Red Blood Cell anomalies (1) Flashcards
Increased number of red cells with variation in size
Anisocytosis
Size of normal RBCs (normocytes)
6-8 um in diameter
Normal MCV value
80-100 fL
Larger than normal RBCs (>8.0 um), MCV > 100 fL, impaired DNA synthesis
Macrocytes
Smaller than normal RBCs (diameter < 6.0 um), seen when MCV is < 80 fL, defective hemoglobin formation
Microcytes
Four ways to detect anisocytosis
1) Using the nucleus of a small lymphocyte in a peripheral blood smear (PBS), 2) Using the MCV value, 3) Using the RBC histogram, 4) Using the RDW value
Average volume of individual RBCs
MCV
Visual display of cell size (X-axis) and cell frequency (Y-axis), provided by high-volume instruments
RBC histogram
Two parameters calculated from RBC histogram
MCV and RDW
RBC histogram range for RBCs
36 fL to 360 fL
MCV formula
MCV = HCT * 10 / RBC count
Decreased MCV value
Microcytic < 80 fL, RDW > 14.5%
Normocytic MCV
80-100 fL, RDW 11.5 - 14.5%
Macrocytic MCV
> 100 fL, RDW > 14.5%
RDW in macrocytic and microcytic
Increased regardless of size
RBC histogram measurement range
Can measure cells as small as 24 fL
Effect of elevated leukocyte count on RBC histogram
Affects the RBC histogram
Shift to the right in RBC histogram indicates
macrocytic RBCs
Shift to the left in RBC histogram
Indicates microcytic RBCs
Bimodal RBC histogram curve
Indicates two populations of RBCs, such as in blood transfusion, cold agglutinin disease, or hemolytic anemia with schistocytes
Wider or flattened RBC histogram curve
Indicates more variation in cell size, the population is not homogeneous
Methods to calculate RDW
RDW-CV (coefficient of variation), RDW-SD (standard deviation)
RDW-CV based on
Width of the RBC distribution curve and mean RBC size
RDW-SD based on
Measurement of the width of the RBC distribution curve at 20% above the baseline
RDW-CV reference range
11.5 - 14.5%
RDW-SD reference range
39 - 46 fL
RDW-CV measurement method
Depends on the width of the distribution curve and MCV
RDW-SD advantage
Not influenced by MCV, better measure of erythrocyte variability, especially in abnormal conditions
Methods to evaluate RBC size
PBS, MCV, RBC Histogram
Methods to detect anisocytosis
RDW, PBS, MCV, RBC Histogram
Reference range for RDW in newborns
14.2 to 19.9%
RDW in newborns
Markedly increased, decreases to adult levels by 6 months of age
Abnormal RDW indication
Wider-than-normal RBC histogram
Anemia type
Normal, little or no anisocytosis, Decreased MCV (microcytic)
Anemia of chronic inflammation (ACI)
Normal, little or no anisocytosis, Normal MCV (normocytic)
G6PD deficiency
Increased MCV (macrocytic), Normal, little or no anisocytosis
Liver disease
Anemia
Increased anisocytosis, Decreased MCV
Iron deficiency anemia (IDA)
Anemia
Increased anisocytosis, Normal MCV
Sickle cell anemia
Anemia
Increased anisocytosis, Increased MCV
Megaloblastic anemia
Variation in normal coloration of RBCs, may involve hypochromic and normochromic cells in the same smear
Anisochromia
Normal RBC coloration
Central pallor is approximately 1/3 the diameter
Conditions associated with Anisochromia
Sideroblastic anemias, hypochromic anemia after transfusion or iron therapy
Hypochromic cells appearance
Central pallor >1/3 of diameter, usually microcytic
Grading of hypochromia 1+
Area of central pallor = 1/2 diameter
Grading of hypochromia 2+
Area of central pallor = 2/3 diameter
Grading of hypochromia 3+
Area of central pallor = 3/4 of diameter
Grading of hypochromia 4+
Thin rim of hemoglobin
A.k.a. Pessary cell, Ghost cell; RBC with a thin rim of hemoglobin and a large, clear center; observed in iron deficiency anemia
Anulocyte
Hyperchromic cells appearance
RBCs that lack central pallor, caused by shape change (e.g., spherocytes); true hyperchromia occurs when MCHC is high
Only disease where MCHC is high above reference range
Hereditary Spherocytosis
Key clinical manifestations of symptomatic HS
Splenomegaly, Anemia, Jaundice
DAT (direct antiglobulin test) in HS
Negative
MCV in HS
Normal to low
MCH in HS
Normal
MCHC in HS
Slightly increased
Immune disorders with spherocytes
Usually characterized by a positive DAT result
Autohemolysis test in HS
Greatly increased (can be corrected with glucose or ATP)
OFT (Osmotic Fragility Test) in HS
Increased osmotic fragility, not diagnostic of HS
EMA binding test in HS
Decreased fluorescence (flow cytometry)
Polychromatophilic erythrocytes
Larger than normal red cells with bluish tinge caused by residual RNA (Wright’s stain)
Polychromasias are associated with
Decreased RBC survival, hemorrhage, erythroid hyperplastic marrow
Grading of Polychromasia - Slight
1% of Polychromatophilic RBCs
Grading of Polychromasia - 1+
3% of Polychromatophilic RBCs
Grading of Polychromasia - 2+
5% of Polychromatophilic RBCs
Grading of Polychromasia - 3+
10% of Polychromatophilic RBCs
Grading of Polychromasia - 4+
> 11% of Polychromatophilic RBCs