GSTM1 and acute chest syndrome: The independent factors associated with ACS were average Hb rate <8 g/dL (OR = 4.96, 95% CI = 1.29–27.34, and P = 0.04), annual number of hospitalizations >3 (OR = 5.44, 95% CI = 3.59–8.21, and P = 0.003), average length of hospitalization >7 days (OR = 3.69, 95% CI = 3.59–8.21, and P = 0.003), and a pathological transthoracic echocardiography (TTE) (OR = 13.77, 95% CI = 2.07–91.46, and P = 0.003).