The BODY-Q Stretch Marks Scale: A Development and Validation Study

BACKGROUND: Stretch marks are common permanent dermal lesions that can cause psychosocial distress. A number of treatment modalities are available, with the majority targeted towards collagen production. OBJECTIVES: To develop and field test a new BODY-Q scale to measure appearance of stretch marks in order to provide a means to incorporate the patient perspective into future treatment studies. METHODS: We previously described the development of the BODY-Q conceptual framework, which involved a literature review, 63 patient interviews, 22 cognitive interviews and input from 9 experts, and the international field-test study that involved 403 weight loss and 331 body contouring patients. To develop the Stretch Marks scale, we reexamined appearance codes from the original interviews. The scale was field tested in an international study. Rasch measurement theory (RMT) analysis was used to refine the scale and examine measurement properties. RESULTS: The Stretch Marks scale was completed by 630 participants, who provided 774 assessments. After dropping 3 items, the data fit the Rasch model (P = 0.56). Items (eg, length, width, amount, location, up close) mapped out a well-targeted clinical hierarchy. All items had ordered thresholds and good item fit. There was no evidence of differential item functioning (bias) by gender, age group or language (English vs Danish). The scale evidenced high reliability (ie, person separation index = 0.94, Cronbach's alpha = 0.97). For construct validity, the mean score correlated with the total number of body areas with stretch marks, higher BMI before bariatric surgery, and other BODY-Q scales. CONCLUSIONS: This scale could be used to measure the impact of innovative treatments for stretch marks.