Download Module #6D – Clinical Laboratory Testing – Basic Clinical Chemistry

Unit #6D – Clinical
Laboratory Testing –
Basic Clinical Chemistry
Cecile Sanders, M.Ed.,
MT(ASCP),
CLS (NCA)
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
Purpose of Clinical Chemistry Tests
– Measure levels of substances found
normally in human blood that have biological
functions. Examples: Glucose, Calcium
– Detect or measure non-functional
metabolites or waste products. Examples:
Creatinine, Blood Urea Nitrogen (BUN)
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
– Detect or measure substances that
indicate cell damage or disease. Examples:
Liver enzymes, such as ALT, Cardiac
enzymes, such as CK-MB
– Detect or measure drugs or toxic
substances. Examples: Dilantin, Drugs of
abuse screen
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Types
of Specimens for Chemical
Analysis
– Whole blood, serum or plasma. The most
common specimen is serum, collected in a
tube with no anticoagulant so that the
blood will clot.
– Urine – often 24 hour collections
– Others – Cerebrospinal Spinal Fluid (CSF)
and other fluids
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Collection
and Handling of Blood
Specimens for Chemical Analysis
– Blood collection tubes for obtaining serum Serum Separator Tubes (SST) do not have
an anticoagulant but do contain a gel
substance which will form an interface
between the clot and the serum when the
blood specimen is centrifuged. These tubes
are sometimes referred to as “Tiger Tops”.
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
– Blood collection
tubes for obtaining
plasma
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
– Patient preparation; time of collection; &
effects of eating on chemistry analysis
 Some
specimens are increased or decreased
after eating (ex. Glucose, triglycerides), so it is
important to know what the test and collection
method call for. Specimens for these tests are
usually collected in a fasting state.
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Sometimes
serum or
plasma appears lipemia
(milky) after a patient
has eaten a fatty
meal. Lipemia affects
most chemistry
analyses. The blood
must be recollected
when the patient is
fasting.
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Clinical
Chemistry Tests
– Normal or Reference Values – range of
values for a particular chemistry test from
healthy individuals
– Chemistry Panel grouping – some tests are
“bundled” according to the system or organ
targeted. Examples: thyroid panel, liver
panel, cardiac panel, kidney panel, basic
metabolic panel, etc.
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Commonly
Performed Chemistry Tests
or Analytes
– Proteins – essential components of cells and
body fluids. Some made by body, others
acquired from diet. Provides information
about state of hydration, nutrition and liver
function, since most serum proteins are
made in the liver.
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
– Electrolytes – sometimes called “lytes”
 Includes
sodium (Na), potassium (K), chloride
(Cl) and bicarbonate (HCO3-)
 Collectively these have a great effect on
hydration, acid-base balance and osmotic
pressure as well as pH and heart and muscle
contraction
 Levels differ depending on if inside vs. outside
cells
 Important in transport of substances into and
out of cells
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
– Minerals
 Calcium
– Used in coagulation and muscle contraction
– 99% is in skeleton and is not metabolically active
– Influenced by vitamin D, parathyroid hormone,
estrogen and calcitonin
– Hypercalcemia – occurs in parathyroidism, bone
malignancies, hormone disorders, excessive vitamin D,
and acidosis; may cause kidney stones
– Hypocalcemia – can cause tetany; occurs in
hypoparathyroidism, vitamin D deficiency, poor
dietary absorption and kidney disease
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Phosphorus
– 80% in bone and rest in energy compounds such as
ATP
– Influenced by calcium and certain hormones
 Iron
– Essential for hemoglobin
– Deficiency results in anemia; may be caused by lack of
iron in diet, poor absorption, poor release of stored
iron or loss due to bleeding
– Increased in hemolytic anemia, increased iron intake
or blocked synthesis of iron-containing compounds,
such as in lead poisoning
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
– Kidney Function Tests
 Serum
Creatinine
– Best test for overall kidney function; not affected by
diet or hormone levels
– Waste product of muscle metabolism
– Serum creatinine rises when kidney function is
impaired
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 BUN
(Blood Urea Nitrogen)
– BUN is surplus amino acids that are converted to urea
and excreted by kidneys as a waste product
– BUN influenced by diet and hormones, so it is NOT as
good an indicator of renal function as serum
creatinine levels
– BUN increased in kidney disease, high protein diet,
and after administration of steroids
– BUN decreased in starvation, pregnancy and in
persons on a low protein diet
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Uric
Acid
– Formed from breakdown of nucleic acids and
excreted as a waste product by kidneys
– Increased in kidney disease, but most often used to
diagnosis gout (pain in joints, mainly big toe, due to
precipitated uric acid crystals)
– Also increased in increased cell destruction, such as
after massive radiation or chemotherapy
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
– Liver Function Tests
 Liver
functions:
– Synthesizes glycogen from glucose
– Makes plasma proteins (albumin, lipoproteins,
coagulation proteins)
– Forms cholesterol and degrades it into bile acids,
which emulsifies fats for absorption
– Stores iron, glycogen, vitamins and other substances
– Destroys old blood cells and recycles components of
hemoglobin
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Total
Bilirubin
– Waste production of hemoglobin breakdown
– Increased in excessive RBC breakdown, such as
hemolytic anemia, or impaired liver function or some
sort of obstruction, such as a tumor or gall stone
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Liver
Enzymes – levels increase following
damage to liver tissues
– Alkaline Phosphatase (ALP or AP) - Greatly increased
in liver tumors and lesions; moderately increased in
diseases such as hepatitis
– Alanine Aminotransferase (ALT; formerly called
SGPT) - Increases up to 10x in cirrhosis, infections or
tumors and up to 100x in viral or toxic hepatitis
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
– Asparate Aminotransferase (AST; formerly called
SGOT) - Increased in liver disease, but also in heart
attacks
– Gamma Glutamyl Transferase (GGT) - Often used to
monitor patients recovering from hepatitis and
cirrhosis
– Lactate Dehydrogenase (LD) - Increased in liver
disease and following heart attacks
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Cardiac
Function Tests
– Creatine Kinase (CK) - Widely used to diagnosis and
monitor heart attacks
– Troponins
 Only present in heart muscle, making it a more
accurate indicator of heart attack than CK
 Cardiac Troponin T (cTnT)
 Cardiac Troponin I (cTnI)
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Lipid
Metabolism Tests
– Cholesterol
 Present in all tissues
 Serves as the skeleton for many hormones
 Recommended to be less than 200 mg/dL in
adults)
 LDL = “bad” cholesterol; HDL = “good”
cholesterol
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
– Triglycerides
 Main storage form of lipids, comprising 95% of
fat tissue
 Hyperlipidemia – having high blood levels of
triglycerides – may increase risk of heart attack
 Carbohydrate
Metabolism Tests
– Glucose - Largely regulated by insulin
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 Thyroid
Function Tests
– Thyroid Stimulating Hormone (TSH) - Inverse
relationship to thyroid function (the higher the TSH,
the lower the thyroid function and vice versa)
– Other less common thyroid tests include T3 and T4
– Hypothyroidism – underactive thyroid gland
– Hyperthyroidism – overactive thyroid gland
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
 For
more information on most clinical
laboratory tests, visit:
http://www.labtestsonline.org/
Click on any lab test or condition or
disease and find all sorts of
information!
Unit #6D – Clinical Laboratory
Testing - Basic Clinical Chemistry
Photos of some clinical chemistry
laboratories