The Neck Disability Index (NDI) and, to a lesser extent, the Numeric Pain Rating Scale (NPRS) may represent reliable measures for patients to self-report cervicogenic headache-associated disability and pain in the short term, respectively, according to a study published in Cephalalgia.
Investigators conducted a secondary analysis of a randomized clinical trial in which 110 patients (average age, 35.2) with cervicogenic headache were treated with spinal manipulative therapy alone or in combination with exercise.
The NDI and NPRS were administered at 1 week, 4 weeks, and 3 months, and the reliability (assessed with the intraclass correlation coefficient [ICC]), construct validity, responsiveness, and thresholds for minimal detectable change and clinically important difference values for these 2 questionnaires were evaluated.
At 4 weeks, the NDI showed excellent reliability (ICC, 0.92), and the 0 to 10 NPRS showed moderate reliability (ICC, 0.72). At the 3-month follow-up, the NDI still demonstrated excellent reliability (ICC, 0.95), and the NPRS demonstrated poor and fair reliability (ICC, 0.48).
Regardless of time to follow-up and improvement category, both measures exhibited adequate responsiveness (area under curve range, 0.78-0.93) and construct validity (P <.001). The minimal detectable change at the 4-week follow-up for the NDI was 5.9 points compared with 2.4 points for the NPRS (both P <.001). On the basis of these findings, the researchers concluded that the interpretation of headache intensity values in the long term should be approached cautiously.
Among the study limitations, researchers noted common inconsistencies in the way parameters such as headache intensity, frequency, and medication intake are defined and measured.
“The NDI and NPRS seem well suited as short-term self-report outcome measures for patients with [cervicogenic headache],” concluded the study authors.
“Clinicians and researchers should expect at least a 2.5-point reduction on the numeric pain rating scale and a 5.5-point reduction on the neck disability index after 4 weeks of intervention to be considered clinically meaningful,” they added.
Young I, Dunning J, Butts R, Cleland J, Fernaández-de-las-Peñas C. Psychometric properties of the Numeric Pain Rating Scale and Neck Disability Index in patients with cervicogenic headache [published online April 19, 2018]. Cephalalgia. doi: 10.1177/0333102418772584