A 20 year old female presenting with anemia, mild jaundice for 2 years, peripheral smear showing spherocytes, the best investigation to be done is:

Spherocytes in adult patient indicates presence of autoimmune haemolytic anemia and hence Coomb's test should be performed. Presence of spherocytes alone is not sufficient for the diagnosis of hereditary spherocytosis. Evidence of hereditary nature of the disease is also required. Increased osmotic fragility merely reflects the presence of spherocytes and does not distinguish hereditary spherocytosis from other spherocytic hemolytic disorders.