A 23 years old asymptomatic female has MCV-70fl, ferritin - 100g/L, Hb-10gm%. Which of the following is the most likely cause?

This patient presenting with mild degree of microcytic anemia (MCV=70) with normal ferritin levels (100pg/L) suggesting a diagnosis of thalassemia trait. Patients with beta thalassemia trait often presents as mild microcytic hypochromic anemia with target cells. Their mean corpuscular volume is rarely >75 fL and the hematocrit is rarely . Ref: Wintrobe's Atlas of Clinical Hematology By Douglas. C. Tkachuk, Jan.V.Hirschmann, Page 14; Harrison's Principles of Internal Medicine, 18th Edition, Chapters 104-105; CURRENT Medical Diagnosis and Treatment, 2012, Chapter 13