Validation of self-reported fall events in intervention studies

Abstract

Objective: To determine if self-reported data recalling at least one fall over a sixmonth recall period could be used as a reliable measure of falls by comparing retrospective self-report with a ‘gold standard' method of reporting these events using a prospective calendar-reported method. Design: Prospective study. Setting: Community-dwelling older people living in New South Wales (NSW) and Queensland in Australia. Subjects: A stratified sample of 264 randomly selected participants from a concurrent randomized controlled trial (RCT) of preventive health assessment for people over the age of 70 years. Interventions: Intervention and control group participants in the RCT kept a calendar of fall events for a six-month validation substudy. At the end of six months, participants were asked to retrospectively report their falls over the six-month period. Main results: Results indicated that percentage agreement between retrospective self-report and the calendar report of falls was 84%, however, sensitivity was 56% (95% confidence interval (CI) 44.1−67.5). Ten participants (4%) gave false positive self-reports of falls, and 33 (13%) participants gave false negative self-reports of falls. Therefore, retrospective self-reported fall rates were likely to involve under-reporting of falls. Significant differences were found in the sensitivity of retrospectively selfreported falls reported by the intervention group participants (sensitivity=71%; 95% CI 56.6−85.5) compared with the control group (sensitivity=40.5%; 95% CI 24.7−56.4, P =0.008). Validity of self-reported injuries as a result of a fall was less accurate (71% agreement; sensitivity 24% (95% CI 16.0−33.6). Conclusions: As recall of falls was more accurate in the intervention group than in the control group, it could appear that the intervention had the effect of increasing falls compared to the control group. Using these results, a method was devised to weight self-reported retrospective data to compensate for the poorer recall demonstrated in the control group, so that a more accurate estimate of falls could be derived from the self-reported data.