Prevalence and factors associated with impaired six-minute walk test in relatively well children with sickle cell disease at a public tertiary hospital – Kenya

Abstract

Objective: To determine the prevalence of impaired functional exercise capacity using the six-minute walk test (6MWT), in children with Sickle cell disease and to determine factors associated with this impaired exercise capacity.
Study design, setting and duration: A descriptive cross-sectional study carried out at the Paediatric Haematology clinic of a public tertiary referral facility (Kenyatta National Hospital) in Kenya. Consecutive sampling was carried out between October 2020 - January 2021.
Subjects: Children aged 6-13years with Sickle cell disease confirmed by Haemoglobin (Hb) electrophoresis. Informed consent from parent/guardian and assent from child.
Outcomes: Impaired cardiac function defined as either having abnormal heart rate for age (tachycardia) or rhythm, displaced apex beat, abnormal heart sounds or signs of impending cardiac failure; impaired respiratory function defined as a respiratory rate higher than the expected for age and hypoxia defined as an SPO₂ of less than 95% and rate of perceived exertion (RPE) as weak, moderate, or strong
Results: Greater than 90% of the patients had hypoxia at rest (SPO2 less than 92%) with 21.2% having tachypnoea and 42.4% having tachycardia 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, hydroxyurea use and age-specific heart rate, respiratory rate, and body mass index Z-score (adjusted odds ratio 1.4(1.1-1.9), p=0.034).
Conclusion: A 6WMT performed at earlier ages may be useful in screening and predicting the degree of cardiorespiratory functional impairment in children with Sickle cell disease.