Identifying Latent Outcome Measures in Inpatient Physical Therapy

Like all health care practitioners, physical and occupational therapists provide services to their patients that are intended to increase patient health and well-being. But because patient health and well-being are inherently latent, therapists are often forced to utilize indirect methods for measuring the effectiveness of their practices. These indirect methods usually involve gathering data on multiple indicators of therapy effectiveness. The problem with this approach is that there are usually multiple indicators for each latent phenomenon, and each of those indicators may give contradictory findings. As a result, the exact relationship between each indicator and the underlying phenomenon is often unclear. In this paper, we apply factor analysis to data on inpatient physical therapy following total knee replacement surgery (TKR) at a Midwestern rehabilitation institute. Our goal is to not only determine how many different latent measures of patient well-being are inherent in this type of therapy, but also to identify which (and how much) each of the empirical indicators commonly used to measure patient progress contribute to each of these underlying factors. The results of our analysis indicate that there are two underlying rehabilitation factors. One of these underlying measures is explained primarily by the flexion measures taken by the staff, while the other latent factor is explained by the remaining empirical indicators. Thus, it appears that patient progress in post-TKR therapy is really a two-fold phenomenon. As such, process improvement initiatives intended to quantify and increase the quality of care provided to patients must be adapted to take this finding into account.