Do patient and proxy agree? Long-term changes in multiple sclerosis physical impact and walking ability on patient-reported outcome scales.
BACKGROUND
Patient-reported outcome scales (PROs) are useful in monitoring changes in multiple sclerosis (MS) over time. Although these scales are reliable and valid measures in longitudinal studies in MS patients, it is unknown what the impact is when obtaining longitudinal data from proxies.


OBJECTIVE
The objective of this paper is to compare longitudinal changes in patient and proxy responses on PROs assessing physical impact of MS and walking ability.


METHODS
In a prospective observational study, data on the Multiple Sclerosis Impact Scale (MSIS-29 physical) and Multiple Sclerosis Walking Scale (MSWS-12) were obtained from 137 patient-proxy couples at baseline and at two-year follow-up. Demographic and disease-related variables explaining agreement or disagreement between patients and proxies were investigated using linear regression analyses.


RESULTS
Full agreement was found in 56% (MSIS) and 62% (MSWS) of the patient-proxy couples. Complete disagreement was very rare for both scales (2% MSIS, 5% MSWS). When patients were more positive than proxies, a higher age, longer disease duration, longer patient-proxy relationship and increased levels of depression, anxiety and caregiver burden in proxies were observed.


CONCLUSIONS
In the majority of the patient-proxy couples there was agreement. Proxies can serve as a valuable source of information, but caution remains essential when using scores from proxies.
Department of Neurology, VU University Medical Center, De Boelelaan 1117, PO Box 7057, 1007 MB Amsterdam, The Netherlands Judith.sonder@vumc.nl.
Judith M
JM
Sonder
Department of Neurology, VU University Medical Center, The Netherlands.
Lisanne J
LJ
Balk
Department of Neurology, VU University Medical Center, The Netherlands.
Libertje V A E
LV
Bosma
Department of Neurology, VU University Medical Center, The Netherlands.
Chris H
CH
Polman
Department of Neurology, VU University Medical Center, The Netherlands.
Bernard M J
BM
Uitdehaag
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000503:physiopathology / Q000523:psychology / Q000534:rehabilitation*; D011446:Prospective Studies; D019727:Proxy / Q000523:psychology*; D012044:Regression Analysis; D057566:Self Report; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016138:Walking / Q000502:physiology*; D055815:Young Adult
Multiple sclerosis; anxiety and depression; caregiver burden; outcome measurement; patient-reported outcome; proxy