Clinical validation of the Walking Impairment Questionnaire in patients with peripheral arterial disease: defining high and low walking performance values by Stephen P. Sagar A thesis submitted to the Department of Community Health and Epidemiology In conformity with the requirements for the degree of Master of Science Queen‟s University Kingston, Ontario, Canada (August 2011) Copyright ©Stephen P. Sagar, 2011 Abstract Objective: The validity of the Walking Impairment Questionnaire (WIQ) as a clinical tool for use by clinicians in the conservative management of patients with peripheral arterial disease (PAD) has not been well established. The objective of this study was to determine the validity of the WIQ as a tool to identify high and low walking ability (performance) in patients with PAD. Methods: We conducted a cross-sectional study and enrolled 132 new and existing PAD patients who consecutively attended the vascular clinic at Kingston General Hospital between May 2010 and May 2011. Patients with an Ankle Brachial Index ≤0.9 were approached for study inclusion. Participants were excluded if they had (a) severe ischemia requiring intervention; (b) comorbid conditions that limited walking (angina, congestive heart failure, chronic obstructive pulmonary disease or severe arthritis); (c) wheel chair, cane or walker requirement; (d) non-compressible arteries; and/or (e) severe cognitive impairment. Walking performance was assessed with the Walking Impairment Questionnaire (surrogate measure) and a standardized graded treadmill test (gold standard measure). Other study variables were obtained via questionnaire (age, sex, comorbid conditions and smoking status) or direct measurement (weight, height, waist circumference). Results: 123 patients completed the treadmill test (70.7% males, mean age of 66.5 and mean ABI of 0.6 with range 0-0.9). The scores on the WIQ ranged from 0 to 100 and absolute claudication distance (ACD) ranged from 0.03 to 0.98 miles. All WIQ subscale and overall scores were positively and moderately associated with the ACD (r values 0.63 i to 0.68, p<0.05). Based on the area under the curve of the receiver operating characteristics curve analysis, an overall WIQ score of 42.5 or less identified low performers (sensitivity 0.9, specificity 0.7, area under the curve 0.89) while a combined distance and stair score of 75.5 or more identified high performers (sensitivity 0.4, specificity 0.9, area under the curve 0.81). Conclusions: Based on these findings, the WIQ, an easily administered self-report questionnaire, and the cutoffs identified could be used to quantify and classify walking ability in PAD patients, making this a potentially useful tool for clinicians to manage PAD patients. ii Co-Authorship This thesis is the original work of Stephen Sagar under the supervision of Drs. Joan Tranmer (primary supervisor), Peter Brown and William Pickett. The research objectives, design, analysis, and interpretation of findings were the sole work of Stephen Sagar with input from Drs. Tranmer and Pickett. Writing of the manuscript and writing of thesis chapters was performed by Stephen Sagar with supervision by Drs. Tranmer and editorial feedback from Drs. Brown and Pickett. iii Acknowledgements I would like to acknowledge the hard work and guidance of my supervisors, Drs. Joan Tranmer (Primary), Peter Brown and William Pickett. Your constructive feedback and positive attitude have helped me learn and develop both as a scientist and an individual. Your focus on personal health, personal development and work/family balance is something to which I aspire. I would like to thank the faculty, staff and students of the department of Community Health and Epidemiology for providing a positive learning environment. I would like to acknowledge my lab-mates. Thank you for acting as a sounding board for my sometimes ridiculous ideas and for providing a constant source of entertainment and lifting my spirit when I was down. Thank you and best wishes for your future work to Lynda Reid for your tremendous help with patient testing and data entry. I would like to acknowledge Queen‟s University for providing me with an intellectually stimulating environment over the past six years. I would also like to thank QFA, QSC, Camp Outlook, the Queen‟s cycling and triathlon teams and Beat‟em and Treat‟em for helping me grow and develop as an individual. I believe the skills and lessons I learnt through these extracurricular activities have prepared me to face, and possibly thrive in, the world outside the Queen‟s bubble. On a technical note, I would like to thank the Sagarsaurus Rex, the Veloci-Sagar, two of my bikes, for providing motivation to get through my days work and keeping me physically active. Thanks also to my commuter bikes for ensuring I made it to work day- iv in and day-out through rain, wind and snow. I would also like to acknowledge the internet for allowing me to stream television shows and not waste time on commercials. Finally I would like to extend a special thanks to my friends and family (I will thank each of you in person) for your continued encouragement and your ability to make me laugh. To my parents: thank you for your support throughout my education and for helping me believe I could accomplish anything. You have helped make me the person I am today and for that I am truly thankful (although you can ease up on the puns). v Table of Contents Abstract ............................................................................................................................................. i Co-Authorship ................................................................................................................................. iii Acknowledgements ......................................................................................................................... iv Table of Contents ............................................................................................................................ vi List of Figures ................................................................................................................................. ix List of Tables ................................................................................................................................... x List of Acronyms ............................................................................................................................ xi Chapter 1 General Introduction ........................................................................................................ 1 1.1 Background and rationale ...................................................................................................... 1 1.2 Objectives and relevance ....................................................................................................... 2 1.3 Study design ........................................................................................................................... 3 1.4 Thesis organization ................................................................................................................ 3 1.5 Student Contributions ............................................................................................................ 4 References ................................................................................................................................ 5 Chapter 2 Literature Review ............................................................................................................ 7 2.1 Key terms and definitions ...................................................................................................... 7 2.2 PAD........................................................................................................................................ 8 2.2.1 Prevalence ....................................................................................................................... 8 2.2.2 Diagnosis and assessment ............................................................................................... 8 2.2.3 Clinical presentation, prognosis and natural history ....................................................... 9 2.2.4 Risk Factors................................................................................................................... 10 2.2.5 Treatment ...................................................................................................................... 11 2.2.6 Assessment of walking performance ............................................................................ 12 2.2.6.1 Walking tests ...................................................................................................... 12 2.2.6.2 Self report assessment ........................................................................................ 15 2.2.6.3 Validation of the Walking Impairment Questionnaire ....................................... 19 2.3 Summary .............................................................................................................................. 22 References .............................................................................................................................. 25 Chapter 3 Methods ......................................................................................................................... 28 3.1 Overview .............................................................................................................................. 28 vi 3.2 Ethical approval ..................................................................................................................