Laboratory evoluation
DR.EYAD ABOU ASALI
Diagnostic Tests
Functions of Blood
• Blood performs a number of functions
dealing with:
– Substance distribution
– Regulation of blood levels of particular
substances
– Body protection
Blood Functions:
Distribution
• Blood transports:
– Oxygen from the lungs and nutrients from the
digestive tract
– Metabolic wastes from cells to the lungs and
kidneys for elimination
– Hormones from endocrine glands to target
organs
Blood Functions:
Regulation
• Blood maintains:
– Appropriate body temperature by absorbing
and distributing heat to other parts of the body
– Normal pH in body tissues using buffer
systems
– Adequate fluid volume in the circulatory
system
Blood Functions:
Protection
• Blood prevents blood loss by:
– Activating plasma proteins and platelets
– Initiating clot formation when a vessel is broken
• Blood prevents infection by:
– Synthesizing and utilizing antibodies
– Activating complement proteins
– Activating WBCs to defend the body against foreign
invaders
Characteristics
Volume: A person has 4 to 6 liters of blood,
depending on his or her size. Of the total blood
volume in the human body, 38% to 48% is
composed of the various blood cells, also called
formed elements. The remaining 52% to 62% of the
blood volume is plasma, the liquid portion of blood.
Color: Arterial blood is bright red because it
contains high levels of oxygen. Venous blood has
given up much of its oxygen in tissues, and has a
darker, dull red color.
pH: The normal pH range of blood is 7.35 to 7.45,
which is slightly alkaline. Venous blood normally has
a lower pH than does arterial blood because of the
presence of more carbon dioxide.
Viscosity: Blood is about three to five times thicker
than water.
Plasma
Plasma is the liquid part of blood and is approximately
91% water. The solvent ability of water enables the
plasma to transport many types of substances: Nutrients
absorbed in the digestive tract, waste products of the
tissues; most of the carbon dioxide produced by cells is
carried in the plasma in the form of bicarbonate ions
(HCO3–).
• Plasma proteins: The clotting factors
prothrombin, fibrinogen, and others are
synthesized by the liver and circulate
until activated to form a clot in a ruptured
or damaged blood vessel. Albumin is the
most abundant plasma protein (synthesized
by the liver) and contributes to the colloid
osmotic pressure of blood. Alpha and beta
globulins are synthesized by the liver and
act as carriers for molecules such as fats.
Blood Cells
There are three kinds of blood cells: red blood cells,
white blood cells, and platelets. Blood cells are produced
from stem cells in hemopoietic tissue. After birth this is
primarily the red bone marrow, found in flat and irregular
bones such as the sternum, hip bone, and vertebrae.
Lymphocytes mature and divide in lymphatic tissue,
found in the spleen, lymph nodes, and thymus gland.
Red Blood Cells
Also called erythrocytes, red blood
cells (RBCs) are biconcave discs,
which means their centers are thinner
than their edges. Red blood cells are
the only human cells without nuclei.
Their nuclei disintegrate as the red
blood cells mature and are not needed
for normal functioning.
A normal RBC count ranges from 4.5
to 6.0 million cells per microliter. RBC
counts for men are often toward the
high end of this range; those for
women are often toward the low end.
Red blood cells (electron microscopes)
White Blood Cells
White blood cells (WBCs) are also called
leukocytes. There are five kinds of WBCs; all are
larger than RBCs and have nuclei when mature.
The nucleus may be in one piece or appear as
several lobes or segments.
A normal WBC count (part of a CBC) is 5,000 to
10,000 per microliter. This number is quite small
compared to a normal RBC count. Many of
WBCs are not circulating but are carrying out
their functions in tissue fluid or in lymphatic
tissue.
The granular leukocytes are the neutrophils,
eosinophils, and basophils. Neutrophils have light
blue granules, eosinophils have red granules,
and basophils have dark blue granules.
The agranular leukocytes are lymphocytes and
monocytes (macrophages), which have one piece
nuclei.
5 types of WBC
White Blood Cells
Monocyte in
tissue
Platelets
Platelets or thrombocytes are
not whole cells but rather
fragments or pieces of cells.
Some of the stem cells in the
red bone marrow differentiate
into large cells called
megakaryocytes, which break
up into small pieces that enter
circulation. These small, oval,
circulating pieces are platelets,
which may last for 5 to 9 days,
if not utilized before that.
Thrombopoietin is a hormone
produced by the liver that
increases the rate of platelet
production. A normal platelet
count (part of a CBC) is
150,000 to 300,000 microliter.
Thrombocytopenia is the term
for a low platelet count.
Activated platelets around an RBC
Platelets among RBCs
Platelets (Coagulation = Blood Clotting)
Platelets are necessary for hemostasis, which means prevention of blood loss.
There are three mechanisms, and platelets are involved in each:
o
Vascular spasm: when a large vessel such as an artery or vein is severed, the
smooth muscle in its wall contracts in response to the damage (called the
myogenic response). Platelets in the area of the rupture release serotonin,
which also brings about vasoconstriction. The smaller opening may then be
blocked by a blood clot.
o
Platelet plugs: when capillaries rupture, the damage is too slight to initiate
the formation of a blood clot. The rough surface, however, causes platelets to
change shape and become sticky. These platelets stick to the edges of the
break and to each other. The platelets form a mechanical barrier or wall to
close off the break in the capillary. Capillary ruptures are quite frequent, and
platelet plugs, although small, are all that is needed to seal them.
o
Chemical clotting: The stimulus for clotting is a rough surface within a vessel,
or a break in the vessel, which also creates a rough surface. Chemical clotting
begins in 15 to 120 seconds and has 3 stages:
RBC (Oxygenation)
Red blood cells contain the protein
hemoglobin (Hb), which gives them
the ability to carry oxygen. Each red
blood cell contains approximately 300
million hemoglobin molecules, each of
which can bond to four oxygen
molecules.
A determination of hemoglobin level is
also part of a CBC; the normal range
is 12 to 18 grams per 100 mL of
blood. There are four atoms of iron in
each molecule of hemoglobin. It is the
iron that actually bonds to the oxygen
and makes RBCs red. Hemoglobin
accounts for only about 10% of total
CO2 transport (most is carried in the
plasma as bicarbonate ions).
RBC (Blood Types)
Blood types are genetic. There are various red blood cell
factors or types including: the ABO group and the Rh
factor.
ABO Group: contains four blood types  A, B, AB, and
O. The letters A and B represent antigens (proteinoligosaccharides) on the red blood cell membrane. A
person with type A blood has the A antigen on the RBCs,
and someone with type B blood has the B antigen. Type
AB means that both A and B antigens are present, and
type O means that neither the A nor the B antigen is
present.
Circulating in the plasma of each person are natural
antibodies for those antigens not present on the RBCs.
Type A person has anti-B antibodies in the plasma; type
B person has anti-A antibodies; type AB person has
neither anti-A nor anti-B antibodies; and type O person
has both anti-A and anti-B antibodies.
ABO Typing (Genetics)
(A) The ABO blood
types. Schematic
representation of
antigens on the
RBCs and
antibodies in the
plasma.
(B) Typing and
cross-matching.
Rh Factor: is another antigen (often called
D) that may be present on RBCs. People
whose RBCs have the Rh antigen are Rh
positive; those without the antigen are Rh
negative. Rh-negative do not have natural
antibodies to Rh antigen (antigen is foreign).
If an Rh-negative person receives Rh-positive
blood by mistake, antibodies will be formed
just as they would be to bacteria or viruses.
O-
O+
A first mistaken transfusion often does not
cause problems, because antibody production
is slow upon the first exposure to Rh-positive
RBCs.
A-
A+
B-
B+
AB-
AB+
A second transfusion, however, when anti-Rh
antibodies are already present, will bring
about a transfusion reaction, with hemolysis
and possible kidney damage.
Acceptable transfusions are diagrammed and presuppose compatible Rh factors
Universal
donor
Universal
recipient
Transfusion typing and cross-matching
(empty boxes in the upper left half shows a mismatch)
Religious beliefs about blood transfusion
WBC (HLA – Tissue Typing)
The white blood cell types (analogous to RBC types
such as the ABO group) are called human leukocyte
antigens (HLA). The purpose of the HLA types is to
provide a “self” comparison for the immune system to
use when pathogens enter the body.
Tissue typing involves determining the HLA types of a
donated organ to see if one or several will match the
HLA types of the potential recipient. The chance of a
perfect HLA match is at 1 in 20,000.
HLA Molecule
HLA typing (matching) is used specifically in organ
transplant. If no match, the organ will be rejected by
the recipient (except corneal).
People with certain HLA types seem to be more likely
to develop certain non-infectious diseases. For
example, type 1 (insulin-dependent) diabetes mellitus
is often found in people with HLA DR3 or DR4.
HLA Concept
WBC (Immunity)
Neutrophils and monocytes are capable of the
phagocytosis of pathogens.
Neutrophils are the more abundant phagocytes,
but the Monocytes are the more efficient
phagocytes, because they differentiate into
macrophages, which also phagocytize dead or
damaged tissue at the site of any injury, helping to
make tissue repair possible.
Neutrophil
During an infection, neutrophils are produced more
rapidly, and the immature forms, called band cells,
may appear in greater numbers in peripheral
circulation.
Band cell
(neutrophil)
Monocyte
Eosinophils detoxify foreign proteins and
phagocytize anything labeled with antibodies.
This is especially important in allergic reactions
(asthma) and parasitic infections.
Basophils contain granules of heparin
(anticoagulant) and histamine (inflammation).
Lymphocytes: T cells help recognize foreign
antigens and may directly destroy some foreign
antigens. B cells become plasma cells that
produce antibodies to foreign antigens. Both T
cells and B cells provide memory for immunity.
Natural killer cells (NK cells) destroy foreign
cells by chemically rupturing their membranes.
Eosinophil
A high WBC count, called leukocytosis, is often
an indication of infection. Leukopenia is a low
WBC count, which may be present in the early
stages of diseases such as tuberculosis.
Basophil
What Do Blood Tests Show?
• Blood tests show whether the levels of different
substances in your blood fall within a normal range.
• Blood tests help doctors check for certain diseases and
conditions. They also help check the function of your
organs and show how well treatments are working.
Some of the most common blood tests
are a complete blood count (CBC), blood
chemistry tests, blood enzyme tests, and
blood tests to assess heart disease risk.
– A CBC can detect blood diseases and disorders.
– Blood chemistry tests measure different chemicals in
the blood. These tests give doctors information about
nerves, muscles (including the heart), bones, and
organs, such as the kidneys and liver.
– Blood enzyme tests measure the amounts of certain
enzymes in your blood. These tests can help
diagnose a heart attack.
– Blood tests to assess heart disease risk measure
substances in your blood that may show whether
you're at increased risk for coronary heart disease
• Many blood tests don't require any special preparation
and take only a few minutes. Other blood tests require
fasting (not eating any food) for 8 to 12 hours before the
test. You must let your patient know how to prepare for
blood tests.
• During a blood test, blood usually is drawn from a vein or
other part of the body using a needle. It also can be
drawn using a finger prick. Drawing blood usually takes
less than 3 minutes
• Blood tests alone can't be used to diagnose many
diseases or medical problems. However, blood tests can
help you and your patient learn more about his health.
Blood tests also can help find potential problems early,
when treatments or lifestyle changes may work best.
Complete Blood Count
CBC
Red cell count (RBC)
• signifies the number of red blood cells in a volume of
blood. Normal range is generally between 4.2 to 5.9
million cells/cmm. This can also be referred to as the
erythrocyte count and can be expressed in international
units as 4.2 to 5.9 x 1012 cells per liter.
low red blood cell count or low hemoglobin may
suggest anemia, which can have many causes. Possible
causes of high red blood cell count or hemoglobin
(erythrocytosis) may include bone marrow disease or low
blood oxygen levels (hypoxia).
Hemoglobin (Hb).
This is the amount of hemoglobin in a volume of
blood. Hemoglobin is the protein molecule within red
blood cells that carries oxygen and gives blood its red
color. Normal range for hemoglobin is different between
the sexes and is approximately 13 to 18 grams per
deciliter for men and 12 to 16 for women (international
units 8.1 to 11.2 millimoles/liter for men, 7.4 to 9.9 for
women).
Hematocrit (Hct).
This is the ratio of the volume of red cells to the volume
of whole blood. Normal range for hematocrit is different
between the sexes and is approximately 45% to 52% for
men and 37% to 48% for women. This is usually
measured by spinning down a sample of blood in a test
tube, which causes the red blood cells to pack at the
bottom of the tube.
Hemoglobin (varies with altitude)
• Male: 14 to 17 gm/dL
• Female: 12 to 15 gm/dL
Hematocrit (varies with altitude)
• Male: 41% to 50%
• Female: 36% to 44%
corpuscular volume (MCV) is
the average volume of a red blood cell. This is a
calculated value derived from the hematocrit and red cell
count. Normal range may fall between 80 to 100
femtoliters (a fraction of one millionth of a liter).
Mean Corpuscular Hemoglobin (MCH)
is the average amount of hemoglobin in the average
red cell. This is a calculated value derived from the
measurement of hemoglobin and the red cell count.
Normal range is 27 to 32 picograms
Mean Corpuscular Hemoglobin
Concentration (MCHC)
is the average concentration of hemoglobin in a given
volume of red cells. This is a calculated volume derived
from the hemoglobin measurement and the hematocrit.
Normal range is 32% to 36%.
Red Cell Distribution Width (RDW)
is a measurement of the variability of red cell size and
shape. Higher numbers indicate greater variation in size.
Normal range is 11 to 15.
Platelet count.
The number of platelets in a specified volume of blood. Platelets are
not complete cells, but actually fragments of cytoplasm (part of a cell
without its nucleus or the body of a cell) from a cell found in the
bone marrow called a megakaryocyte. Platelets play a vital role in
blood clotting. Normal range varies slightly between laboratories but
is in the range of 150,000 to 400,000/ cmm (150 to 400 x 109/liter).
A low platelet count (thrombocytopenia) may be the cause of
prolonged bleeding or other medical conditions. Conversely, a high
platelet count (thrombocytosis) may point toward a bone marrow
problem or severe inflammation.
White blood cell count (WBC)
is the number of white blood cells in a volume of
blood. Normal range varies slightly between laboratories
but is generally between 4,300 and 10,800 cells per
cubic millimeter (cmm). This can also be referred to as
the leukocyte count and can be expressed in
international units as 4.3 to 10.8 x 109 cells per liter.
White blood cell (WBC) differential count.
White blood count is comprised of several different
types that are differentiated, or distinguished, based on
their size and shape. The cells in a differential count are
granulocytes, lymphocytes, monocytes, eosinophils, and
basophils.
• a high WBC count (leukocytosis) may signify an
infection somewhere in the body or, less commonly, it
may signify an underlying malignancy. A low WBC count
(leukopenia) may point toward a bone marrow problem
or related to some medications, such as chemotherapy.
• A doctor may order the test to follow the WBC count in
order to monitor the response to a treatment for an
infection. The components in the differential of the WBC
count also have specific functions and if altered, they
may provide clues for particular conditions.
Blood Glucose
• This table shows the ranges for blood glucose levels
after 8 to 12 hours of fasting (not eating). It shows the
normal range and the abnormal ranges that are a sign of
prediabetes or diabetes.
* mg/dL = milligrams per deciliter.
† The test is repeated on another day to confirm the results.
Plasma Glucose Results
(mg/dL)*
99 and below
Diagnosis
normal
100 to 125
Prediabetes
126 and above
Diabetes†
Duke Bleeding Time
With the Duke method, the patient is pricked with a
special needle or lancet, preferably on the earlobe or
fingertip, after having been swabbed with alcohol. The
prick is about 3-4 mm deep. The patient then wipes the
blood every 30 seconds with a filter paper. The test
ceases when bleeding ceases. The usual time is about
1-3 minutes.
Ivy Bleeding Time
• The Ivy method is the traditional format for this test.
While both the Ivy and the Duke method require the use
of a sphygmomanometer, or blood pressure cuff, the Ivy
method is more invasive than the Duke method, utilizing
an incision on the ventral side of the forearm, whereas
the Duke method involves puncture with a lancet or
special needle. In the Ivy method, the blood pressure
cuff is placed on the upper arm and inflated to 40 mmHg.
A lancet or scalpel blade is used to make a shallow
incision that is 1 millimeter deep on the underside of the
forearm.
• A standard-sized incision is made around 10 mm long
and 1 mm deep. The time from when the incision is
made until all bleeding has stopped is measured and is
called the bleeding time. Every 30 seconds, filter paper
or a paper towel is used to draw off the blood.
• The test is finished when bleeding has stopped
completely.
• A normal value is less than 9 and half minutes.
• A prolonged bleeding time may be a result from
decreased number of thrombocytes or impaired blood
vessels. However, it should also be noted that the depth
of the puncture or incision may be the source of error.
Lee-White Clotting Time
• The Lee-White-test is one of the global tests which allow
the quantitative assessment of the coagulation system. It
is used to determine the coagulation time:
• A shortened Lee-White test is meaningless.
• A prolonged test indicates a defect of the intrinsic
system, or fibrinogen deficiency
• Absent coagulation is an indication for afibrinogenaemia
Prothrombin Time
• Prothrombin time (PT) is a blood test that measures how
long it takes blood to clot. A prothrombin time test can be
used to check for bleeding problems. PT is also used to
check whether medicine to prevent blood clots is
working.
• A PT test may also be called an INR test. INR
(international normalized ratio) stands for a way of
standardizing the results of prothrombin time tests, no
matter the testing method. So your doctor can
understand results in the same way even when they
come from different labs and different test methods.
Using the INR system, treatment with blood-thinning
medicine (anticoagulant therapy) will be the same. In
some labs, only the INR is reported and the PT is not
reported.
Why It Is Done
Prothrombin time (PT) is measured to:
• Find a cause for abnormal bleeding or bruising.
• Check to see if blood-thinning medicine, such as
warfarin (Coumadin), is working. If the test is done for
this purpose, a PT may be done every day at first. When
the correct dose of medicine is found, you will not need
so many tests.
• Check for low levels of blood clotting factors. The lack of
some clotting factors can cause bleeding disorders such
as hemophilia, which is passed in families (inherited).
• Check for a low level of vitamin K. Vitamin K is needed
to make prothrombin and other clotting factors.
• Check how well the liver is working. Prothrombin levels
are checked along with other liver tests, such as
aspartate aminotransferase and alanine
aminotransferase.
• Check to see if the body is using up its clotting factors so
quickly that the blood cannot clot and bleeding does not
stop. This may mean the person has disseminated
intravascular coagulation (DIC).
Activated Partial Thromboplastin Time
The activated partial thromboplastin time (APTT) test
is used after you take blood-thinners to see if the right
dose of medicine is being used. If the test is done for this
purpose, an APTT may be done every few hours. When
the correct dose of medicine is found, you will not need
so many tests.
Partial Thromboplastin Time
• Partial thromboplastin time (PTT) is a blood test that
measures the time it takes your blood to clot. A PTT test
can be used to check for bleeding problems.
• About 12 blood clotting factors are needed for blood to
clot (coagulation). The partial thromboplastin time is an
important test because the time it takes your blood to
clot may be affected by:
• Blood-thinning medicine, such as heparin. Another test,
the activated partial thromboplastin time (APTT) test, is a
better test to find out if the right dose of heparin is being
used.
• Low levels of blood clotting factors.
• A change in the activity of any of the clotting factors.
• The absence of any of the clotting factors.
• Other substances, called inhibitors, that affect the
clotting factors.
• An increase in the use of the clotting factors.
PTT with Mixing Test
• PTT is followed by mixing studies to check for possible
coagulation factor deficiencies or inhibitors. The patient’s
plasma is mixed with pooled normal plasma (a
combination of blood from different donors that has
normal amounts of all of the clotting factors). If the
patient has a factor deficiency, mixing their plasma with
pooled normal plasma should provide enough of the
missing factor(s) for the PTT to “correct” (clot within the
normal time frame). If it does correct, further coagulation
factor testing is done to determine those factors that are
deficient. If it does not correct, then the prolonged PTT
may be due to a specific or nonspecific inhibitor. Further
testing may then be done to check for antibodies to
specific factors and to identify nonspecific antibodies,
such as lupus anticoagulant and anticardiolipin
antibodies.
Clot Retraction Time
• The time required for a blood clot to separate from
the tube wall and express serum, usually completed
in 18 to 24 hours, but retarded or absent in persons
with thrombocytopenic purpura.
D-Dimer
D-Dimer test is a blood test used to rule out
active blood clot formation. If you have a
negative (normal) d-Dimer result, that nearly
rules out the possibility that you have a blood
clot actively forming. If you have an elevated
d-Dimer test result, that does not mean that
you have a blood clot; rather an elevated dDimer result means that additional testing
may be needed to see if a blood clot exists.
Lipoprotein Panel
The table below shows ranges for total cholesterol, LDL
("bad") cholesterol, and HDL ("good") cholesterol levels
after 9 to 12 hours of fasting. High blood cholesterol is a
risk factor for coronary heart disease
Total Cholesterol Level
Total Cholesterol Category
Less than 200 mg/dL
Desirable
200–239 mg/dL
Borderline high
240 mg/dL and above
High
Bilirubin, Direct
Serum
0.1-0.3 mg/dL
Bilirubin, Indirect
Serum
0.2-0.7 mg/dL
Bilirubin, total
Serum
0.3-1.0 mg/dL
Bleeding time
(Simplate)
Blood
<7 min
Iron
Serum or Plasma
6-26 mU/mL
Uric acid Men
Serum
2.5-8.0 mg/dL
Uric acid Women
Serum
1.5-6.0 mg/dL
Triglycerides
Serum
<160 mg/dL