Introducing a new definition of a near fall: intra-rater and inter-rater reliability

Near falls (NFs) are more frequent than falls, and may occur before falls, potentially predicting fall risk. As such, identification of a NF is important. We aimed to assess intra and inter-rater reliability of the traditional definition of a NF and to demonstrate the potential utility of a new definition. To this end, 10 older adults, 10 idiopathic elderly fallers, and 10 patients with Parkinson's disease (PD) walked in an obstacle course while wearing a safety harness. All walks were videotaped. Forty-nine video segments were extracted to create 2 clips each of 8.48 min. Four raters scored each event using the traditional definition and, two weeks later, using the new definition. A fifth rater used only the new definition. Intra-rater reliability was determined using Kappa (K) statistics and inter-rater reliability was determined using ICC. Using the traditional definition, three raters had poor intra-rater reliability (K<0.054, p>0.137) and one rater had moderate intra-rater reliability (K=0.624, p<0.001). With the traditional definition, inter-rater reliability between the four raters was moderate (ICC=0.667, p<0.001). In contrast, the new NF definition showed high intra-rater (K>0.601, p<0.001) and excellent inter-rater reliability (ICC=0.815, p<0.001). A priori, it is easy to distinguish falls from usual walking and NFs, but it is more challenging to distinguish NFs from obstacle negotiation and usual walking. Therefore, a more precise definition of NF is required. The results of the present study suggest that the proposed new definition increases intra and inter-rater reliability, a critical step for using NFs to quantify fall risk.