METHODS
In this case-control study, we recruited patients with SCD with or without a physician diagnosis of asthma and healthy African American controls between 6 and 18 years of age. Inclusion/exclusion criteria: Inclusion criteria were a diagnosis of sickle cell disease (HbSS, HbSβ-thalassemia+, HbSβ-thalassemia0, HbSC, HbSO Arab) confirmed by hemoglobin analysis. Age criteria was 6 to 18 years of age. Exclusion criteria were preterm birth (born at < 37-week gestation) or an inability to complete study activities. Participants completed study activities only if they were at baseline health without respiratory or SCD related complications occurring within the previous 4 weeks. Healthy African American controls between the ages of 6 to 18 years were also recruited but were excluded from the study for a diagnosis of asthma, any episodes of wheezing leading to shortness of breath in the previous 12 months or presence of a bronchodilator response (≥ 12% increase in FEV1 or FVC post-bronchodilator).
This study was approved by our institutional IRB and informed consent and assent, where applicable, were obtained for all participants. A thorough history was obtained, and a physical examination completed at the time of study participation. A review of the participants’ medical charts was conducted to obtain data regarding episodes of ACS, severe pain crises requiring an inpatient stay, a physician-documented diagnosis of asthma and other co-morbidities. All participants performed pulmonary function tests (PFT) including MBW (Eco Medics Exhalyzer D, software version 3.1.6) using nitrogen as the washout gas, plethysmography (Morgan Scientific, ComPAS software version 1.10.2642.4440), and pre- and post- bronchodilator spirometry (Morgan Scientific, ComPAS software version 1.10.2642.4440). Blood was obtained from healthy controls at the time of the study visit as well as in those SCD subjects with no laboratory studies in the previous 3 months