Recall bias did not affect perceived magnitude of change in health-related functional status.

BACKGROUND AND OBJECTIVE

It was hypothesized that within an invasively treated group and within a group that improved in angina pectoris no difference in effect size would occur between prospective and retrospective measures. Furthermore, it was hypothesized that assessment of perceived change at post-test may be invalid because of recall bias and present-state bias.

STUDY DESIGN AND SETTING

Effect sizes (as standardized response means) were used as indicators of magnitude of change. Linear structural equation analysis (with LISREL) was used to investigate the relationship between the estimates of recall accuracy and retrospectively assessed change.

RESULTS

No significant differences were found between prospective and retrospective measures of change over time in health-related functional status. Recall bias was not associated with retrospective measurement of change within a 12-week interval. An expected present-state effect was found in a structural equation model.

CONCLUSION

Prospective and retrospective indices of magnitude of change were similar between groups receiving treatment of known efficacy. Recall bias seems to be an acceptable risk in short-term follow-up studies.