Prevalence and Factors Associated With Impaired Six Minute Walk Test in Children With Sickle Cell Disease at the Kenyatta National Hospital

Abstract

Background: The six-minute walk test is a simple, reproducible, reliable and valid tool for evaluation of baseline functional capacity in chronic diseases like sickle cell disease (SCD). Objectives: Primarily determine the prevalence of impaired functional exercise capacity using the six-minute walk test (6MWT), in children 6 to 12 years of age with SCD on follow-up at the haematology clinic at Kenyatta National Hospital(KNH) and secondarily to determine demographic, anthropometric and physiologic factors associated with impaired exercise capacity in children with SCD. Methodology: A cross-sectional study design that recruited 99 children with SCD from the paediatric haematology clinic in KNH by consecutive recruitment. Data was collected by means of a questionnaire, pre and post 6MWT walk vitals form and the 6MWT lap counter worksheet. The 6MWT was conducted as per the American Thoracic Society (ATS) guidelines. Impaired 6MWT was defined as a distance less than 80% of predicted distance based on Tunisian predictive reference equations. Data analysis: Data was analysed using R (V3.4.3, R core team, 2017). The impaired 6MWT was presented as a prevalence with 95% confidence interval. A multivariable logistic regression model was used to determine demographic, anthropometric and physiologic factors associated with the impaired 6MWT. A p-value of <0.05 was considered to be significant Results: The prevalence of impaired 6MWT was found to be 69.7% ( 95% CI 60.1 - 77.9%).Age was independently associated with impaired 6MWT when adjusted for Gender, Haemoglobin level, use of hydroxyurea and age specific heart rate, respiratory rate and body mass index Z-score – (adjusted odds ratio 1.4(1.1-1.9), p value 0.034). Conclusion: In this study, the prevalence of impaired 6MWT was very high at almost 70%. The only factor associated with the walk test was Age. Simple tests like 6MWT can be used to provide data on the degree of functional impairment which could be used to suggest cardiorespiratory compromise in patients with chronic diseases like SCD