Download common laboratory values

COMMON LABORATORY
VALUES
STEPHANIE ZIELINSKI, CPNP, DNP
COMMON LABORATORY VALUES
• Laboratory tests are an integral part of every day
practice within health care.
• Lab work can help assess and diagnose patients with
both acute and chronic illness.
COMMON LABORATORY TESTS
• Complete Blood Count with Differential
• Basic Metabolic Profile
• Iron Studies (TIBC, Ferritin)
• Thyroid Studies (TSH, Free t4)
• Vitamin D
• Lipid Panel
COMMON LABORATORY TESTS
• Complete Blood Count with Differential aka “CBC with
Diff”
• Components of a CBC with differential:
Total red blood cell count (RBC)
Hemoglobin (Hgb)
Hematocrit (Hct)
Mean Corpuscular volume (MCV)
Red blood cell distribution width (RDW)
Total white blood cell count (WBC)
A count (%) of each type of white blood cell (Neutrophils,
Lymphocytes, Monocytes, Eosinophils, Basophils)
• Platelet count
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(The Mayo Clinic, 2016; Up to Date, 2016)
COMMON LABORATORY TESTS
• What does each finding mean?
• Total red blood cell count (RBC)- The count of the
number of circulating red blood cells in 1 mm3 of
peripheral venous blood.
• Hemoglobin (Hgb)- The measure of the amount of Hgb
in the blood. Hgb constitutes over 90% of red blood cells.
COMMON LABORATORY TESTS
• A decrease in Hgb concentration means the patient is
anemic.
• Anemia can be due to iron/B12/folate deficiency, blood
disorders or other underlying pathology.
• And increase in Hgb concentration means the patient is
polycythemic.
• Polycythemia can result from a large number of causes, including
cancer, lung disease, heart defects and other underlying
pathologies. Smoking and many lung conditions can cause an
elevated Hgb due to chronic hypoxia.
COMMON LABORATORY TESTS
• Hematocrit- The measure of the percentage of the total
blood volume that is made up by the red blood cells.
• Mean corpuscular volume (MCV)- a measure of the
average size of a red blood cell. The MCV is important in
classifying anemias:
• Normal MCV = normocytic anemia
• Decreased MCV = microcytic anemia
• Increased MCV = macrocytic anemia
COMMON LABORATORY TESTS
• Red blood cell distribution width- An indication of the
variation of the red blood cell size (anisocytosis).
• In general an elevated RDW (more variation in the size of the
RBC’s) is associated with anemias with various deficiencies such
as iron, B12 or folate deficiencies.
COMMON LABORATORY TESTS
• What does each type of anemia mean?
Macrocytic Anemia• In adults, common causes of macrocytic anemia are:
• Medications (ex: Zidovuidine, Hydroxyurea), folate deficiency,
abnormal RBC maturation (Ex: Leukemia), alcohol abuse, liver disease
and hypothyroidism
• In children common causes of macrocytic anemia are:
• Medications (anticonvulsants, Zidovudine and immunosuppresents),
Vitamin B12 and folate deficiencies, liver disease and hypothyroidism
COMMON LABORATORY TESTS
• What does each type of anemia mean?
Microcytic Anemia• In adults, common causes of microcytic anemia are:
• Reduced iron availability (iron deficiency, copper deficiency), Alpha
or beta thalassemia and anemia of inflammation (chronic disease).
• In children common causes of microcytic anemia are:
• Iron deficiency and thalassemia
COMMON LABORATORY TESTS
• What does each type of anemia mean?
Normocytic Anemia• In adults, common causes of normocytic anemia are:
• Systemic disorders, chronic renal disease
• In children common causes of normocytic anemia are:
• Hemolytic disease, blood loss, infection and medication
COMMON LABORATORY TESTS
• Testing for iron deficiency:
Total Iron Binding Capacity (TIBC)- Will be elevated when
a patient is anemic.
Ferritin- The cellular storage protein for iron. Iron
deficiency results in a low ferritin level. Iron deficiency is
the only clinical situation in which extremely low values
of serum ferritin are seen
COMMON LABORATORY TESTS
• White Blood Cells• Lymphocytes- Comprise about 30-40% of circulating
white blood cells.
• Atypical and an elevated number of lymphocytes can often be
seen following viral infections.
• Other causes of atypical lymphocytes or lymphocytosis can be
lymphoma or leukemia.
• If a patient has lymphocytosis in addition to thrombocytopenia,
neutropenia or anemia, this is concerning for malignancy. Patient
should be referred immediately for hematology/oncology evaluation.
COMMON LABORATORY TESTS
• Neutrophils- 40-60% of circulating white blood cells.
• Neutrophils mature in the following order:
Myeloblast -> promyelocyte -> myelocyte -> metamyelocyte -> band -> mature neutrophil.
CBC/blood smear results with any cells seen that are less mature
than a myelocyte are almost always associated with hematological
malignancy. This warrants immediate hematology/oncology
referral.
An increased number of bands is called a “left shift” and is often
associated with infection.
COMMON LABORATORY TESTS
• A low level of neutrophils is Neutropenia. A low level of
neutrophils can increase the risk of infection.
• Neutropenia can be caused by malignancy, immunosuppression
or be idiopathic.
• An elevated Neutrophil count (Neutrophilia) is most
commonly seen with infections, stress, smoking and
after exercise.
COMMON LABORATORY TESTS
• Basophils- Comprise <1% of total WBC. An elevated basophil
count is most commonly associated with myeloproliferative
disorders, hypersensitivity or inflammatory reactions,
hypothyroidism, and certain infections.
• Eosinophils- Normally present in small numbers (< 5% of
WBC’s). Elevated level can indicate allergic state or parasitic
infection. Less commonly it can indicate a malignancy.
• Monocytes- The largest of the WBC’s. Elevated monocyte
level is most commonly associated with infections,
autoimmune disorders, malignancy and blood disorders.
COMMON LABORATORY TESTS
Platelets
• Thrombocytopenia- (low platelet count)- Most commonly
seen due to medications (antibiotics, antiepileptics), infection,
blood disorders and liver disease.
• The presence of a very high platelet count, extremely large
platelets, and/or megakaryocyte fragments is abnormal and
often associated with an underlying malignancy.
COMMON LABORATORY TESTS
• Basic Metabolic Profile
• Comprised of:
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Sodium (Na)
Potassium (K)
Chloride (Cl)
Carbon Dioxide Content (CO2)
Blood Urea Nitrogen (BUN)
Serum Creatinine (Cr)
Serum Glucose (Glu)
Total Calcium (Calcium)
COMMON LABORATORY TESTS
• Sodium (Na)
• Hyponatremia- Sodium is low. This is not a common finding and is
often associated with heart failure, burns, malnutrition and severe
diarrhea.
• Hypernatremia- Sodium is elevated. This is commonly associated
with three main issues:
• Un-replaced water loss- diarrhea/vomiting, excessive sweating,
diabetes insipidus, diabetic ketoacidosis
• water loss into cells- usually transient, typically induced by
severe exercise or electroshock induced seizures.
• sodium overload- salt poisoning, hypertonic saline
administration
COMMON LABORATORY TESTS
Potassium (K)
Hypokalemia- A low level of potassium. Hypokalemia is most
commonly caused by the use of diuretics, severe burns, Cushing’s
syndrome, acute GI illness, hyper-aldosteronism, and renal disease.
COMMON LABORATORY TESTS
Potassium (K)
Hyperkalemia- Elevated potassium, caused by three main
mechanisms:
●Excessive increase in potassium intake
●Trans-cellular movement of intracellular potassium into
the extracellular space
●Decreased renal excretion of potassium
COMMON LABORATORY TESTS
Potassium (K)
●Excessive increase in potassium intake- typically caused
by a high potassium containing medication or IV fluid.
●Trans-cellular movement of intracellular potassium into
the extracellular space- metabolic acidosis or breakdown
of normal tissue or rapid cell lysis causing potassium to be
released into the extracellular space; ex. Renal failure,
tumor
lysis, rhabdomyolysis.
●Decreased renal excretion of potassium- Kidney disease
COMMON LABORATORY TESTS
Potassium (K)
*Remember: In children, psuedohyperkalemia can occur due to the
small needle size which can cause the blood sample to hemolyze
resulting in a falsely elevated potassium level.
COMMON LABORATORY TESTS
• Chloride
• Elevated Chloride Level- Dehydration, excessive salt intake,
kidney disease, hyperparathyroidism
• Low Chloride Level- occurs when there is too much water in
the body (ex: syndrome of inappropriate antidiuretic hormone),
Addison’s disease, Metabolic Alkalosis, heart failure.
COMMON LABORATORY TESTS
• Carbon Dioxide Content (CO2)aka “bicarb”
-Bicarbonate is an electrolyte, a negatively charged ion that is used
by the body to help maintain the body's acid-base (pH) balance.
-Acidosis and alkalosis describe the abnormal conditions that result
from an imbalance in the pH of the blood caused by an excess of
acid or alkali (base).
-Any disease or condition that affects the lungs, kidneys,
metabolism, or breathing has the potential to cause acidosis or
alkalosis.
COMMON LABORATORY TESTS
• Carbon Dioxide Content (CO2)aka “bicarb”
- Elevated CO2 can be caused by: Dehydration, Chronic diarrhea,
kidney disease, Addison’s disease, Diabetic Ketoacidosis
-Low CO2 can be caused by: severe prolonged vomiting, lung
disease (ex: COPD), heart failure, kidney disease
COMMON LABORATORY TESTS
• Blood Urea Nitrogen (BUN)
• Urea is formed in the liver as the end product of protein
metabolism and is transported to the kidneys for excretion.
• Nearly all renal diseases can cause an inadequate excretion of
urea, which causes the blood concentration to rise above normal
(thus an elevated BUN).
• The BUN is interpreted in conjunction with the creatinine test –
these tests are referred to as “renal function studies”.
COMMON LABORATORY TESTS
• Serum Creatinine
Creatinine is a catabolic product of creatine phosphate used in
skeletal muscle contraction.
Creatinine, as with blood urea nitrogen, is excreted entirely by the
kidneys and blood levels are therefore proportional to renal
excretory function.
An elevated Creatinine level is related to kidney disease or
decreased kidney function.
COMMON LABORATORY TESTS
• Glucose- This is one of the most commonly ordered blood
tests.
• Hyperglycemia (Elevated Glucose)- most commonly caused
by underlying diabetes, but can also be a result of significant
stress on the body or sepsis.
• Hypoglycemia (Low glucose)- Can be caused by underlying
diabetes, long term or excessive fasting, underlying
neurogenic disorder or severe illness/sepsis.
COMMON LABORATORY TESTS
• Serum Calcium
• The total serum calcium is a measure of both
• Free (ionized) calcium
• Protein bound (usually to albumin) calcium
• Calcium level is most influenced by parathyroid hormone (PTH),
vitamin D, the calcium ion, and phosphate.
Hypercalcemia (elevated calcium)- primary hyperparathyroidism
and malignancy are the most common causes.
Hypocalcemia (low calcium)- Disorders of PTH and Vitamin D are
the most common causes.
COMMON LABORATORY TESTS
• Thyroid Studies
• The Thyroid gland produced T3 and T4. The thyroid gland is stimulated
to produce these by Thyroid Stimulating Hormone (TSH) that is released
by the pituitary gland.
●A high TSH is often accompanied by a low Free T4. This is because the body
will typically increase the TSH to help increase a low T4 level. This is
typically indicative of hypothyroidism.
-If TSH and T4 are both low, this is indicative of a pituitary problem.
●Serum TSH low and T3/T4 are elevated, this is indicative of
hyperthyroidism.
COMMON LABORATORY TESTS
Vitamin D
• Low Vitamin D- most commonly caused by decreased
intake or absorption, reduced sun exposure.
• High Vitamin D- Very rare, typically seen when a
patient has ingested a high amount of vitamin d (dose
error or “fad” diet with high doses of supplements)
COMMON LABORATORY TESTS
Thyroid Studies
The Thyroid gland produced T3 and T4. The thyroid gland is stimulated to
produce these by Thyroid Stimulating Hormone (TSH) that is released by the
pituitary gland.
-A high TSH is often accompanied by a low Free T4. This is because the body
will typically increase the TSH to help increase a low T4 level. This is
typically indicative of hypothyroidism.
-If TSH and T4 are both low, this is indicative of a pituitary problem.
-Serum TSH low and T3/T4 are elevated, this is indicative of
hyperthyroidism.
COMMON LABORATORY TESTS
Lipid Panel
A lipid panel is comprised of:
Cholesterol- Total cholesterol
Triglycerides- Fat in the blood from meals or made by liver in response to sugars and
fats. This can be elevated if the patient ate a high fat meal before the blood draw.
HDL (High density lipoprotein)- the “good” cholesterol, removes excess cholesterol
and moves it to the liver
LDL (Low density lipoprotein)- The “bad” cholesterol, deposits excess cholesterol in
the walls of blood vessels
Non HDL- Total cholesterol minus the HDL
Chol/HDL Ratio – Total cholesterol divided by HDL.
REFERENCES
Up to Date (2016). Lab results retrieved from uptodate.com
Accessed February 20th, 2016.
The Mayo Clinic (2016). Diseases and Conditions retrieved from
themayoclinic.org accessed February 20th, 2016