-based method, which fell below the measurement error for the instruments. Using anchor-based calculation of MIC, the MIC for NDI was 17 at the 6-months follow-up and 9 at 12-months follow-up. Correspondingly, NRSa had a MIC of 2.5 at both follow-ups.

CONCLUSION

NDI and NRSa were responsive at both 6-months and 12-months follow-up and can be used in registries following patients with neck pain over time.