Diagnosis and Management of Iron Deficiency Anemia

Laboratory Diagnosis

Low MCHC indicates hypochromic red cells, a hallmark of iron-deficient erythropoiesis where red blood cells contain insufficient hemoglobin 1
High TIBC reflects increased transferrin production by the liver attempting to capture any available iron, a compensatory mechanism in iron deficiency 2, 1
Low transferrin with high TIBC creates a low transferrin saturation (TSAT), calculated as (serum iron/TIBC) × 100, which will be <16-20% and confirms iron deficiency 1
Normal hemoglobin indicates this is early-stage iron deficiency before anemia has fully developed 3

Serum ferritin is the most specific test for iron deficiency: <15 μg/L is highly specific, <30 μg/L indicates depleted iron stores, and <45 μg/L warrants investigation even with inflammation 1
C-reactive protein (CRP) to identify inflammation that might falsely elevate ferritin 1
Complete blood count with MCV and RDW to assess for microcytosis that may not yet be apparent 1
Reticulocyte count to evaluate bone marrow response 1

Any level of iron deficiency should be investigated, even without anemia 3, 2
Gastrointestinal blood loss is the most common cause and requires endoscopic evaluation in men and postmenopausal women 3, 2
Menstrual blood loss is the most common cause in premenopausal women 3
Screen for celiac disease with tissue transglutaminase (tTG) antibody at presentation, as malabsorption from celiac disease is common in the UK and similar populations 3, 2

Oral iron is the initial treatment for most patients with iron deficiency, with expected response of 1-2 g/dL hemoglobin increase within one month, according to the American College of Physicians 1
Standard dosing: 200 mg elemental iron daily 5
IV iron is preferred when oral iron intolerance or non-adherence, malabsorption, heavy ongoing blood loss, or rapid iron repletion is needed, as recommended by the American Society of Nephrology 1

Hemoglobin and hematocrit should increase by 1-2 g/dL within one month 1
Serum ferritin should rise, indicating iron store repletion 1
Transferrin saturation should normalize to >20% 1
Reticulocyte hemoglobin content provides early indication of functional iron sufficiency 1