title: The impact of response shift on perceived disability two years following rotator cuff surgery.
abstract: BACKGROUND
  Understanding how patients appraise their health-related problems is important for an accurate assessment of recovery over time. It has been proposed that the response shift phenomenon has an impact on self-report measures, and this may subsequently affect measurement of true treatment effects. The objective of the present study was to explore the impact of response shift on the subjective perception of disability following rotator cuff surgery.
  
  
  METHODS
  We conducted a repeated-measures study of the outcome following surgical decompression or repair of the rotator cuff. The American Shoulder and Elbow Surgeons (ASES) questionnaire was used in a thentest design to measure recalibration response shift two years following surgery. Disability was measured with a disease-specific measure. Objective findings consisting of the range of motion and strength were recorded preoperatively and postoperatively. Parametric and nonparametric univariate and multivariate analyses were performed. The contribution of recall bias was estimated by assessing agreement between pretest and thentest scores on the basis of the percentage of agreement and the Spearman correlation coefficient.
  
  
  RESULTS
  One hundred and seven patients (forty-one women and sixty-six men; mean age, fifty-seven years) participated in the study. Seventy-two patients had decompression surgery and forty-four underwent a rotator cuff repair; nine patients had both procedures. A significant response shift was observed in the pain domain (p < 0.0001) and not in the functional ability domain of the ASES (p = 0.58). Three distinct patterns of response shift were observed. Univariate analyses showed that satisfaction with the result of the surgery, the range of motion, strength, age, and response shift were associated with disability. The final multivariate analysis showed that disability at two years following the surgery was affected by the range of motion (p < 0.0001), satisfaction (p = 0.006), age (p = 0.02), and response shift (p = 0.03).
  
  
  CONCLUSIONS
  The response shift phenomenon exists in patients who have undergone surgery for rotator cuff disorders and has different patterns related to overrating or underrating of preoperative pain. A recalibration response shift characterized by overrating of preoperative pain was associated with lower levels of residual disability at two years following the surgery.
authors.affiliation: Holland Orthopaedic and Arthritic Centre, Sunnybrook Health Sciences Centre, 43 Wellesley Street East, Toronto, ON M4Y 1H1, Canada. Helen.razmjou@Sunnybrook.ca
authors.forename: Helen
authors.initials: H
authors.lastname: Razmjou
authors.forename: Carolyn E
authors.initials: CE
authors.lastname: Schwartz
authors.forename: Richard
authors.initials: R
authors.lastname: Holtby
mesh_terms: D000203:Activities of Daily Living; D000223:Adaptation, Psychological; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000523:psychology; D011788:Quality of Life / Q000523:psychology*; D016059:Range of Motion, Articular; D020127:Recovery of Function; D017006:Rotator Cuff / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D012647:Self-Assessment; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D055815:Young Adult