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General Principles
 Labs are usually collected in the early morning…if to be done in a
fasting state withhold food and fluids for 8-12 hours before the test
 Collect using standard precautions to protect against exposure to
blood or body fluids; use strict aseptic technique to protect patient
from infection
 Label specimens: name, date, time of collection, type of specimen
 On lab requisition slip: diagnosis, medical record number, any factors
that could interfere with test results such as foods or prescribed drugs
 Avoid agitation of the blood specimens to prevent hemolysis and send
promptly to lab
 Values in the reference range are considered normal; reference ranges
vary
 Critical values are abnormal values that could increase risk of harm to
client; sent immediately to the nursing unit and must be reported to
the charge nurse and/or health care provider

Twenty four hour Urine specimens

 Obtain container with preservative, if needed, from the lab
 Hang signs in patient room notifying 24 hour urine collection
 Discard first urine
 Obtain all other urines for 24 hours and keep in fridge or on ice
 Send to lab promptly

Glucose Tolerance Test

 Screening test for DM
 Patient teaching:
o Eat high carbohydrate diet 200-300 grams daily for 3 days prior
to the test
o Do not drink alcohol or coffee or smoke for 36 hours before the
test
o Fast for 10-16 hours before the test as instructed by PCP
o Do not exercise for 8 hours before or after the test; sit quietly
during the test
o Baseline glucose level; ingest oral or IV glucose load, and a
series of blood glucose samples
Fasting blood glucose 70-110
Random glucose 60-110 anything above 150 warrants further
testing
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GTT one hour should be less than 200

GTT at two hours should be 70-120 or nearly back to baseline
Glycosolated hemoglobin normal is 3.5 to 6
Good diabetic control 7 or less
Fair diabetic control 7-8
Poor diabetic control greater than 8

 Glycosolated hemoglobin measures glycemic control over three to five

weeks (takes into account continuous production and destruction of
red blood cells); some sources report 3-4 months due to lifespan of red
blood cell
Coagulation Studies
PT and INR
 Measures time needed for prothrombin ( a vitamin K dependent
glycoprotein produced in the liver) to form a fibrin clot via the extrinsic
clotting pathway
 Commonly used to assess effectiveness of warfarin or to diagnose DIC,
Vitamin K deficiency, or liver dysfunction
 Normal PT is 11-13 and therapeutic is 1.5 to 2 times the normal
 Teach client to maintain a steady but moderate intake of green leafy
vegetables
aPTT
 Measures time needed for recalcified, citrated plasma to clot after
adding activated thromboplastin reagent; reflects intrinsic clotting
pathway
 Commonly used to assess heparin therapy; can screen for all clotting
deficiencies except factor 7 and 13
 Elevated in liver disease and DIC
 Normal range is 20-35 seconds; therapeutic is 1.5 to 2.5 normal
 Do not draw lab sample from the same arm where the heparin is
infusing
 Low values indicate ineffective therapy and high vales indicate risk for
bleeding or hemorrhage
Bleeding time
 Evaluates overall functioning of platelets in achieving hemostasis
 Skin puncture is done to determine time needed for bleeding to stop
 Normal reference range is 1-5 minutes; depending on the type of
method used
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 Ensure patient has not received any medications that would interfere
with the test for three days prior; apply pressure dressing after
procedure if needed
Ddimer
 Evaluates for hypercoagulability by assessing secondary fibrinolysis
that yields fibrin degradation fragments
 Normal value is 0-3; results are increased in DIC, DVT, PE, and arterial
or venous thromboses
CBC
 Discussed last week; review normocytic and normochromic versus
micro and macro
 A shift to the left indicates more immature neutrophils being
released due to a more rapid production to combat inflammation or
infection
 Shift to the right indicates cells with excessive nuclear segments
seen in liver disease, megaloblastic and pernicious anemias, and
Down syndrome
 Eosinophils go up with allergic and parasitic conditions and
decrease with higher levels of steroids
 Basophils increase during the healing process and decrease when
steroid levels rise
 Monocytes are the second line of defense against bacterial infection
and foreign substance; monocytes ingest larger particles and debris
from cellular destruction and may also kill tumor cells but the
mechanism is unclear
 Lymphocytes elevate during chronic and viral infections and
lymphocytic leukemia where B and T lymphocytes increase
Lipids
Cholesterol less than 200
LDL less than 130 and less than 110 with known CAD
HDL 60 or greater
Triglycerides less than 200 and less than 150 with known CAD
CK begins to rise 4-6 hours after myocardial or skeletal muscle damage;
peaks at 18-24 hours; returns to normal within 3-4 days
CK is 55-170 for males and 30-135 for females
CK-MB – cardiac band 0-6
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CK-MM skeletal muscle band 94-100

CK-BB is brain tissue band 0
Troponin is a regulatory protein found in skeletal and cardiac muscle in
striated muscle cells; Usually monitor results over three days and correlate
with clinical picture
Troponin I is less than 0.05
Tropinin T is less than 0.3
Troponin will rise within 3 hours of myocardial infarction; returns to normal in
5-8 days (I) 10-14 days (T)
Natriuretic peptides
Neuroendocrine peptides useful in identifying and monitoring heart failure
Atrial NP is secreted in response to atrial stretch or endocrine stimulation via
the renin aldosterone system
Brain NP is secreted in response to ventricular stretch or endocrine
stimulation via the renin aldosterone system; there is a positive correlation
between dyspnea as a sign of heart failure and rising BNP levels
C-type NP is produced by vascular endothelial cells and has vasodilative
properties

Thyroid function studies

Decreased T4 and elevated TSH is consistent with a thyroid disorder
Decreased T4 and decreased TSH is consistent with a pituitary disorder
T3 is useful for diagnosing hyperthyroidism
If high TSH, T3 and T4 are low then it is hypothyroidism
If low TSH and high T3T4 then it is hyperthyroidism
Renal Function Studies
BUN
Formed in liver as an end product of protein metabolism consists of nitrogen
portion of urea
Excreted via kidneys with only small amounts reabsorbed in the renal
tubules
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Normal is 8-22
Rises with reduced glomerular filtration rate, increased dietary protein,
increased catabolism – starvation or malnutrition, crush injuries, febrile
illness, dehydration with hemoconcentration
Decreases with overhydration, inadequate protein intake, severe liver
disease (inadequate conversion of ammonia to urea)
Assess concurrently with creatinine for true indication of renal status
If both BUN and Creatinine are elevated – there is real insufficiency or failure
Creatinine
End product of muscle creatinine metabolism; indicator of GFR and renal
status
Elevated with renal insufficiency and failure
Teach client to avoid red meat for 24 hours before test and heavy exercise
for 8 hours prior to test to avoid falsely elevated values
Normal reference range is 0.6 to 1.3
Creatinine Clearance
Compares serum creatinine with creatinine excreted in a volume of urine
over a period of hours (2, 12, 24)
Collection is the same as for a 24 hour urine; no preservative is needed
Normal is 85-125 in men and 75-115 in women; decreases with renal
insufficience and failure
Serum osmolality
Reflects concentration of serum
Can be calculated using sodium, BUN, and blood glucose levels but
frequently is less than a drawn value
Values rise with dehydration and decrease with fluid volume overload
Serum osmolality is usually 280-300
Formula is 2 times sodium plus BUN divided by 2.8 plus glucose divided by
18
2(NA of 137) plus 10 BUN/2.8 plus 110 glucose/18
276 + 3.57+6.11 = 286
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Urine Osmolality
Measures the concentration of the urine; high values indicate kidneys are
conserving water while low values may reflect increased fluid intake, the
effect of diuretics, diabetes insipidus, or renal damage; need to correlate
with the clinical picture
Normal is 250-900
Urinalysis
Color – pale yellow to amber
Clarity – clear
Odor – faint aromatic
Specific gravity – 1.010 to 1.025
pH 4.5 to 8
Protein – absent
Glucose – absent
Ketones – absent
Sediment – 0-3 RBCs, 0-4 WBCs, occasional renal epithelial cell
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Liver Function Studies

ALT (alanine aminotransferase)
Found primarily in liver cells; also found in small amounts in heart, kidney,
and skeletal muscle
Normal range is 10-25
Rises as high as 200-400 with hepatitis or liver damage from drugs or
chemicals
Used to differentiate jaundice caused by liver disease (greater than 300) and
causes outside the liver (less than 300)
There is no food or fluid restriction before the test.
AST (aspartate aminotransferase)
Found mainly in heart muscle and liver, with moderate amounts found in
skeletal muscle, kidneys, and pancreas
Normal range is 8-38
Rises with cellular injury and release of enzyme into circulation so rises with
liver injury or disease, MI, pancreatitis, and musculoskeletal trauma
False elevations can be caused by IM injections
Bilirubin
Normal
Total Bilirubin: 0.1 to 1.2 in adults and 1 to 11.7 in neonates
Direct (conjugated) Bilirubin: 0.1 to 0.3 in adults and less than 0.6 in
neonates
Indirect (unconjugated) Bilirubin: subtract direct from total
Bilirubin is a byproduct of hemoglobin breakdown; also bilirubin is produced
by liver, spleen and bone marrow
Ammonia
Normal 35-65
End product of nitrogen breakdown during protein metabolism
Metabolized by the liver and excreted by the kidneys
Elevated results indicate liver disease and possible encephalopathy – degree
of elevation does not correlate directly with risk for hepatic coma
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Teach to not smoke for 24 hours prior to test and to fast except for water for
8-10 hours before test
Pancreatic Enzymes
Amylase is produced by pancreas and salivary glands for carbohydrate
digestion and excreted by the kidneys
Normal is 25-151
Increased with pancreatitis, elevation begins within 3-6 hours after pain
begins, peaks in 24 hours, and returns to normal in 2-3 days
Many drugs affect results so list medications on lab requisition
If a radiopaque dye study was done (cholecystography) can cause false
results for up to 72 hours after the dye study.
Lipase is produced by the pancreas to break down fats and triglycerides into
fatty acids and glycerol
Normal is 10-140
Increased with pancreatic disorders; may rise as late as 24-36 hours after
onset and return to normal as much as 14 days later

Metabolic Function Studies

Albumin
Plasma protein that maintains oncotic pressure (to prevent edema) and
transports water soluble substances like fatty acids, hormones, bilirubin, and
medications
Normal is 3.4-5
May be decreased if malnourished; monitor as an indicator of nutritional
status
Total Protein
Consists of circulating albumin and globulins in serum; serves many
functions including tissue growth and repair, pH buffering, enzymes,
hormones, and coagulation factors
Normal is 6-8
May be decreased with malnutrition, low protein diet, GI disorders, severe
liver disease, chronic renal failure, severe burns, and water intoxication
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May be increased with dehydration (hemoconcentration), vomiting, diarrhea

Teach to avoid high fat foods for 24 hours before test to avoid false results
Pre-albumin
Sensitive indicator of recent changes in catabolism as half life is less than 2
days
Used to screen for nutritional problems and to gauge effectiveness of
nutrition therapy
Normal is 3.4-5
Low values indicate need for comprehensive nutritional evaluation
High values are found in renal failure due to poor renal excretion
Alkaline Phosphatase
Enzyme present in intestines, liver, bone, and placenta
Normal is 4.5 to 13
Rises with periods of bone growth and with liver disease or bile duct
obstruction
May be affected by hepatotoxic drugs administered 12 hours prior to test
Uric Acid
Byproduct of purine metabolism; elevated in gout; affected by diet and renal
function
Normal is 4-8 in males and 3.5 to 7.3 in females
Excessive uric acid can lead to kidney stone formation as renal clearance
occurs
Avoid high purine foods such as organ meats, scallps, sardines, etc.
Immune function tests
HIV
Testing for HIV includes the enzyme linked immunoabsorbent assay (ELISA),
Western blot, immunoflouroescence assay (IFA), and HIV type 1 and type 2
antibodies immunoassay
Elisa is tested first and repeated in duplicate if positive with the same blood
sample; if one test is negative, client is retested in 3-6 months
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If both tests are positive, then a positive western blot would confirm the
results; if the western blot or the IFA is negative; repeat testing should be
done in 3-6 months
The last two tests were recently approved and test for specific antibodies
and follow algorithms to determine test results

CD4 T cells
Function of T helper cells is primarily to help B cells and increase
immunoglobulin production
Normal is 500-1600
Decreases with HIV causing increased risk of infection at 200-499 and severe
risk if less than 200
CD4 to CD8 ratio
CD8 or T suppressor cells are responsible for the down regulation of immune
response or once an infection has been eradicated
Normal ratio of CD4 to CDD8 cells is 2 to 1
With a decrease in CD4 counts, HIV progresses, and client condition worsens,
and this ratio decreases.
Viral load testing
Measures amounts of HIV viral RNA or other viral protein in blood
Values increase or decrease according to current level of infection

Therapeutic drug levels

Acetaminophen 10-20
Amitriptyline 120-150
Carbamazepine 5-12
Clozapine 1000-2000
Digoxin 0.5 to 2.0
Gentamicin 5-10
Lidocaine 1.5 to 5.0
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Lithium 0.5-1.3
Magnesium 4-7
Phenytoin 10-20
Procainamide 4-10
Salicylate 100-250
Theophylline 10-20
Valproic acid 50-100
Vancomycin 15-20