Based on smear morphology and the red blood cell indices (mean cell volume [MCV], mean cell hemoglobin [MCH], mean corpuscular hemoglobin concentration [MCHC]), the patient has a severe microcytic, hypochromic anemia most likely caused by iron deficiency (see Chapter 5). This was confirmed by iron studies showing: Serum iron – I 0 Jlg/dl,TIBC – 460 Jlg/dl, % saturation – 2% Serum ferritin – 3 Jlg/L The history of repeated epistaxis and the positive test for blood in the stool strongly suggest chronic blood loss as the etiology of the iron deficiency. This obviously will require a careful workup of the gastrointestinal (GI) tract for a bleeding site and any correctable anatomic lesion. At the same time, a search for a coagulation defect is in order. Therefore, additional screening laboratory studies of importance include PT/international normal ized ratio (INR), aPTT, platelet function studies, and vWF antigen and activity (see Chapter 29). The following results were obtained in this patient PT/INR – 1 3.1 sec (< 1=”” 4.0=”” sec)/=”” 1.10=””>< 1=”” .30)=”” aptt=”” -=”” 28.9=””>