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II.D. LABORATORY AND DIAGNOSTIC TESTS

CLINICAL CHEMISTRY

1. Name of examination: Serum Sodium
Definition:
Sodium is the most abundant cat-ion in extracellular fluid, and along with its
accompanying chloride and bicarbonate an-ions. Sodium plays a major role in maintaining
homeostasis through a variety of functions, which includes maintenance of osmotic pressure of
extracellular fluid, regulation of renal retention and excretion of water, maintenance o acidbase balance, regulation of potassium and chloride levels, stimulation of neuromuscular
reactions, and maintenance of systemic blood pressure.
Purpose:
1. To monitor the sodium level
2. To detect sodium imbalance (hyponatremia or hypernatremia)
3. To compare the sodium level with that of other electrolytes
Specimen: serum
Preparation:
1. There are no restrictions on food and fluids. If the client has eaten large quantities of foods
high in salt content in the last 24-48 hours, this should be noted on the laboratory slip and the
health care provider should be notified. Sodium is rarely requested alone but is rather given as
part of the serum electrolytes.
2. Collect 3-5mL of the venous blood in a red-top tube.

Name

Normal Value

Sodium

135-148 mmol/L

Results

Significance

2. Name of examination: Serum potassium
Definition: potassium is the most abundant intracellular cat-ion; much smaller amounts are
found in the blood. Potassium is essential for the transmission of electrical impulses in cardiac
and skeletal muscle. In addition, it helps to maintain the osmolality and electroneutrality of
cells, functions in enzyme reactions that transform glucose into energy and amino acids into
proteins, and participates in the maintenance of acid-base balance.
Purpose:
1. To check the potassium level
2. To monitor potassium levels during health problems (ex. Renal insufficiency, debilitating
illness, cancer) and with certain drugs (thiazide diuretics)
3. Detect the presence of hypokalemia or hyperkalemia.
Preparation:
1. Food, fluid and drug restrictions are not necessary.
2. Collect 3-5mL of venous blood in a red top tube.
3. Avoid hemolysis

4. Avoid leaving the tourniquet on for greater than 2 minutes if possible.
Specimen: serum
Result

Name
Potassium

Normal value

Significance

3.5-5.3 mmol/L

3. Name of examination: Creatinine
Definition: creatinine is a nitrogenous waste resulting from protein metabolism.
Creatinine resides almost exclusively in skeletal muscles, where it participates in
energy-requiring metabolic reactions. In these processes, a small amount of creatinine
is irreversibly converted to creatinine, which then circulates the kidneys and is
excreted. The amount of creatinine generated in an individual is proportional to the
mass of te skeletal muscle present and remains fairly constant, unless there is massive
muscle damage resulting from crushing injury or degenerative muscle disease.
Purpose:
1. Assess a known r suspected disorder involving muscles in the absence of renal
disease.
2. Evaluate known or suspected impairment of renal function.
Preparation: obtain 3-5mL of venous blood. There are no food or fluid restrictions
before venipuncture. Drugs that influence normal creatinine levels include diuretics,
choral hydrate, sulfonamides, chloramphenicol, ascorbi acid and marijuana. A diet
high in red meat can cause abnormally high levels.
Result

Name
Creatinine

Normal value

Significance

53-115 umol/L

4. Name of examination: protime
Definition: prothrombin factor II converted to thrombin through the action of
thromboplastin which is needed to form acid. It is synthesized by the liver in a
process requiring vitamin k.
Purpose:
1. It is used to evaluate the extrinsic pathway of the coagulation sequence in patients
receiving oral warfarin or coumarin-type anticoagulants.
2. Identify the possible cause of abnormal bleeding, such as epistaxis, hematoma,
gingival bleeding, hematuria, and menorrhagia.
3. Differentiate between deficiencies of clotting factors II, V, VII and X, which
prolong the PT; and congenital coagulation.
4. Disorders such as hemophilia A (factor VIII), which do not alter the PT.
5. Evaluate the response to anticoagulation therapy with coumarin derivatives and
determine dosage required to achieve therapeutic results. Identify individuals who
may be prone to bleeding during surgical, obstetric, dental or invasive diagnostic
procedures.
6. Monitor the effects of conditions such as liver disease, protein deficiency, and fat
malabsorption on homeostasis.
Preparation:
1. Explain the procedure to the patient

2. Tell the patient that no fasting is required
3. Collect approximately 5 to 7 mL of venous blood in a blue top tube
4. Apply pressure to the venipuncture site
5. If the PT is greatly prolonged, evaluate the patient for bleeding tendencies.
Result

Name

Normal value

Patient
% activity
INR
Normal control

Significance

11.5-15.5 sec
75-101 %

5. Name of examination: serum calcium
Definition: calcium is the most abundant cat-ion in the body and participates in
virtually all vital processes. About half the total amount of calcium circulates as free
ions that participate in blood coagulation, neuromuscular conduction, intracellular
regulation, glandular secretion, and control of skeletal and cardiac muscle
contractility. The remaining calcium is bound to circulating proteins and plays
nonphysiological role.
Purpose:
1. Evaluate coagulation disorders to determine whether altered serum calcium level is
contributing to the problem.
2. Monitoring the effects of renal failure on calcium levels, which are usually
decreased in the disorder.
Preparation: a 5mL sample of venous blood is obtained in a plain collecting tube or
syringe. Food and drinks are not usually restricted before venipuncture or collection
of the specimen.
Date:
Name
Calcium

Result

Normal value
2.12-2.52 mmol/L

Significance

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