Test-retest repeatability of the McGill pain map (MPM) in persons with post-operative pain

Objective: Mapping pain location by self-report my be useful in determining the effect of pain location on functional status. However, the reliability of reporting pain location is not well investigated. The purpose of this study was to determine the test-retest repeatability of the MPM in persons with postoperative pain. Subjects: A convenience sample of 47 patients following gynecologic or orthopedic surgery at a university teaching and VA hospital was selected. Nearly half (N=24) were women. The mean age was 46 (SD=14) years. Methods: Patients were asked to indicate the areas on the MPM where they had pain over the past week. Patients were initially approached on the second post-operative day (T1) and had the MPM readministered 1-2 days later (T2). Results: The mean number of painful areas (NPA) selected at T1 was 4.1 (SD=3.0) and 4.3 (SD=3.5) at T2 (paired t-test, p > 0.05). The NPA ranged from 1-13 at T1 and 1-21 at T2. The intra-class correlation coefficient for NPA between T1 and T2 was 0.84 (p < 0.001) indicating excellent overall agreement. Of the 36 possible body areas, the six most common painful areas were the abdomen (51%), right hip (36%), groin (25%), right thigh (24%), left hip (22%), and low back (19%), reflecting the location of surgery. Kappa values for these areas between T1 and T2 were 0.70, 0.57, 0.43, 0.82, 0.62, and 0.50, respectively. Conclusion: The MPM is a repeatable measure of self-reported pain location in persons with post-operative pain.