Hematology Studies
Test: Total Hemoglobin (Hgb or Hb)
A test used to determine the amount of hemoglobin in the blood. Hgb
is the pigment part of the erythrocyte, and the oxygen-carrying part of
the blood.
Normal Values:
males: 12-17 grams/100ml
females: 11-15 grams/100ml
Clinical Implications:
A Low hemoglobin level indicates anemia. Estimates of Hgb in each
RBC are moderately important when determining the total blood Hgb.
However, hemoglobin findings are even more dependent upon the total
number of RBC's. In other words, for the diagnosis of anemia, the
number of RBC's is as important as the hemoglobin level.
Blood hemoglobin level has become a "routine" lab test for most
patients admitted to hospitals today. Hgb is obviously important for the
diagnosis of anemia and hemorrhage. It is equally important for
diagnosing many lesser known diseases.
The test can be performed upon capillary blood, such as drawn from
the finger stick. The test is often performed along with other tests,
thereby requiring a larger specimen of blood, as from venipuncture.
Hemoglobin in the body is dependent upon amounts of iron. A lack of
available iron causes one type of anemia, due to the reduced production
of hemoglobin. Remember that in the strictest sense, anemia is not in
itself a diagnosis, but rather a symptom that there is something else
wrong in the body. For example, malnutrition (low iron levels), would
be the diagnosis of the patient, not just the anemia. The secondary
diagnosis would be anemia, but malnutrition must be treated in order to
"cure" the anemia.
*Note--Fetal Hemoglobin:
Fetal Hb (Hb F), is a normal Hb product in the red blood cells of a
fetus and in smaller amounts in infants. It constitutes 50% to 90% of
Hb in a
newborn; the remaining Hb consists of Hb A1 and Hb A2 the Hb in adults.
Under normal conditions, the body ceases to manufacture fetal Hb
sometime during the first year of life, and from that point on
manufactures adult Hb. If this changeover does not occur and fetal Hb
continues to constitute more than 5% of the Hb after age six months, an
abnormality should be suspected, particularly thalassemia.
VARIATIONS OF HEMOGLOBIN TYPE AND DISTRIBUTION (in adults)
| Percentage of total Hemoglobin |
hemoglobin |
Clinical Implications |
|
| Hb A |
95% to 100% |
Normal |
| Hb A2 |
4% to 5.8% |
b-thalassemia minor |
| |
1.5% to 3% |
b-thalassemia major |
| |
Under 1.5% |
b-d-thalassemia minor |
| Hb F |
Under 2% |
Normal |
| |
2% to 5% |
b-thalassemia minor |
| |
10% to 90% |
b-thalassemia major |
| |
5% to 15% |
b-d-thalassemia minor |
| |
5% to 35% |
Heterozygous hereditary Persistence of fetal Hb (HPFH) |
| |
100% |
Homozygous HPFH |
| |
15% |
Homozygous Hb S |
| Homozygous Hb S |
70% to 98% |
Sickle Cell disease |
| Homozygous Hb C |
90% to 98% |
Hb C disease |
| Heterozygous Hb C |
24% to 44% |
Hb C trait |
Test: Hemoglobin Electrophoresis
Hemoglobin electrophoresis is probably the most useful laboratory
method for separating and measuring normal and some abnormal Hb.
Through electrophoresis, different types of Hb are separated to form a
series of distinctly pigmented bands in a medium (cellulose acetate or
starch gel). Results are then compared with those of a normal sample.
Hb A (same as Hb A1), Hb A2, Hb S, Hb C, and Hb F are routinely
checked, but the laboratory may change the medium or its pH to expand
the range of the test. This test, by measuring the different types of
Hb, is used to detect normal and abnormal types of hemoglobin, to aid in
the diagnosis of thalassemia, and to aid in the diagnosis of sickle
cell disease or trait.
**For normal or reference values, see the chart above.
Test: Hematocrit Hct
The hematocrit measures percentage by volume of packed red blood
cells in a whole blood sample. For example, a HCT of 40% indicates that
a 100-ml sample of blood contains 40 ml of blood cells. Packing is
achieved by centrifuging anticoagulated whole blood in a capillary tube
so that the cells are tightly packed without hemolysis.
Normal Values:
males: 40 to 50 percent
females: 37 to 47 percent
Clinical Implications:
Two small specimens of blood are obtained and compared. They are the
same amount of blood exactly. One specimen is then centrifuged and
subsequently compared to the first specimen. A percentage is then
obtained from that comparison. This comparison is the hematocrit, Hct.
The value of the hematocrit is dependent upon the number of RBC's. If
the Hct is abnormal, then the RBC count is possibly abnormal. If the
RBC count turns out to be normal, then the average size of the RBC is
probably too small. Shock, hemorrhage, dehydration, or excessive IV
fluid administration can reduce the Hct.
As you can see, there are many factors which can influence the
results of the hematocrit test. However, this is still a good baseline
lab test for the patient. It helps the physician to diagnose and to
treat the patient with any disease which will lower or raise the Hct
levels.
Test: Red Blood Cell Count RBC count
A count of actual (or estimated) number of RBC's per cubic mm of whole blood.
Normal Values:
males: 4.5 to 6.0 million/cu mm blood
females: 4.0 to 5.5 million/cu mm blood
Clinical Implications:
The RBC count is useful for determining such problems as anemia and
hemorrhage. In combination with other hematology tests, it can be quite
useful for diagnosis. This test can also give an indirect estimate of
the hemoglobin levels in the blood. RBC's are actually "Red Blood
Corpuscles," (non-nucleated cells). The term corpuscle indicates that
it is a mature Red Blood Cell. Once the immature cell has matured, it
is then, and only then, capable of carrying oxygen. It is then also not
"technically" a cell anymore. Once it has matured, it loses its nucleus
and can no longer be properly termed a cell. It would be called a
corpuscle. However, everyone still refers to them as RBC's (cells).
The source of the specimen is whole blood, capillary, or venous blood.
Test: Red Cell Indices (Wintrobe Indices)
A report of the individual characteristics of the RBC. The following
are those characteristics which are used to indicate anemia. If
abnormal findings are present, the anemias can be defined as macrocytic,
microcytic, hypochromic, others. When this is discovered, the exact
cause of the anemia can be determined more easily.
The following are all part of indices:
- MCV
- MCH
- MCHC
1. MCV - Mean Corpuscular Volume
The volume of the average RBC
calculated by:
Hct x 10 = MCV
# of RBC's
Normal Value: 80-94 u3 (cubic microns)
Clinical Implications:
The MCV indicates the relative size of the RBC's. It does not
indicate anything else about the cell. Several different types of
anemias can be classified as micro- or macrocytic anemias. This test
can direct the MD toward those types of anemias which alter the MCV
results.
- microcytic anemia.......decreased MCV (small cells)
- macrocytic anemia.......increased MCV (large cells)
2. MCH - Mean Corpuscular Hemoglobin: (Weight of hemoglobin in each cell)
calculated by:
Hgb x 10 = MCH
# of RBC's
Normal Value: 27-31 uuGrams (micro micro Grams)
3. MCHC - Mean Corpuscular Hemoglobin Concentration
Concentration of hemoglobin in the average RBC
calculated by:
Hgb x 10 = MCHC
Hct
Clinical Implications:
The MCHC is dependent upon the size of the RBC as well as the amount
of hemoglobin in each cell. Certain diseases and anemias will alter the
RBC count and/or the amount of hemoglobin in the cell. The MCHC is not
as dependent upon the RBC count as the other tests in this section.
Therefore, the MCHC can be useful for the diagnosis of such conditions
which are not dependent upon the number of RBC's.
The nursing implications for these tests are numerous. To the nurse,
most cases of anemia are quite apparent. They are caused by
hemorrhage, malnutrition, etc. However, the Indices can be used to help
diagnose the less common types of anemias. Nursing care will then be
determined according to the needs of that particular patient.
Test: Reticulocyte Count (Retic count)
This is a test for the estimation of the actual numbers of reticulocytes in the blood. Reticulocytes are the immature RBC's.
Normal Values: approx 1% of normal RBC count (50,000); Results vary; range 0.5% to 1.5%
Clinical Implications:
The retic count is an indication of the production of RBC's by the
bone marrow. An increase from the normal, usually indicates the body is
responding to such pathologies as hemorrhage, anemia, hemolysis, or
other such disease process. Decreased retic count may be indicative of
aplastic anemia or any related disease.
The retic count is also examined for those persons working near any
type of radioactive materials. The nurse should remember that the body
tries to compensate for such conditions as the hemolytic and macrocytic
conditions mentioned above. A large number of retics will be seen after
the treatment has begun for pernicious anemia, in which large numbers
will be produced as an attempt to bring to maturity, large numbers of
RBC's.
Test: Sickle Cell Test
The sickle cell test, also known as the Hb S test, is used to detect
sickle cells, which are severely deformed, rigid erythrocytes that may
slow blood flow. Sickle cell trait (characterized by heterozygous Hb S)
is found almost exclusively in people of African ancestry. It is
present in nearly 8% of African Americans.
Although this test is useful as a rapid screening procedure, it may
produce erroneous results. Hb electrophoresis should be performed to
confirm the diagnosis if sickle cell disease is strongly suspected.
**See Hemoglobin electrophoresis test earlier in this chapter.
Test: Iron and Total Iron-binding Capacity
Iron is essential to the formation and function of hemoglobin, as
well as many other heme and nonheme compounds. After iron is absorbed
by the intestine, it is distributed to various body compartments for
synthesis, storage, and transport. Serum iron concentration is normally
highest in the morning and declines progressively during the day.
Thus, the sample should be drawn in the morning.
An iron assay is used to measure the amount of iron bound to
transferrin in blood plasma. Total iron-binding capacity (TIBC)
measures the amount of iron that would appear in plasma if all the
transferrin were saturated with iron.
Serum iron and TIBC are of greater diagnostic usefulness when
performed with the serum ferritin assay, but together, these tests may
not accurately reflect the state of other iron compartments, such as
myoglobin iron and the labile iron pool. Bone marrow or liver biopsy,
and iron absorption or excretion studies may yield more information.
Normal Values:
Serum Iron:
males: 50 to 150 u/g/dl
females: 35 to 145 ug/dl
TIBC, Total Iron-binding capacity:
males and females: 250 to 400 ug/dl
Saturation:
males and females: 14% to 50%
Test: Ferritin
Ferritin is a major iron-storing protein found in reticuloendothelial
cells. It normally appears in small quantities in serum. In healthy
adults, serum ferritin levels are directly related to the amount of
available iron stored in the body and can be measured accurately by
radioimmunoassay.
Normal Values:
Men: 20 to 300 NG/ml
Women: 20 to 120 NG/ml
| 6 mo to 15 yr |
7 to 140 NG/ml |
| 2 to 5 months |
50 to 200 NG/ml |
| 1 month old |
200 to 600 NG/ml |
| Neonates |
25 to 200 NG/ml |
Normal serum Ferritin values will vary with age. Remember to check
with your lab, as normal values may be different in different labs. The
blood is collected via venipuncture in a standard 10-ml red-top tube. A
random blood specimen is used. No special instructions need to be
given to the patient except for explaining the procedure. Recent blood
transfusions may elevate serum ferritin levels.
Increased Serum Ferritin Levels: may indicate acute or chronic
hepatic disease, iron overload, leukemia, acute or chronic infection or
inflammation, Hodgkin's Disease, or chronic hemolytic anemias.
Slight increase, or normal Ferritin Level: may indicate chronic renal disease
Decreased serum Ferritin Levels: may indicate chronic iron deficiency
Test: ESR--Erythrocyte Sedimentation Rate
The ESR measures the time required for erythrocytes from a whole
blood sample to settle to the bottom of a vertical tube. Factors
influencing the ESR include red cell volume, surface area, density,
aggregation, and surface charge. The sample must be examined within 2
hours of collection and it must be handled gently, no clotting of sample
must take place.
Normal values: 0-20 mm/hr (gradually increase with age)
The ESR is a sensitive, but nonspecific test that is frequently the
earliest indicator of disease. It often rises significantly in
widespread inflammatory disorders due to infection or autoimmune
mechanisms. Such elevations may be prolonged in localized inflammation
and malignancies.
Increased ESR: may indicate pregnancy, acute or chronic inflammation,
tuberculosis, rheumatic fever, paraproteinemias, rheumatoid arthritis,
some malignancies, or anemia.
Decreased ESR: may indicate polycythemia, sickle cell anemia, hyperviscosity, or low plasma protein.
Test: Osmotic Fragility
Osmotic fragility measures red blood cell (RBC) resistance to
hemolysis when exposed to a series of increasingly dilute saline
solutions. The sooner hemolysis occurs, the greater the osmotic
fragility of the cells.
Purpose of test - The purpose of this test is to help diagnose
hereditary spherocytosis and to supplement a stained cell examination to
detect morphologic RBC abnormalities.
Normal results: Osmotic fragility values (percentage of RBC's
hemolyzed) are determined by the tonicity of the saline. Reference
values for the different tonicities are as follows:
0.5 g/dl sodium chloride (NaCl) solution (unincubated)
males: 0.5% to 24.7% hemolysis
females: 0% to 23.1% hemolysis
0.6 g/dl sodium chloride solution (incubated)
males: 18% to 55.2% hemolysis
females: 2.2% to 59.3% hemolysis
0.65 g/dl sodium chloride solution (incubated)
males: 4% to 24.8% hemolysis
females: 0.5% to 28.9% hemolysis
0.75 g/dl sodium chloride solution (incubated)
males: 0.5% to 8.5% hemolysis
females: 0.1% to 9.3% hemolysis
Low osmotic fragility (increased resistance to hemolysis) is
characteristic of thalassemia, iron deficiency anemia, and other red
blood cell disorders in which codocytes (target cells) and leptocytes
are found. Low osmotic fragility also occurs after splenectomy.
High osmotic fragility (increased tendency to hemolysis) occurs in
hereditary spherocytosis, in spherocytosis associated with autoimmune
hemolytic anemia, severe burns, chemical poisoning, or in hemolytic
disease of the newborn (erythroblastosis fetalis).
Test: WBC count--White Blood Cell Count (Leukocyte count)
A laboratory test that counts the actual number of WBC's in the blood.
Normal Values: total WBC: 4,500 to 10,500
BASIC TYPES OF WBC'S:
- neutrophils (granulocyte)
- lymphocytes (non-granulocyte)
- monocytes (non-granulocyte)
- eosinophils (granulocyte)
- basophils (granulocyte)
Clinical Implications:
As we all know, WBC's are our body's first line of defense against
invading bacteria and most other harmful organisms. This test (WBC),
measures the total number of all types of WBC's. Further examination of
the different types and numbers of cells present, could tell much about
the state of the body's defense system. WBC count will normally vary
as much as 2,000 on any given day.
Test: Differential Cell Count also known as "diff" or "differential"
Laboratory test that counts actual numbers of different types of WBC's.
Clinical Implications:
The following chart gives the normal values for each type of WBC.
Interpretation of the results of the differential must always be done
with the total number of WBC's in mind.
The WBC differential evaluates the distribution and morphology of
white blood cells. Therefore, it provides more specific information
about a patient's immune system than the WBC count alone. In the
differential test, the lab classifies 100 or more white cells in a
stained film of peripheral blood according to two major types of
leukocytes. They are: (1) Granulocytes (neutrophils, eosinophils,
basophils); (2) non-Granulocytes (lymphocytes, monocytes). The
percentage of each type is then determined.
The differential count is the relative number of each type of white
cell in the blood. By multiplying the percentage value of each type, by
the total WBC count, the lab obtains the absolute number of each type
of white cell. Although little is known about the function of
eosinophils in the blood, abnormally high levels of them are associated
with various types of allergic disorders and reactions to parasites. In
such cases, the eosinophil count is sometimes ordered as a follow-up to
the white cell differential. This test is also appropriate if the
differential WBC count shows a depressed eosinophil level.
Interpreting the Differential
In order to interpret the results of the WBC and the Differential,
the nurse must consider both relative and absolute values of the
differential. Considered alone, relative results may point to one
disease while masking the true pathology that would be revealed by
considering the results of the white cell count.
For example, consider a patient whose white blood cell (WBC) count is
6000/ul and whose differential shows 30% neutrophils and 70%
lymphocytes. His relative lymphocyte count would seem to be quite high
(lymphocytosis), but when this figure is multiplied by his white cell
count (6000 x 70% = 4,200 lymphocytes/ul), it is well within normal
range.
The patient's neutrophil count, however, is low (30%), and when this
is multiplied by the white cell count (6,000 x 30% = 1,800
neutrophils/ul), the result is a low absolute number. This low result
indicates decreased neutrophil production, which may mean depressed bone
marrow.
| CELL |
ADULT |
ABSOLUTE |
RELATIVE VALUE (6-18 years old) |
| TYPE |
VALUE |
VALUE |
BOYS |
GIRLS |
|
| Neutrophils |
47.6% to 76.8% |
1,950 to 8,400/ul |
38.5% to 71.5% |
41.9% to 76.5% |
| Lymphocytes |
16.2% to 43% |
660 to 4,600/ul |
19.4% to 51.4% |
16.3% to 46.7% |
| Monocytes |
0.6% to 9.6% |
24 to 960/ul |
1.1% to 11.6% |
0.9% to 9.9% |
| Eosinophils |
0.3% to 7% |
12 to 760/ul |
1% to 8.1% |
0.8% to 8.3% |
| Basophils |
0.3% to 2% |
12 to 200/ul |
0.25% to 1.3% |
0.3% to1.4% |
NEUTROPHILS:
Increased by:
- Infection; gonorrhea, osteomyelitis, otitis media, chickenpox, herpes, others
- Ischemic necrosis due to MI, burns, carcinoma
- Metabolic Disorders; diabetic acidosis, eclampsia, uremia, thyrotoxicosis
- Stress Response; due to acute hemorrhage, surgery, emotional distress, others
- Inflammatory disease; rheumatic fever, acute gout, vasculitis, myositis
Decreased by:
- Bone marrow depression; due to radiation or cytotoxic drugs
- Infections; such as typhoid, hepatitis, influenza, measles, mumps, rubella
- hypersplenism; hepatic disease, storage disease
- Collagen vascular disease; systemic lupus erythematosus
- Deficiency of; folic acid or vitamin B12
EOSINOPHILS:
Increased by:
- Allergic disorders; asthma, hay fever, food or drug sensitivity, others
- Parasitic infections; trichinosis, hookworm, roundworm, amebiasis
- Skin Diseases; eczema, psoriasis, dermatitis, herpes, pemphigus
- Neoplastic diseases; Hodgkin's disease, chronic myelocytic leukemia
- Miscellaneous; collagen vascular disease, ulcerative colitis, pernicious anemia, scarlet fever, excessive exercise, others
Decreased by:
- Stress response; due to trauma, shock, burns, surgery, mental distress, Cushing's Syndrome
BASOPHILS:
Increased by:
- Miscellaneous disorders; Chronic myelocytic leukemia, polycythemia
vera, some chronic hemolytic anemias, Hodgkin's disease, myxedema,
ulcerative colitis, chronic hypersensitivity states,
Decreased by:
- Miscellaneous disorders; hyperthyroidism, ovulation, pregnancy, stress
LYMPHOCYTES:
Increased by:
- Infections; pertussis, syphilis, tuberculosis, hepatitis, mumps, others
- Others; thyrotoxicosis, hypoadrenalism, ulcerative colitis, immune diseases
Decreased by:
- Severe debilitating illness; congestive heart failure, renal failure, advanced tuberculosis
- Others; Defective lymphatic circulation, high levels of adrenal Corticosteriods, others
MONOCYTES:
Increased by:
- Infections; subacute bacterial endocarditis, tuberculosis, hepatitis, malaria
- Collagen vascular disease; systemic lupus erythematosis, rheumatoid arthritis
- Carcinomas; monocytic leukemia, lymphomas
Decreased by: (unknown)
HEMATOLOGY................In Summary
RBC lab values, along with the indices, are used to diagnose anemia
and to define the type of anemia present. The lab values are calculated
and compared for the individual characteristics of the blood cells.
When the individual characteristics of the cells are determined, you
can then decide if the condition is hemorrhagic or another type of
anemia.
One should ask the following questions in order to isolate the type of anemia:
- Are the reticulocytes increased?
possible hemorrhage
- Is the hemoglobin abnormal?
possible factor anemia
possible hemorrhage
- Is the RBC normal?
possible metastatic problem
possible hemorrhage
Coagulation Studies
Nursing implications related to clotting studies are numerous. An
increase in clotting of blood or a decrease in clotting ability will be
considered the two main problems of coagulation of the blood.
Following is a summary of the overall phases of blood clotting.
Circulating blood generally has two main inactive proteins relating to
clotting. These are prothrombin and fibrinogen. It must also be
remembered that platelets stimulate the clotting process.
Blood Clotting Process
| PHASE I |
Initiation Phase
platelets plus initiation factor
|
| PHASE II |
Thromboplastin Phase
* platelet factors plus Calcium
* plus factors 8, 9, 10, 11, 12
.....yields thromboplastin
|
| PHASE III |
Thrombin Phase
*prothrombin plus calcium
*plus thromboplastin
*plus accelerator factors 5, 7, 10
..........yields Thrombin
|
| PHASE IV |
Fibrin Phase
*fibrinogen plus factor 8
*plus Thrombin
.........yields Fibrin CLOT |
Test: Platelet Count
A test which is a direct count of platelets (thrombocytes) in whole blood.
Normal Values: 150,000 to 350,000 per mm3 (cubic mm)
Clinical Implications:
- Platelets are the smallest formed elements in the blood. They are
vital to the formation of the hemostatic plug in vascular injury. They
promote coagulation by supplying phospholipids to the intrinsic
thromboplastin pathway.
- Thrombocytopenia - decreased platelet count, below approx 100,000
- Spontaneous bleeding - if platelets decreased below approx 50,000
- Fatal GI bleeding or CNS hemorrhage - if platelets below approx 5,000
- When the platelet count is abnormal, diagnosis usually requires
further studies, such as CBC, bone marrow biopsy, direct antiglobulin
test (direct Coomb's test), and serum protein electrophoresis.
- Use a 7-ml lavender-top tube for collection. A random specimen is
used. Mix the blood GENTLY with the anticoagulant in the tube. Rough
handling will interfere with the results.
- Hemolysis due to rough handling or to excessive probing at the venipuncture site may alter test results.
- Many medications will decrease platelet count; they include
acetazolamide, acetohexamide, antimony, antineoplastic drugs,
brompheniramine maleate, carbamazepine, chloramphenicol, furosemide,
gold salts, isoniazid, mephentoin, methyldopa, sulfonamides, thiazide,
and many others.
Platelets normally increase in persons living at high altitudes for
extended periods of time. They also increase with persistent cold
temperatures, and during strenuous exercise and excitement. The count
decreases just prior to menstruation.
Test: Prothrombin Time PT or Pro Time
This test is a measure of phase III of the clotting process. The PT
may give false readings due to some other clotting defects. However, it
is usually indicative of a phase III problem.
Normal values: (child or adult): 11-15 seconds or 70%-100% (depends on method used)
Clinical Implications:
Prothrombin is also known as factor II of the coagulation factors.
It is produced by the liver and requires vitamin K for its synthesis.
In liver disease, PT is usually prolonged. The test requires 7 to 10 ml
of blood with an anticoagulant in the blood tube. It can be collected
in a black-top tube (sodium oxalate in the tube), or blue-top tube
(sodium citrate in the tube). The most common is the blue-top tube, the
specimen must be tested within 4 hours of collection and is usually
packed in ice and delivered to the lab quickly. This is a very common
lab test and is usually performed as a routine hospital admission
screening test. A high-fat diet may cause decreased PT, and alcohol
can cause an increased PT result.
Test: Partial Thromboplastin Time PTT
A test similar to the PT, the PTT is also used to detect clotting
abnormalities. APTT, Activated PTT, similar to PTT but is more
sensitive than PTT test; it will help to identify the defective factor,
if one is defective.
Normal Values:
PTT: 60-70 seconds
APTT: 30-45 seconds
*these results may vary due to test methods in different hospitals.
Clinical Implications:
The PTT is very similar to the PT. It is used to detect Phase II
defects in the clotting process. It will usually detect deficiencies in
all clotting factors except factors VII and XIII. It is usually
performed for monitoring Heparin therapy. Heparin doses are usually
adjusted according to the PTT test results. The PTT is usually more
sensitive than the PT test.
Test: Bleeding Time
A raw measurement of the time needed for an artificially produced skin puncture to stop bleeding.
Normal Values:
Ivy method: 1-6 minutes
Duke method: 1-3 minutes
Clinical Implications:
Hodgkin's disease is suspected if there is decreased bleeding time.
Prolonged rate may indicate: thrombocytopenic purpura, platelet
abnormality, vascular abnormality, leukemia, severe liver disease, DIC
disease, aplastic anemia, factor deficiencies (V, VII, XI), Christmas
disease, hemophilia. The following drugs can affect bleeding time:
aspirin, dextran, mithramycin, coumadin, streptokinase-streptodornase
(fibrinolytic agent). Aspirin, alcohol, and also anticoagulants may
increase bleeding time.
This test is usually inconclusive. It can however, be helpful for
diagnosing capillary abnormalities and other disorders. For detecting
other clotting problems, this test will usually show a normal result.
This test is usually just a general screening test.
Test: TGT, Thromboplastin Generation Time
A test for phase II clotting defects. It tests the ability of the patient to produce thromboplastin.
Clinical Implications:
This test is very complicated and only a few large laboratories will
perform this test. The TGT has the ability to exactly pinpoint the
defect in the clotting process. This fact can make the TGT a very
valuable test under certain circumstances.
Test: Plasma Fibrinogen
A test for the level of circulating plasma fibrinogen.
Clinical Implications:
This test can be very valuable for helping diagnose disorders which
can cause lowered levels of the fibrinogen. It is also useful for
detecting substances which destroy fibrinogen (fibrinolysins).
Discussion of Coagulation Tests
The tests mentioned here are commonly used in hospitals today. There
are many other coagulation tests available, most of which are
complicated, expensive, and usually only performed at large medical
centers. Many of those specialized tests are used only after simpler
screening tests are performed.
The nurse should always remember to obtain a very detailed history
from the patient. The history can be most useful in helping the MD make
an accurate diagnosis.
Many times the patient may not speak freely with the physician or may
have forgotten some important detail or symptom. An observant nurse
can possibly help with the medical diagnosis and possibly save the
patient extra hospitalization and/or unnecessary testing.
As far as the mechanics of the tests are concerned, there is little
for the nurse to do in order to prepare the patients. The nurse should
always "warn" the patient that the blood will be drawn, or that they
will be injected with something, if it is part of the test. However,
most coagulation studies are done with a specimen of blood drawn either
randomly or at a special time of the day.
The specimen of blood will probably have an anticoagulant in it or in
the collection tube and most specimens will either have to be iced or
brought to the lab quickly for analysis.
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