Module 1: An Introduction to the Anemias Flashcards
anemia
reduced Hb below normal reference range
Below 140g/L in Males
below 120g/L in Females
most anemias are accompanied by
low hematocrit and/or RBC count
Polycythemia
RBC count (and usually also hematocrit) are increased above ref range
2 types of anemias
absolute and relative
Absolute anemia
hb concentration is decreased due to
- decreased absolute # of RBC in blood
- Decreased Hb inside the RBC
Absolute anemia results in
decrease in oxygen carrying capacity of blood due ti decrease in red cell mass
Mild to severe hypoxia
Symptoms of absolute anemia
pallor of mucous membranes shortness of breath on mild excertion weakness lethargy palpitations headaches
2, 3 BPG in relation to most anemias
level of 2, 3 BPG in red cells in increased
Oxygen dissociation curve is shifted to the right
Oxygen is release more easily and completely to hypoxic tissue
Relative anemia
Hb concentration decreased by increasing plasma volume (by dilution)
No decrease in Red cell mass or any loss of oxygen carrying capacity
Often seen in third trimester pregnancy
Only sure way of differentiating absolute from relative
measure red cell volume (RCV) and/or plasma volume (PV) using radioisotope techniques
3 causes of absolute anemias
Decreased or Ineffective erythropoiesis (RBC production is decrease; decreased # of cells survive)
Increased Hemolysis (increased destruction or decreased survival of RBC in circulation)
Blood loss
relation between rate of production and hemolysis/loss
Rate of production IS LESS THAN rate of hemolysis/loss
Most useful classification of anemia is
morphologic/etiologic classification
based on red cell indices and rbc morphology
4 types of absolute anemia
Hypochromic
Macrocytic
Normochromic Normocytic
Hemolytic
Hypochromic anemia lab results
Red cell indices are decreased (MCV, MCH, MCHC)
Red cell morphology: Hypochromic and often microcytic
Macrocytic anemia lab results
Red cell indices are variable (MCV increase, MCH variable, MCHC normal)
Red cell morphology: Macrocytic
Normochromic normocytic anemia lab results
Red cell indices are normal
Red cell morphology: normal
Hemolytic anemia lab results
Red cell indices are often normal
Red cell mophology: poikilocytosis (abnormal variation in shape)
3 questions to answer for physician
Is an anemia present?
If yes, what kind is it?
What is its cause?
Hemoglobin is based on
colorimetric measurement manually or by automated instrumentation
Hematocrit (pcv) is based on
centrifugation of blood or calculated on an automated instrument
RBC indices
Mean Cell Volume (MCV) indicates size
Mean Cell Hb (MCH) indicates Hb mass
Mean cell Hb concentration (MCHC) in an average RBC
RBC distribution width (RDW) which is an index of size variation which indicates amount of anisocytosis (variation in size) present
Mean Cell volume (MCV)
indicates volume in femtoliters (fL; x10^-15) of an average red cell in a blood sample
From histogram or can be calculated
MCV=Hct/RBC
Normal range 80-100fL
Normal MCV indicated
RBC of normal size present (normocytes present)
Increased MCV indicates
at least some cells with increase volume
Due to greatly increased # of young cells polychromatophilic erythrocytes (reticulocytes) or enlarged mature cells (macrocytes)
Decreased MCV indicates
smaller than normal erythrocytes (microcytes) present
Mean Cell Hemoglobin (MCH)
indicates weight of Hb inside an average RBC in picograms (pg; x10^-12)
MCH = Hb/RBC
Normal range is 27-32pg
Mean Cell Hemoglobin Concentration (MCHC)
indicates the Hb concentration inside the RBC expressed as grams of Hb per L of RBC (g/L)
MCHC = Hb/Hct
Normal range is 320-360g/L
Normal MCHC indicates
normal concentration of Hb within the RBC
Normochromic
Decreased MCHC indicates
presence of red cells lacking normal amounts of Hb in blood
Hypochromia
Increased MHCH
Typically erroneous because volume of RBC usually increased to accommodate greater amounts of Hb (thus MCH may be increased but MCHC remains normals due to increased volume of the cell; Term hyperchromia is NOT used)
MCHC May be truly increased: Spherocytes present in blood (used term spherocytosis NOT hyperchromia), Lipemia or cold agglutinins (considered an interference)
Red cell distribution width (RDW)
indicates the amount of RBC volume/size variation (anisocytosis) in a sample
Obtained by calculating coefficient of variation (CV) of red cell volumes from red cell volume histogram (Expressed as %)
Normal range is 11.5-14.5%
Lab results:
RDW normal
MCV increased
Interpretation:
No anisocytosis present
All macrocytes
Lab results:
RDW increased
MCV increased
Interpretation:
Anisocytosis present
Macrocytes and normocytes, or macrocytes, normocytes and microcytes
Lab results:
RDW Normal
MCV Normal
Interpretation:
No Anisocytosis present
Normal cells
Lab results:
RDW Increased
MCV Normal
Interpretation:
Anisocytosis present
Equal amounts of microcytes and macrocytes (average out to be normal)
Lab results:
RDW increased
MCV decreased
Interpretation:
Anisocytosis present
Microcytes and normocytes, or microcytes, normocytes and macrocytes
Lab results:
RDW normal
MCV decreased
Interpretation:
No Anisocytosis present
All microcytes
MCV, MCH and MCHC act as quality control check on
RBC count, hematocrit, and Hb results
RDW allows easier interpretation of the
MCV
