MLAB 1415- Hematology

Keri Brophy-Martinez

Anemia

Part One

Anemia

Anemia is the inability of the blood to supply the tissue with adequate oxygen for proper metabolic function.

Clinically, anemia is defined as a decrease in the normal concentration of hemoglobin or erythrocytes.

Anemia is not a disease, but an expression of an underlying disorder or disease.

Development of Anemia

Anemia occurs if: Erythrocyte loss or destruction exceeds the

maximum capacity of bone marrow erythrocyte production OR

Bone marrow erythrocyte production is impaired or abnormal

Causes of anemia

Acute blood loss (hemorrhage) Accelerated destruction of RBC’s (immune or

non-immune) Nutritional deficiency (iron, folate or B12) Bone marrow replacement (e.g. cancer) Infection Toxicity Hematopoietic stem cell arrest or damage Hereditary or acquired defect

Anemia Classifications Functional

Uses absolute and corrected retic count, RPI, and serum iron for classification Types

Survival Defects(Increased Destruction) Proliferation Defects(Decreased production) Maturation Defects

Anemia Classifications Morphologic

Uses erythrocyte indices (MCV) for classification Types

Macrocytic, Normochromic Causes: Folate or B12 deficiency, liver disease, alcoholism

Normocytic, Normochromic Causes: bone marrow failure, hemolytic anemia, chronic renal failure,

leukemia, metastatic malignancy Microcytic,Hypochromic

Most common anemia Causes: iron deficiency, sideroblastic anemia, thalassemia, chronic

diseases

Diagnosis of anemia

Clinical history Physical signs such as pallor, fatigue, weakness and

shortness of breath Laboratory tests

CBC Examination of the blood smear Reticulocyte - measures effective erythropoiesis Bone marrow examination Iron studies - iron, total iron-binding capacity (TIBC), ferritin Vitamin B12 and folate Erythropoietin level

Laboratory Tests for Measurement of Anemia

Lab Tests Hemoglobin Reference values

Male: 14-17.4 g/dl Female: 12-16 g/dl

Moderate anemia: 7-10 g/dl

Severe anemia: <7 g/dl

Hematocrit Reference values

Male: 42-52% Female: 36-46%

Parameters of the CBC (complete blood count)

Red Blood Count or RBC Hemoglobin Hematocrit

Note: the approximate relationship of the hemoglobin to the hematocrit is 1:3. This may vary with the cause of the anemia and the effect on the RBC indices, especially the MCV.

RBC indices MCV - mean cell volume

Normal:80-100 fL (femtoliters) Measured directly on automated cell counters Used to classify RBCs as normocytic, microcytic or macrocytic Indicates the average volume of the red cells

Calculation: Hct x 10

RBC

RBC Indices con’t

MCH - mean cell hemoglobin weight Normal: 28-34 pg A measurement of the hemoglobin content in RBC’s

Calculation: Hgb x 10

RBC

MCHC - mean cell hemoglobin concentration Normal: 32-36 % Used to classify RBCs as normochromic, or hypochromic A measure of the concentration of hemoglobin in the average RBC

Calculation: Hgb x 100

Hct

Parameters of the CBC(complete blood count)

RDW -Red Cell Distribution Width Calculated index used to identify anisocytosis Normal: 11.5-14.5%

Calculation: Standard deviation of MCV x100

Mean MCV

Reticulocyte

Adult reference range: 0.5 - 2.5% Useful in determining the response to the anemia and the

potential of the bone marrow to manufacture RBC’s. Expressed as a percentage of the RBC’s.

When anemia is present, it is helpful to correct the retic using the patient’s hematocrit in order to assess appropriate bone marrow response

A supravital stain called New Methylene Blue is used to stain reticulocytes. On a Wright’s stained smear, reticulocytes appear as bluish red cells. The term used for retics on Wright’s stain is polychromasia.

Corrected retic% = retic % X Patient hct Normal hct* based on age and sex

[*Normal female hct = 42%][*Normal male hct = 45%]

Reticulocyte

Prematurely released retics remain in the blood and take from ½ to 1 ½ days longer to mature. This will cause even the “corrected” retic to be elevated, so a calculation must be performed to correct for this situation to obtain the reticulocyte production index (RPI). A maturation time table is used for this calculation.

Indicator of the adequacy of the bone marrow response in anemia RPI>2: good bone marrow response RPI<2: inadequate response

RPI = corrected retic

maturation time in days

Adult Reference Ranges

Red Blood Cells Male: 4.5-5.5 x 106 /µlFemale: 4.0-5.0 x 106 /µl

Hemoglobin Male: 14-17.4 g/dlFemale: 12-16 g/dl

Hematocrit Male: 42-52%Female: 36-46%

MCV 80-100 fL

MCH 28-34 pg

MCHC 32-36 %

Reticulocyte 0.5-2.5%

RDW 11.5-14.5%

References

Harmening, D. M. (2009). Clinical Hematology and Fundamentals of Hemostasis. Philadelphia: F.A Davis.

McKenzie, S. B., & Williams, J. L. (2010). Clinical Laboratory Hematology . Upper Saddle River: Pearson Education, Inc.