2. Learning Targets
• Identify common blood tests and their
purpose in diagnostics.
• Discuss lab skills, safety, and procedure.
3. Blood as a Diagnostic Tool
• Blood is often used as a diagnostic for several
reasons:
– Blood is easily accessible. It is relatively harmless
to obtain and low risk. It is also not expensive to
test blood.
– Blood can give us lots of information. It contains
cells and plasma, and gives a good general status
of the body function.
4. Limitations of Blood Tests
• Cannot be treated as absolutes in most cases,
due to margin of error.
– When we test blood we take only a small sample,
which should be representative, but is not always.
– Lurking variables can skew results.
– Issues in the central nervous system are hard to
see with blood tests due to blood brain barrier.
5. Lab Safety Basics
• Remember Standard Precautions
– Just because the patient is not standing their, you
should still observe all appropriate precautions with
body fluids.
• Be especially careful with transferring blood and
obtaining specimens.
– Higher risk for contamination.
• Sharps are common.
– Lots of needles are used and disposed in the lab
setting. Do it correctly.
6. Lab Skills
• Venipuncture – obtaining blood via a peripheral stick.
– This is adequate for most lab requests.
– Involves locating, accessing, and then de-accessing a vessel near
the peripheral surfaces of the skin.
• Arterial Puncture – obtaining blood from an artery.
– This is higher risk due to pressurized blood in these vessels.
– After care is especially important. Lack of appropriate care can
lead to bleeding or hematoma.
• Obtaining Blood from a Central Line
– This is a special skill, usually only performed by an RN.
– Proper technique and precautions use to high risk of infection.
7. What are those colored tubes about?
• They are called “Vacutainers”
– Test tubes used in the tests are voided of air, and therefor will
pull a specimen in, only until the appropriate amount is present.
• The color to indicates what type of additive is in the tube.
– Some tubes have enzymes that prevent clotting, cause
separation of blood parts, etc.
– This is needed depending on the different test to be run.
• Draw order:
– It does matter what order tubes are drawn in.
– Some tests need to be drain first, others should have blood
wasted (or used in other tests) before hand.
8.
9. Blood Components
• When we test blood, we have several factors to
look at:
– Plasma, which contains lots of solutes (hormones,
nutrient levels, sugar, waste products, electrolytes,
chemical factors etc.)
– Red Blood Cells (which we can count, test for reaction
properties, shape, etc.)
– Platelets (tell us about blood clotting)
– White blood cells (there are many types, and different
levels of each can indicate disease or infection)
12. A Closer Look at Blood Components
Red Blood Cells
• We can look at the
shape/size of the cells, the
number of cells or even
specific chemical factors
about the cells to give us
information about the body.
• The normal range for RBC is:
4.2 to 6.1 million per
microliter.
Hemoglobin
• This usually corresponds to
RBC, but is specifically is the
oxygen carrying molecules
in the cell.
• Normal range: 12-18 grams
per deciliter.
• In both of these, men tend
to run higher than women.
13. A Closer Look at Blood Components
Albumin
• Albumin is the prime
protein in blood, and
creates the appropriate
level of osmotic pressure to
prevent loss of excess blood
into the tissues.
• Low levels can indicate liver
disease or starvation.
Platelets
• Platelets are a key part of
the clotting cascade. They
are cell fragments made
from special bone marrow
cells.
• These cells must work
together with the various
clotting factors to stop
bleeding when it occurs.
14. White Blood Cells
Elevated Total WBCs
• This is a count of all white
blood cells (5 types).
Further more specific
counts may be used to
figure out specific
problems.
• Increased levels indicate
stress, or infection.
Decreased levels indicate
immune suppression.
Elevated Individual Types of
WBCs
• Certain types of WBCs
respond to different needs
in the body.
– Elevated Eosinophils may
indicate a parasite infection
or allergic reaction.
– Immature white blood cells
indicate a serious systemic
infection called sepsis.
– Decreased levels of Killer T
Cells indicates advancing HIV
15. Common Blood Tests: The Blood Count
(CBC)
• A complete blood count (CBC) is a blood test used to evaluate your
overall health and detect a wide range of disorders, including
anemia, infection and leukemia.
• A complete blood count test measures several components and
features of your blood, including:
– Red blood cells, which carry oxygen
– White blood cells, which fight infection
– Hemoglobin, the oxygen-carrying protein in red blood cells
– Hematocrit, the proportion of red blood cells to the fluid component,
or plasma, in your blood
– Platelets, which help with blood clotting
• Abnormal increases or decreases in cell counts as revealed in a
complete blood count may indicate that you have an underlying
medical condition that calls for further evaluation.
16. Common Blood Tests: BMP and CMP
CMP – gives basic blood chem, plus information
about liver and kidney function.
• Albumin – blood protein
• Alkaline Phosphatase – liver test
• ALT - liver test
• AST - liver test
• BUN – kidney function indicator
• Creatinine – kidney function test
• Calcium
• Chloride
• Carbon Dioxide
• Glucose
• Potassium
• Sodium
• Serum Bilirubin
• Total Protein
BMP – gives a basic picture of blood
chem, plus kidney function.
• BUN – Blood Urea Nitrogen
• Creatinine
• CO2
• Glucose
• Chloride
• Potassium
• Sodium
17. Common Blood Tests: ANA and ESR
ESR – Erythrocyte Sedimentation
Rate
• Literally measures o how
fast the RBCs sink to the
bottom of the tube.
• Faster Rates occur in
diseases that result in
systemic inflammation
(autoimmunity issues
especially)
ANA – Antinuclear Antibody
• This test measures the
presence of antibodies in
the blood that are targeted
at the body’s own tissues.
• These rates are elevated in
autoimmune issues, liver
disease and inflammatory
issues.
18. Common Blood Tests: Coomb’s Test
• This test measures antibodies that are in the
blood (indirect) or are bound to the red blood
cells (direct).
– Elevated levels may occur in reactions to
transfusion, infectious disease, autoimmune
disease.
19. Common Blood Tests: Liver Function
Tests
• Measures of several blood components can give
indication to liver function:
– ALP
– AST/ALT
– Bilirubin
• These markers and enzymes indicate either
directly or indirectly damage to the liver.
• Liver disease may also result in elevated
inflammation markers, low blood counts or blood
protein.
20. Common Blood Tests: Kidney Function
• Tests that monitor the function of the kidneys
mainly rely on measuring levels of waste
product in the blood. As levels rise, it
indicated the kidneys are not working.
– BUN
– Creatinine
• Other indicators of kidney issues can be found
in urine, or be expressed as electrolyte
imbalance or anemia.
21. Common Blood Tests: Blood Culture
• If a septic infection is suspected (an infection
which is spreading in the blood), blood
cultures can be performed.
– Just like cultures of wounds or other fluids, blood
is obtained and allowed to “grow out” on a
medium.
– Then, any growth is tested as to what it is and
what medication is effective.
22.
23. Common Blood Tests: Blood Clotting
Studies
• Other than the number of platelets present,
several other measures can be made concerning
how long it takes the blood to clot. This can be
used to identify a problem or to see if medication
meant to slow clotting is effective.
– INR: international normalized ratio is a measure of
how long it takes certain factors to begin working in
the clotting cascade. It is used to monitor medication
levels.
– PT/PTT – measures how long it takes for Prothrombin
and thrombin to activate in the clotting cascade.
