Psychometric properties of the Numeric Pain Rating Scale and Neck Disability Index in patients with cervicogenic headache

Background Self-reported disability and pain intensity are commonly used outcomes in patients with cervicogenic headaches. However, there is a paucity of psychometric evidence to support the use of these self-report outcomes for individuals treated with cervicogenic headaches. Therefore, it is unknown if these measures are reliable, responsive, or result in meaningful clinically important changes in this patient population. Methods A secondary analysis of a randomized clinical trial (n = 110) examining the effects of spinal manipulative therapy with and without exercise in patients with cervicogenic headaches. Reliability, construct validity, responsiveness and thresholds for minimal detectable change and clinically important difference values were calculated for the Neck Disability Index and Numeric Pain Rating Scale. Results The Neck Disability Index exhibited excellent reliability (ICC = 0.92; [95 % CI: 0.46-0.97]), while the Numeric Pain Rating Scale exhibited moderate reliability (ICC = 0.72; [95 % CI: 0.08-0.90]) in the short term. Both instruments also exhibited adequate responsiveness (area under the curve; range = 0.78-0.93) and construct validity (p < 0.001) in this headache population. Conclusions Both instruments seem well suited as short-term self-report measures for patients with cervicogenic headaches. 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.