Red Blood Cell Assessment and Anemia

Anemia Definition

Abnormally low hemoglobin concentration in whole blood.

Erythrocyte Lifespan

Approximately 120 days.

Erythrocyte Composition

Primarily hemoglobin for oxygen delivery; carries about 70% of the body's iron.

Site of Hematopoiesis (Children vs Adults)

Children: marrow of all bones. Adults: flat bones (cranium, ribs, pelvis, vertebrae).

Hypoxia Response

Sensed by the kidneys, which respond by producing erythropoietin (EPO).

Erythropoietin (EPO)

A hormone secreted by the kidneys that enhances growth and differentiation of erythrocyte progenitors.

RBC Production Rate

Bone marrow produces about 2 million RBCs per second, amplifiable up to 10 times in hypoxia.

RBC Destruction Sites

Macrophages in the spleen, liver, and bone marrow digest old RBCs.

Reticulocytes

Premature enucleated RBCs containing ribosomes that spend 3 days in bone marrow and 1 day in blood before maturing.

Normal Reticulocyte Count

0.5% to 2.0% in circulating blood of healthy adults.

Requirements for Normal EPO Response

Responsive bone marrow, at least one healthy kidney, and adequate nutrition for HGB and DNA synthesis.

Signs and Symptoms of Anemia

Pallor (palms, nail beds, face, conjunctiva), dizziness, and fatigue.

Core Mechanisms of Anemia

1) Premature RBC destruction/acute blood loss, 2) Insufficient EPO stimulation, 3) Insufficient RBC production (nutritional).

RBC Concentration Reference Value

Average approximately 5 × 10⁶ cells/μL.

Hemoglobin Concentration Reference Value

Average approximately 15 g/dL.

Hematocrit (HCT) Reference Value

Average approximately 45%.

Rule of 3 in CBC

RBC (millions) × 3 ≈ HGB (gram %), and HGB × 3 ≈ HCT (volume %).

Mean Corpuscular Volume (MCV) Categories

Microcytic (

Mean Corpuscular Hemoglobin (MCH)

Quantity of hemoglobin in the average RBC; reference range is 26-32 pg.

Mean Corpuscular Hemoglobin Concentration (MCHC)

Concentration of hemoglobin in the average RBC (32-36 g/dL);

Corrected Reticulocyte Count (CR)

Adjusts reticulocyte count for decreased HCT; reference range is 0.5% - 2.5%.

Elevated Corrected Reticulocyte Count (>2.5%)

Indicates premature RBC destruction/loss or significant acute blood loss.

Normal or Low Corrected Reticulocyte Count

Indicates deficient RBC production (decreased EPO, bone marrow mass, or HGB/DNA synthesis).

Red Blood Cell Distribution Width (RDW)

Indicates variation in cell size (anisocytosis) and shape (poikilocytosis); reference range 11.5% - 14.5%.

Microcytic Anemia Mechanism

Caused by decreased hemoglobin synthesis, typically due to iron deficiency.

Macrocytic Anemia Mechanism

Caused by impaired DNA synthesis (Vitamin B12 or folate deficiency) resulting in megaloblastic precursors.

Pernicious Anemia

Macrocytic anemia caused by decreased Vitamin B12 absorption due to intrinsic factor loss.

Common Causes of Microcytic Anemia

Iron deficiency (chronic GI blood loss, dietary deficiency) and thalassemias.

Common Causes of Normocytic Anemia

Acute blood loss, hemolytic anemias (G6PD, sickle cell), and anemia of chronic disease.

Common Causes of Macrocytic Anemia

Vitamin B12 deficiency (malabsorption) and folate deficiency (inadequate diet, alcoholism).