A 2019 publication found proxy respondents for adults who had a stroke reported more severe symptoms on the PROMIS Global scale that patient self-report.
Lapin, B.R., Thompson, N.R., Schuster, A. et al. Patient versus proxy response on global health scales: no meaningful DIFference. Qual Life Res (2019).
Yes and there are several studies showing that including:
Hays, R. D., Vickrey, B., Hermann, B., Perrine, K., Cramer, J., Meador, K., Spritzer, K., & Devinsky, O. (1995). Agreement between self reports and proxy reports of quality of life in epilepsy patients. Quality of Life Research, 4, 159-168.
PROMIS did not develop measures intended to be completed by caregivers or other people on behalf of adult respondents. The literature suggests there may be differences between how "patients" respond compared to proxies, especially for domains that are less apparent to others, such as pain, fatigue and emotional distress.