A 28-year-old woman from Kerala presents with jaundice, dark urine, and pallor. On examination, splenomegaly is noted. Laboratory findings show Hb 8.5 g/dL, reticulocyte count 12%, indirect bilirubin 4.2 mg/dL, and a positive direct antiglobulin test (DAT). Peripheral blood smear shows spherocytes. She denies recent transfusions, infections, or drug use. What is the most appropriate next step in management?