Physiology Presentation

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Complete Blood Count (CBC)
It includes:
 White blood cell (WBC, leukocyte) count
 White blood cell types (WBC differential)
 Red blood cell (RBC) count
 Hematocrit (HCT, packed cell volume, PCV)
 Hemoglobin (Hgb)
 Red blood cell indices
Mean Corpuscular Volume
Mean Corpuscular Hemoglobin
Mean Corpuscular Hemoglobin
Concentration
 Platelet (thrombocyte) count
 Mean platelet volume (MPV)
 Red Blood Cell Distribution Width (RDW)
So what are Red Blood Cells Indices?
An index is a quantitative measurement of anything. Therefore
a Red Blood Cell Index would mean a quantitative
measurement of Red Blood Cells, the amount and the
concentration of Hemoglobin in them.
Red Blood Cell Indices include:
1. Mean Corpuscular Volume (MCV)
2. Mean Corpuscular Hemoglobin (MCH)
3. Mean Corpuscular Hemoglobin Concentration (MCHC)
They were first introduced by Wintrobe in 1929 to define the
size
(MCV) and hemoglobin content (MCH, MCHC) of red blood
cells.
 Red cell indices can be calculated if the values of
hemoglobin, hematocrit (packed cell volume), and red
blood cell count are known.
MEAN CORPUSCULAR VOLUME (MCV)
 It is the measure of average size or volume of RBCs.
 Expressed in femtoliters (fl; 10^-15 liter) or as cubic microns (μm ).
 Normal Value: 87± 7 fl (80-100 fl)
 Calculated by:
 Normal MCV—Normocyte
 High MCV—Macrocyte (Pernicious and megaloblastic anemia)
 Low MCV—Microcyte (Iron deficiency anemia)
MCV VALUES
AND DIFFERENT
TYPES OF
ANEMIA
MEAN CORPUSCULAR HEMOGLOBIN
(MCH)
MCH quantifies the amount or weight of hemoglobin per
RBC.
Measured in picograms (pg)
Normal Value: 29 ± 2 picograms (pg) per cell.
Calculated by:
MEAN CORPUSCULAR HEMOGLOBIN
CONCENTRATION (MCHC)
MCHC indicates the amount of hemoglobin per unit
volume.
In contrast to MCH, MCHC correlates the hemoglobin
content with the volume of the cell.
Expressed as g/dl of red blood cells or as a percentage
value.
Normal values: 34 ± 2 g/dl.
Calculated by
RBC Distribution Width (RDW)
o Coefficient of variation in size distribution of
RBCs
o Displayed as a percentage
o Normal value: 1 3 ± 1 .5%.
o Usual size of RBC is 6-8 µm
o Measured as : RDW = (Standard deviation of
MCV ÷ mean MCV) × 100
o Normal Value: Heterozygous Thalassemia (in
case of anemia)
o Increased Value: Anisocystosis (RBCs of unequal
sizes)
Practically Determining Blood Indices
Peripheral Blood Smear: A blood film or peripheral blood smear
is a thin layer of blood smeared on a microscope slide and then
stained in such a way to allow the various blood cells to be
examined microscopically.
 Examination of a blood film stained with Wright’s stain provides
information about various types of anemias.
 RBCs are 7-8 µm in diameter
 Peripheral concentration of Hb, central pallor.
 Used to determine type of anemia that is present in the patient.
 For instance, the occurrence of hypochromic, microcytic RBCs
indicates iron deficiency anemia, that may occur due to chronic
blood loss.
 The presence of macrocytes is often found in patients of
megaloblastic anemia due to deficiency of Vitamin B-12 and
Folic acid.
Automated Hematology Analyzers:
 A Beckman Coulter counter, using electrical analysis
based on Coulter’s principle, is used to perform CBC.
 In this process, a suspension of blood cells is passed
through a small orifice or aperture simultaneously with
an electrical current.
 This is known as the sensing zone.
 In this zone, each particle displaces its own volume of
electrolyte.
 The counter measures this volume change as a pulse,
with the height of each pulse being proportional to the
volume of the particle.
 From this Automated Analyzer, we get the values of
RBC indices, which can be interpreted for different
kinds of anemias:
ANEMIA
Anemia means deficiency of hemoglobin in the blood, which can be
caused by either too few red blood cells or too little hemoglobin in the
cells.
Types of Anemia
1. Morphologically Classified
2. Etiologically Classified
1. Normocytic Normochromic:
The MCV and MCHC values of RBCs are normal. But the number of
RBCs are less.
2. Macrocytic Hypochromic:
The MCV values are large. The MCHC values are low. Therefore the
RBCs appear to be of large size with pale coloration.
3. Macrocytic Normochromic:
The MCV values are again large. However, the MCHC values are
normal, so that the RBCs appear large with normal coloration.
4. Microcytic Hypochromic:
The MCV values are less. The MCHC values are also less. As a
consequence, the RBCs appear smaller with pale coloration
(central pallor is more than 50% of diameter; normally it is 3040%).
There are NO hyperchromic anemias. In spherocytosis, the
MCHC is increased due to loss of membrane and the consequent
spherical shape assumed by the cell.
Normocytic
Normochromic
Macrocytic
Normochromic
Microcytic
Hypochromic
Macrocytic
Hypochromic
But these were the characteristics of RBCS as they occur in different
types of anemias! What are the common types of anemias that show
these characteristics?
Why we need to assess Anemias based on red blood cell
indices?
Suppose a patient, after undergoing a CBC, comes to a clinician, with the
results of MCV, MCHC and MHC as under:
RBC index
Value
Normal Value
MCV
70 fl
80-100 fl
MCH
20 pg
27-31 pg
MCHC
28 g/dl
30-36 g/dl
We evaluate him as being Microcytic and Hypochromic.
Now we wish to identify the cause to administer proper treatment. This is
done by carefully planning the clinical causes and morphological
characteristics of anemias, as we will be doing next.
Type of Anemia
Hemorrhagic
Anemia
Hemolytic Anemia
(destruction of
RBCS)
Cause
Morphological
Characteristics of RBCS
Red Blood Cell Indices
Acute Blood Loss—after Normocytic,
accident
Normochromic
MCV, MCHC: within normal range
Chronic Blood Loss—
due to peptic ulcer,
hemophilia, prolonged
external and internal
bleeding
MCV and MCHC less than normal
Microcytic, Hypochromic
(due to iron deficiency)
Extrinsic (due to
external factors)
1. Liver Failure
2. Renal disorder
3. Hyperspleenism
4. Burns
Normocytic
5. Infections
Normochromic
(hepatitis, malaria)
6. Drugs (penicillin)
7. Lead Poisoning
MCV and MCHC values within normal range
Intrinsic (abnormal RBC
shape)
1. Sickle Cell Anemia Sickle Shape, normocytic MCV values are normal
2. Thalassemia
Microcytic, Hypochromic MCV and MCHC values are less
Nutrition
Deficiency Anemia
(due to deficiency
of substance
necessary for
erythropoiesis)
Iron Deficiency
Microcytic,
hypochromic
Macrocytic,
hypochromic
Macrocytic,
normochromic
MCV and MCHC less
MCV more, MCHC less
MCV more, MCHC less
MCV more, MCHC within normal range
Aplastic Anemia
Bone marrow aplasia
due to
i.
Radiation
ii. Toxic Chemicals
iii. Autoimmune
disorders ()
iv. Unknown cause
(idiopathic)
Normocytic,
normochromic
MCV and MCHC normal, RBC count less
Anemia of Chronic
Diseases
a.
Microcytic, normochromic Decreased MCV, MCHC normal
Vitamin B-12
(Pernicious Anemia)
Folic Acid
(Megaloblastic
anemia)
b.
c.
d.
Noninfectious
inflammatory
diseases—
rheumatoid
arthritis
Chronic infections
Chronic Renal
failure
Neoplastic
1. N Engl J Med
2005;352:1011-23
2. Guyton and Hall, Textbook
of Medical Physiology
3. Sembulingam, Essentials of
Medical Physiology
4. Walker et al, Clinical
Methods: The History ,
Physical, and Laboratory
Examinations.
5. Perkins S., Diagnosis of
Anemia
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