Health outcome measures in an aging population : validity, reliability and interpretability

In Canada, older adults currently represent a record high proportion of about 15% of the population. Associated with aging is the increased prevalence of multiple morbidity, resulting in widely varied and complex health statuses among our aged. Identifying effective strategies to promote healthy aging and reduce comorbidity hinges on the ability to accurately measure health outcomes. This requires the use of valid and reliable instruments with associated reference statistics to enhance interpretability of test scores. In Chapter 2, I present a validity study of a patient-reported outcome measure, the Patellofemoral Pain and Osteoarthritis Outcome Scale (PFOOS). The PFOOS is designed to evaluate symptoms relating to patellofemoral (PF) pain and osteoarthritis. I recruited 54 adults aged 18+ with peri- or retro-patellar pain for ≥ 3 months, rated ≥3/10 on a numeric pain scale, aggravated by PF-loading tasks (e.g. squats). People with diffuse knee pain, history of total knee or hip replacement, or severe knee trauma in the past year were excluded. Recruitment was done through adverts to staff & students at an Australian University. Participants completed paper & online versions of the PFOOS, Anterior Knee Pain Scale and SF-36, and repeated the PFOOS in 1-2 weeks. Analysis included internal consistency (Cronbach’s α), test-retest & alternate forms reliability (ICC), and construct validation (hypothesis testing). ICCs were ≥ 0.79, Cronbach’s α ≥ 0.61. The PFOOS performed largely as hypothesized. Overall, the PFOOS demonstrated good validity & reliability in this sample. In Chapter 3, I report results of a cross-sectional study aimed to develop normative data for the de Morton Mobility Index (DEMMI). The DEMMI is a performance-based instrument that measures mobility across a spectrum from bed bound to functional independent mobility. A sample of 183 healthy, community-dwelling adults age 60+ were recruited. Mean DEMMI scores varied by age category, by living arrangement (independent vs. assisted living), and by use of mobility aid (p