Comparison of responses to SF-36 Health Survey questions with one-week and four-week recall periods.

OBJECTIVE

To compare the measurement properties of acute (one-week recall) and standard (four-week recall) versions of SF-36 Health Survey (SF-36) scale scores.

DATA SOURCES

SF-36 data collected from 142 participants (60% female, average age 39) in a clinical trial of an asthma medication: 74 patients randomized to the acute form and 68 to the standard.

DATA COLLECTION

The SF-36 was self-administered at the time of a clinic visit (before clinical examination) to synchronize with clinical measures of disease severity at three different time points during the clinical trial: -2 weeks (two weeks before randomization to treatment), baseline (week 0 or randomization), and +4 weeks (four weeks after baseline).

PRINCIPAL FINDINGS

The acute form yielded high-quality data; scales conformed to the assumptions of the summated ratings method used to score the standard SF-36; and scales had good distributional properties, were reliable, and had a factor content similar to the standard. The data indicated that while the acute form was more sensitive than the standard to change in health status associated with changes in acute symptoms, acute scale scores may not be comparable to national norms based on the standard, particularly for those scales that assess frequency of health events during a specified time period.

CONCLUSIONS

Results support the use of the acute form in its intended applications; however, further research is required to document the generalizability of greater sensitivity of the acute form to recent changes in health and to explore whether norms based on the standard can be used to interpret the acute scale scores.