This article will discuss the etiology, pathophysiology, signs and symptoms of anemia, and pertinent labs.
Introduction to Anemia
In general, anemia refers to having a decreased amount of hemoglobin or a lack of erythrocytes. There are many different types of anemia with many different etiologies. The etiologies of anemia can be separated into three main groups: hypoproliferative, maturation disorders, and hemorrhage.
Hypoproliferative is where the bone marrow cannot produce enough red blood cells. Some of the causes are bone marrow damage caused by chemotherapy, iron deficiency, certain chronic diseases and inflammation, and renal disease.
Maturation disorder is where red blood cells cannot mature properly, leading to maturation defects and empty red blood cells that cannot carry oxygen. Some of the causes are thalassemia, iron deficiency, folate deficiency, and vitamin B12 deficiency. There are two types of defects: cytoplasmic and nuclear maturation defects.
Hemorrhage is where there is significant blood loss, hemolysis, or autoimmune disease.
The USPSTF recommends that pregnant women are routinely screened for iron deficiency anemia and does not recommend routine screening in children 6-12 years old. The CDC recommends a low-dose iron supplement with at least 30 mg/day of iron.
Pathophysiology
Erythrocytes originated from pluripotent stem cells that went through GM-CSF, IL-3, cytokines, and EPO to become reticulocytes. EPO is secreted by the kidneys, which stimulates our body to produce red blood cells by detecting tissue erythrocyte concentration through oxygen content estimation. Reticulocytes reside in the bone marrow where they further mature into erythrocytes and enter the bloodstream where they function for 120 days.
Throughout this process, the nucleus of the cells becomes increasingly smaller as they mature until they have no nucleus as mature erythrocytes.
Signs and Symptoms of Anemia
The symptoms can be very broad. It can range anywhere from asymptomatic to rapid onset to chronic onset. It also depends on the type of anemia. For example, a B12 deficiency anemia can present with more neurologic issues.
Rapid onset symptoms include palpitations, angina, lightheadedness, and shortness of breath. Chronic onset symptoms include fatigue, weakness, headache, dyspnea on exertion, and sensitivity to cold.
Severe anemia symptoms that we need to watch out for are fainting, chest pain, angina, and heart attack.
When treating a patient, we need to consider the rate of development, age, and cardiovascular status. In addition, if the patient is rapidly declining, we should consider underlying causes such as RBC destruction, bone marrow suppression, iron deficiency, and medication history.
It is important to note that a decrease in hemoglobin in hospitalized patients can be normal. This is most likely due to an increased in fluids.
Laboratory Evaluation
There are two main categories when considering relevant lab values in the treatment of anemia. The first group is labs associated with blood. The second group is labs associated with essential nutrients that are important in the synthesis of blood.
Some of the labs that are relevant in the first group are:
- Complete Blood Count Panel. This includes hemoglobin, hematocrit, white blood cells, platelets, RBC distribution width, and erythrocyte indices.
- Erythrocyte indices include red blood cell, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCH)
- Hemoglobin: Males (14.0-17.5) and Females (12.3-15.3)
- Hematocrit: Males (40.7-50.3) and Females (36.1-44.3)
- Mean Corpuscular Volume (MCV) – macrocytic (>100), normocytic (80-100), and microcytic (<100).
- RBC distribution width measures the differences in the volume and size of red blood cells. This can be helpful in distinguishing mixed anemia and iron anemias. The higher the RDW number, the less accurate it is, which is why it should be used in conjunction with other lab values. The normal value for RDW is 11.5%-14.%.
- Reticulocyte index. Reticulocyte is a precursor to red blood cells. A low value may be reflective of low iron, B12, or renal insufficiency. A high value may be due to acute blood loss or hemolysis.
- Fecal occult blood test. This is a test to see if the patient is actively bleeding or not.
Some labs that are relevant in the second group are:
- Iron
- Serum Iron (iron bound to transferrin): M (45-160 mcg/dL) and F (30/160 mcg/dL)
- Serum Ferritin (storage iron in liver, spleen, and bone marrow): M (20-250 ng/mL) and F (10-150 ng/mL). It is important to note that chronic infection or inflammation can mask the values.
- Total Iron Binding Capacity (TIBC): 220-420 mcg/dL. This measures the capacity of transferrin binding to iron.
- Percentage Transferrin Saturation: 20-50%. This indicates how many iron-binding sites are occupied.
- Vitamin B-12
- Folate