Anemia Diagnosis and Classification

Initial Assessment and Classification

The American Gastroenterological Association recommends a complete blood count (CBC) as the first test for patients with suspected anemia, with hemoglobin levels defining anemia as <12 g/dL for women and <13 g/dL for men 1, 2
Red Blood Cell Indices, particularly Mean Corpuscular Volume (MCV) and Red Cell Distribution Width (RDW), are essential for initial classification of anemia 3, 4
Reticulocyte Count helps distinguish between production defects and increased destruction/loss of red blood cells 3, 5
The World Health Organization defines anemia as a hemoglobin level <12 g/dL for women and <13 g/dL for men, with MCV <80 fL indicating microcytic anemia, 80-100 fL indicating normocytic anemia, and >100 fL indicating macrocytic anemia 1, 2

Iron Deficiency Anemia (IDA) is characterized by low serum ferritin (<30 μg/L in non-inflammatory states), low transferrin saturation, and elevated RDW 3, 2, 6
Thalassemia is characterized by normal or elevated ferritin, and requires hemoglobin electrophoresis for confirmation 3, 6
Anemia of Chronic Disease (ACD) is characterized by elevated serum ferritin (>100 μg/L), low transferrin saturation (<20%), and normal or low MCV and MCH 7, 3
Mixed Deficiency Anemia may have normal MCV due to counterbalancing effects of different deficiencies, and high RDW indicates coexisting deficiencies 7, 3, 6

Reticulocyte Response Analysis indicates production defect (deficiencies, bone marrow failure) with low/normal reticulocytes, and hemolysis or blood loss with elevated reticulocytes 3, 6
Iron Studies Interpretation shows serum ferritin as the most sensitive marker for iron stores, with <30 μg/L indicating iron deficiency without inflammation, and 30-100 μg/L with inflammation indicating possible iron deficiency 5, 2, 7
Transferrin Saturation represents iron available for erythropoiesis, with <20% indicating functional or absolute iron deficiency 5, 7

Inflammatory Conditions alter interpretation of iron studies, and CRP should be measured to assess inflammation 3
Soluble transferrin receptor levels may help distinguish IDA from ACD 3
The European Crohn’s and Colitis Organisation recommends considering underlying causes of deficiencies, such as GI bleeding in iron deficiency 5

Relying solely on MCV for classification may lead to misdiagnosis, as coexisting conditions may neutralize MCV changes 3, 6
Misinterpreting ferritin without considering inflammatory status may lead to incorrect diagnosis 2
Failing to consider hemolysis when reticulocyte count is elevated may lead to delayed diagnosis 3
Not investigating underlying causes of deficiencies may lead to inadequate treatment 5