Bariatric Times

APR 2018

A peer-reviewed, evidence-based journal that promotes clinical development and metabolic insights in total bariatric patient care for the healthcare professional

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20 Original Research Bariatric Times • April 2018 Further Psychometric Validation of the BODY-Q: Ability to Detect Change Following Bariatric Surgery Weight Gain and Loss by ANNE F. KLASSEN, STEFAN J. CANO, MANRAJ KAUR, TRISIA BREITKOPF, and ANDREA L. PUSIC Health Qual Life Outcomes. 2017;15(1):227. ABSTRACT Background: Recent systematic reviews have identified that current patient-reported outcome (PRO) instruments have content limitations when used to measure change following bariatric surgery. The aim of this study was to measure change after bariatric surgery using the BODY-Q, a PRO instrument designed for weight loss and body contouring. Methods: The BODY-Q is composed of 18 independently functioning scales and an obesity-specific symptom checklist that measure appearance, health-related quality of life (HR-QOL) and experience of healthcare. The sample for this study included patients who were exploring or seeking bariatric surgery in Hamilton, Canada at the time of the BODY-Q field-test study and who agreed to further contact from the research team. These patients were invited to complete 12 BODY-Q scales and the symptom checklist between June 7, 2016 and November 29, 2016. Data were collected online via Research Electronic Data Capture (REDCap) and via postal surveys. Clinical change was measured using paired t-tests with effect sizes and standardized response means. Results: The survey was completed by 58 of 89 (65%) pre-bariatric participants from the original BODY-Q field-test sample. The non-participants did not differ from participants in terms of age, sex, ethnicity, body mass index (BMI) or initial BODY-Q scale scores. Participants who had undergone bariatric surgery had a mean BMI of 49 (SD = 7) at Time 1 and 35 (SD = 7) at Time 2. Time since bariatric surgery was on average two years (range 0.4 to 3 years, SD = 0.5). Percentage total weight loss ranged from 12 to 51 (mean 31, SD = 9). The difference in the proportion of patients to report an obesity-specific symptom on the BODY-Q checklist was significantly lower at follow-up for 5 of 10 symptoms. Participants improved on BODY-Q scales measuring appearance (abdomen, back, body, buttocks, hips/outer thighs, and inner thigh), body image and physical function (p < 0.001 on paired t-tests), and social function (p = 0.002 on paired t-test). These changes were associated with moderate to large effect sizes (0.60 to 2.29) and standardized response means (0.47 to 1.35). Conclusion: The BODY-Q provides a set of independently functioning scales that measure issues important to patients who undergo weight loss. BODY-Q scales were responsive to measuring clinical change associated with weight loss two years after bariatric surgery. KEYWORDS Patient-reported outcomes, BODY-Q, responsiveness, clinical change, bariatric surgery, obesity, quality of life, appearance, satisfaction BACKGROUND Evidenced-based, patient-reported outcome (PRO) data is needed for bariatric surgery. 1–4 PRO instruments measure outcomes that matter to patients (e.g., symptoms, health- related quality of life [HR-QOL]), by asking them directly. 5 Such instruments are being used worldwide to inform patient care, as quality metrics, in audit studies and in comparative effectiveness research. 6–9 Some countries (e.g., United Kingdom, Netherlands, Sweden) use PRO instruments at a national level to compare providers or in clinical registries. 8,9 Outcome measures should be fit for purpose, i.e., capture the concepts of interest (e.g., physical function) in the context of use (e.g., patients attending a bariatric surgery clinic). 5 A number of recent systematic reviews have pointed out limitations in the content of current PRO instruments measuring HR-QOL in bariatric surgery research. 2–4 For example, the most common PRO instrument used in bariatric research is the generic Short Form-36 (SF-36) http://www.qualitymetric.com. This instrument has been critiqued for failing to measure a range of concepts important to patients undergoing weight loss (e.g., sexual function, self-esteem, appearance). 10 The most common obesity-specific tools used in bariatric research include the Impact of Weight on Quality of Life-Lite (IWQOL-Lite), 11,12 and Moorehead- Ardelt Quality of Life Questionnaire (MAQOL). 13 These instruments measure a range of obesity-specific concepts. The IWQOL-Lite, for example, measures physical function, self-esteem, sexual life, public distress, and work, 12 while the MAQOL has a total of six items covering self- esteem, physical, social, work, sexual, and eating behavior. 13 A limitation of these obesity-specific instruments is that their measurement model (classical test theory; CTT) lacks evidence that the summed scores provide meaningful measurement. 14,15 For example, in the CTT approach, it is considered legitimate to provide a total score for a PRO instrument that adds up scores for scales (IWQOL-Lite) or items (MAQOL). This approach to measurement is not helpful in clinical trials because it can mask effects of treatment, 14,15 for example, when patients who undergo weight loss improve on some scales or items (e.g., physical function as they lose weight) and not others (e.g., body image because of the development of excess hanging skin). The BODY-Q 16 represents a new generation PRO instrument that was developed using a modern psychometric approach called Rasch Measurement Theory (RMT). 17 In RMT, scales that compose a PRO instrument are each designed to measure and score a unidimensional construct (no total score). In scale development, data that meet the requirement of the Rasch model provide interval-level measurement. 15 When a scale has high content validity and is targeted to measure a concept as experienced by a sample, accurate tracking of clinical change can be achieved. 15 The aim of the present study was to measure clinical change for 13 BODY-Q scales/checklist that measure appearance (of upper arms, abdomen, back, body, buttocks, inner thighs and hips/outer thighs) and HR- QOL (body image, obesity-specific symptoms and psychological, social, sexual, and physical health) following bariatric surgery for participants from the BODY-Q field-test study who were recruited from the St Joseph's Healthcare Hamilton bariatric program in Canada. METHODS BODY-Q. We previously described the development of the BODY-Q. 16

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