['Pre-donation of autologous blood prior to spine fusion for adolescent idiopathic scoliosis (AIS) has been used in deformity surgery. The effect of pre-donation on pre-operative hematocrit (Hct) remains debated. Multiple factors may influence pre-operative Hct including intravascular volume status, patient factors, and timing of pre-operative blood donation. The purpose of this study was to determine if pre-donation significantly lowers pre-incision Hct in AIS patients.', "A retrospective cohort study of a Level-1 prospective randomized trial was conducted. 125 patients from the homogeneous population were included. AIS patients undergoing a posterior only spinal fusion for AIS were separated into two groups based on their pre-operative blood donation history. Demographic variables, pre-incision Hct, and transfusion rates were compared between the two groups using the Student's T-test.", 'Pre-donation and non pre-donation groups had 28 and 97 patients, respectively. Pre-donation group was 75% female (21F, 7M) and non pre-donation group was 78% female (76F, 21M). There was no difference between pre-donation and non pre-donation groups in mean age (15.6 ± 2.2 vs 14.8 ± 2.2, p = 0.081), BMI (23.1 ± 4.2 vs 21.7 ± 5.3, p = 0.219), and pre-incision Hct (32.8 ± 3.4 vs 33.8 ± 3.1, p = 0.628). The overall transfusion rates were equivalent (32.1± 48.0% vs 25.8 ± 44.0%, p = 0.509), however, the rate of allogenic transfusion for the pre-donation group was significantly lower (3.6 ± 18.9% vs 25.8 ± 44.0%, p = 0.011).'] Does pre-Operative Autologous Blood Donation Affect Pre-Incision Hematocrit in Adolescent Idiopathic Scoliosis Patients . A Retrospective Cohort of a Prospective Randomized Trial?