Sensitivity to Change

To the Editor: A recent issue of Physical Therapy contained a 2-part series investigating the Roland-Morris Back Pain Disability Scale (RMQ).1,2 In these articles, the authors provided further evidence regarding the ability of the RMQ to detect meaningful change over time in patients with low back pain. I would like to comment on the authors' use of the term “sensitivity to change” to describe this measure. Sensitivity to change is defined in the first article as “the capacity of a measure to detect change in patients' functional status over time”1(p1188) and in the second article as dealing with “the clinical meaningfulness of changes in scores.”2(p1198) The term typically applied to this measurement property is “responsiveness,” not “sensitivity to change.” “Responsiveness” is, indeed, the term used by Kirshner and Guyatt,3 whom the authors of the first article1 reference when describing the measure properly. Although the terms “responsiveness” and “sensitivity to change” are interrelated, they convey a somewhat different meaning, and the proper term to describe the measure investigated in the studies by Riddle et al2 and Stratford et al1 is “responsiveness,” not “sensitivity to change.”