Introduction
Sickle cell anemia (SCA) is the most common monogenic disease in the world, predominant among people of African descent and brown skin. It is characterized by the occurrence of sickle cells due to the mutant presence of hemoglobin S (HbS).1 The altered erythrocytes present difficulty in circulating in the blood, which causes vaso-occlusive phenomena and infarction in the affected area. In addition, this altered physiology causes permanent damage to tissues and organs, with the cardiorespiratory system being the target of acute and chronic manifestations.2 Thus, lung function and cardiovascular impairments changes favor a sedentary lifestyle, reduced functional capacity and worsening quality of life (QOL).3,5,6 Different tests that assess functional capacity are available. Hostyn4 et al. (2013), showed higher number of hospitalizations in children and adolescents with SCA (genotype Hb-Sβ0–thalassemia) who walked shorten distance at the 6-minute walk test (6MWT). This test has been widely used, however there are some limitations as self-paced test, floor effect. Thus, the Modified Shuttle Walk Test (MSWT) in patients with SCA can be an alternative, considering it has already been described in children and adolescents’ other chronic conditions.7 -10
The MST is simple and low cost, needs corridor of 10 meters (m), limited by symptoms, externally paced, and allows the volunteer walk or run.4 This test is appropriated to assess exercise intolerance in individuals with different severity status. Additionally, the MSWT can be used to exercise prescription. 11 The sit and stand movement are considered fundamental for mobility and functional independence. This movement is part of several activities of daily living (ADL) and the literature has already described the 5-repetition sit-to-stand test (5STS-test) as a simple and low coast test to measure lower limb strength, balance control, risk of falling and exercise capacity.13 Thus, the 5STS-test is another alternative to assess different aspects of functional capacity compared to MSWT. This study aims to evaluate and compare the functional capacity, pulmonary function and quality of life of children and adolescents with SCA with their healthy peers and to analyze the reproducibility of the functional capacity tests on the sickle cell anemia group. The hypotheses are that SCA individuals have reduced exercise capacity, lung function and quality of life.