A 25yr old female presents with anemia and jaundice since 2 years. On examination her spleen is enlarged. Peripheral smear showed presence of spherocytes. Which of the following investigation is used in diagnosing this condition?

Young female with 2 years history of anemia and peripheral smear showing spherocytes points towards the diagnosis of autoimmune haemolytic anemia (AIHA). In the above question age, gender and history of patient ours AIHA. Most impoant differential diagnosis for AIHA is hereditary spherocytosis. Diagnosis of hereditary spherocytosis is established by osmotic fragility test. Hereditary spherocytosis is an autosomal dominant inherited disorder resulting from molecular abnormalities in the cytoskeleton of red cell membrane. Diagnosis of hereditary spherocytosis is established clinically from Positive family history and splenomegaly Blood film showing spherocytes and reticulocytes Increased osmotic fragility Negative coombs test