OBJECTIVES: While the importance of evaluating physical functioning (PF) due to weight loss is well recognized, a patient-reported outcomes instrument has not been qualified by the US Food and Drug Administration for this use. This study evaluated the content validity of two Patient-Reported Outcomes Measurement Information System (PROMIS®) short forms for PF (8b and 10a) in overweight and obese adults. Both measures self-report PF capability and include items on upper and lower extremities and activities of daily living.
METHODS: Four sets of individual interviews were conducted among adults with and without T2DM in the US using a semi-structured interview guide. Interviews began with open-ended concept elicitation. Cognitive debriefing was conducted for the 8b in three sets of interviews and for the 10a in the final set.
RESULTS: Forty-three individuals with mean BMI of 36.2 kg/m2 (range: 25.7-48.7) and age of 44.8 years (range: 18-70) were interviewed. Participants were mostly white, non-Hispanic, and college educated.
The most common reported impacts of excess weight related to PF included reductions in energy, difficulties with flexibility (bending down, getting off the floor), mobility (walking, stairs), recreational activities (sports, exercise), and physical labor at home or work (housework, yardwork). Participants with higher BMIs reported greater PF limitations.
While the concepts addressed by the 8b were generally deemed relevant, several concerns were noted, including duplicative items, vague or potentially confusing concepts, and omission of specific activities impacted by weight (going up stairs, bending/kneeling, vigorous activities/sports).
Participants indicated the 10a was comprehensive (no major concepts missing) and items were distinct, easily understood, and easy to answer. All participants stated the 10a provided an accurate assessment of their PF.
CONCLUSIONS: The concepts addressed by the 8b were generally relevant; however, the 10a may be more appropriate for the evaluation of PF among obese individuals.
