Single-change items did not measure change in quality of life
Adam J Rose1, Naomi C Sacks, Abhijit P Deshpande
1Department of Health Policy and Management, School of Public Health, Boston University, Boston, MA, USA. adamrose@bu.edu
Objectives:
The aim of this study was to demonstrate validity for the two items in the Veterans RAND 36 Item Health Survey (VR-36) that attempt to measure the change in health-related quality of life (HRQOL) over 1 year, using serial administrations of the full instrument as a gold standard.
Study Design And Setting:
A total of 1,117 subjects in the Veterans Health Study completed the VR-36 instrument at study inception and 1 year later. Using nonparametric correlation and factor analyses, we compared the single-change items (SCIs) with 1-year changes in the physical component score (PCS) and mental component score (MCS), the summary scores of the VR-36.
Results:
We found low correlations between the SCI and longitudinal changes in the PCS (0.21) and MCS (0.18) and moderate correlations between the SCI and the current PCS (0.50) and MCS (0.41). Factor analyses confirmed that the SCI loaded highly with current HRQOL.
Conclusions:
The two SCIs contained in the VR-36, which are intended to measure changes in health over the past year, are more highly correlated with current self-reported HRQOL. In this instrument, single-item measurements of health status change cannot be substituted for changes in serial measures of HRQOL.