ROP - Retinopathy of prematurity; T - t-statistic; U - Mann-Whitney U; χ2 - Chi-square; PRBC: Packed red blood cell; BPD - Bronchopulmonary dysplasia; Hb - Hemoglobin; RDS - Respiratory distress syndrome; TLC - Total leucocyte count; ALC - Absolute lymphocyte count; ANC - Absolute neutrophil count; AMC - Absolute  monocyte count. The gene discussed is GSTM1; the disease is retinopathy of prematurity.