Study DesignRetrospective comparative study.ObjectivesWe aimed to characterize the frequency of perioperative laboratory tests for posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS) and to assess whether test results affected clinical management.Summary of Background DataPerioperative laboratory tests for PSF including complete blood count, coagulation laboratory tests, basic metabolic panels (BMPs), and type and screen, are commonly ordered based on providers' discretion or existing order sets. Studies have shown unnecessary laboratory tests as financially and physically costly in adults; however, no studies have examined the necessity of common perioperative laboratory tests in pediatric spinal deformity surgery.MethodsRetrospective review of patients aged 10-18 years who underwent PSF for AIS at our center in the past three years. The clinical utility of perioperative laboratory tests was assessed based on detected incidence of anemia, blood transfusions, hematology/endocrinology/nephrology consultations, insulin administration, and postponed/canceled surgeries.ResultsA total of 234 patients were included (mean age 14.4 1.8 years, 75% female). Of 105 (44.9%) patients with preoperative coagulation laboratory tests, 21 (20%) had abnormal results; however, none had subsequent hematology consultations or canceled/postponed surgeries. Postoperatively, only 5 (2.1%) patients and 30 (12.8%) patients had hemoglobin values less than 8 g/dL on postoperative day (POD) 1 and 2, respectively. Multivariate analysis identified POD1 hemoglobin <= 9.35 g/dL as the only predictor of hemoglobin <8 g/dL on POD2. Overall, there were 8 (3.4%) indicated blood transfusions postoperatively. Costs of unnecessary laboratory tests averaged $95.27 (range $49.72 to $240.27) per patient.ConclusionsMany perioperative laboratory orders may be unnecessary in pediatric spinal deformity surgery, subjecting patients to extraneous costs and needlesticks. In particular, preoperative coagulation laboratory tests, perioperative BMPs, and additional postoperative CBCs for those with hemoglobin >9.35 on POD1 may not be warranted.Level of EvidenceLevel III, retrospective cohort study.