Interpreting Clinical and
Laboratory Data
Wilkins Chapter 7
Egan Chapter 16
Des Jardins Chapter 8
Clinical Laboratory Tests
• Evaluates Patients:
• Health status
• Identify organ-system dysfunction
• Detect presence of infection
• Effects of therapy
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Intro to Laboratory Medicine
• Divided into 5 major disciplines:
• Clinical Biochemistry – analysis of
blood, urine & bodily fluids
• Hematology – analyzes cellular
components of blood
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Laboratory Medicine
• Microbiology – analysis of blood/sputum
& other bodily fluids for presence of
infectious agents
• Immunology – focuses on autoimmune
& immune deficiency diseases
• Anatomic Pathology – analysis of tissue
for diagnosing disease
Reference Range
• Takes into account variations related to:
• Age
• Gender
• Race
• Ethnicity
• Vary slightly from laboratory to laboratory
• Referred to as “normal range
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Critical Test Value
• Result significantly outside reference range
• Represents pathophysiologic condition
• May represent potentially life threatening
situation
• Documented reporting required – person
to person
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The normal or expected boundaries for any
analysis such as electrolytes, blood cells, proteins,
or enzymes that would likely be encountered in
healthy subjects is called a:
A. Reference range
B. Critical value
C. Range level
D. Normal value
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Complete Blood Count (CBC)
• Common test measuring formed elements
of blood
• Counts & examines:
• Leukocytes (white blood cells)
• Erythrocytes (red blood cells)
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• Thrombocytes (platelets)
Complete Blood Count (CBC)
(cont.)
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___________are evaluated for size and
hemoglobin content.
A. White blood cells
B. Red blood cells
C. Platelets
D. Proteins
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White Blood Cell Count
• WBC count above normal is
called_______________________
• Leukocytosis - common with infection, stress,
& trauma.
• Degree of leukocytosis depends on severity of
infection
• Severe infection with mild leukocytosis may
represent poor prognosis
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White Blood Cell Count
• Below normal
represents:________________________
• Occurs with overwhelming infections &
when immune system is depressed due
to disease or certain cancer therapies
(chemotherapy)
• Diseases of bone marrow (e.g.,
leukemia) can cause leukopenia
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Differential of WBC Count
• Leukocytosis is most often due to elevation of
only 1 of 5 types of white blood cells
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Rule of Thumb
• Elevation of the WBC count is usually caused by
an increase in either neutrophils or lymphocytes
in response to infection.
Rule of Thumb
• When bacterial pneumonia is present, the
severity of the infection can be assessed by
evaluation of the degree of increase in
neutrophils.
Left Shift
• Bone marrow is stimulated to release
neutrophils at a fast rate to respond to infection.
• Large numbers of immature cells, called bands,
are produced.
• This is called a left shift
Mini Clini: White Blood Cell
Count Differential
• Problem
• A patient has been admitted to the hospital for
acute shortness of breath. A chest x-ray
reveals pneumonia, and the patient's
temperature is elevated. The CBC shows an
increased WBC count of 15 × 103/mcl with 75%
neutrophils but only 10% lymphocytes. Given
that the normal lymphocyte differential is 20%
to 45%, does the value of 10% suggest a
problem with lymphocyte production by the
immune system? What type of pneumonia is
probably present in this case?
Mini Clini: White Blood Cell
Count Differential
• Solution
• The 10% differential for the lymphocytes
represents a relative value. Because the total WBC
count is markedly elevated, the 10% in relative
terms represents 1500 lymphocytes in absolute
value, which is well within normal range. If the
total WBC count was reduced to less than normal
and the differential showed a lymphocyte count of
10%, an abnormal absolute value would be
present and would suggest an immunologic
problem. This patient probably has bacterial
pneumonia, given the elevated number of
neutrophils.
Differential of WBC Count (cont.)
• Neutrophilia: Elevation of absolute value of
neutrophils
• Bands: Immature neutrophils
• Segmented neutrophils (segs): mature
neutrophils
• When bands & segs are elevated in CBC, patient
is likely experiencing more severe bacterial
infection
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A significant elevation of the WBC count (more
than 15 x 103/mcl) will occur only when either
neutrophils or __________ are responding to an
abnormality.
A. Basophils
B. Eosinophils
C. Monocytes
D. Lymphocytes
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Red Blood Cell Count
• Reduced RBC count is called anemia
• Anemia is due to either blood loss or
reduced RBC production by bone
marrow
• Anemia reduces oxygen-carrying
capacity of blood
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Anemia
• Several types of anemia exist with
different causes (dietary deficiencies,
chronic inflammatory disease, hereditary)
• Severe anemia is treated with transfusion
• See text for types and causes of anemai
Red Blood Cell Count
• Abnormal elevation of RBC count is known as
polycythemia
• Secondary polycythemia occurs when bone
marrow is stimulated to produce more RBCs in
response to chronically low blood oxygen levels
• Common in people who live at an elevated
altitude & in patients with chronic hypoxemic
lung disease
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Red Blood Cell Count
• Includes hemoglobin & hematocrit levels
• Hemoglobin (Hb)
• Plays role of bonding with oxygen
• Normal hemoglobin concentration is 12-17
g/dL
• RBCs with reduced hemoglobin are smaller
than normal (microcytic anemia) & lack normal
color (hypochromic anemia).
• An RBC transfusion depends on cause of anemia
& patient’s overall condition
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Red Blood Cell Count
• Hematocrit Levels
• Ratio of RBC volume to that of whole blood
• Proportion of sample represented by packed
cells
• Low levels occur with anemia or overhydration
• High levels occur with polycythemia &
dehydration
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Rule of Thumb
• The threshold for blood transfusion typically is a
hematocrit of 21% or a hemoglobin of 7.0 g/dl.
A patient’s results on a blood test shows that her
hematocrit percentage is approximately 20%.
What should the clinician recommend for this
patient?
A. nothing, patient’s result is normal
B. patient should receive a blood transfusion
C. repeat test due to erroneous result.
D. patient should undergo plasmaphoresis
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Electrolyte Test
• Normal cellular function depends upon
homeostasis of fluid, electrolytes & acid-base
balance
• Electrolytes are charged ions influencing
functioning of enzymes
• Enzymes are proteins regulating all chemical
reactions occurring within cells (metabolism,
protein synthesis)
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Electrolyte Tests (cont.)
1. Series of blood samples provides insight of
severity & progression of disease &
effectiveness of therapy
2. Intravascular blood compartment
(extracellular environment) is separate from
intracellular environment. Thus, blood
samples provide important, but indirect
information of intracellular electrolytes
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The ability of a complex organisms to maintain a
dynamic balance or equilibrium in their internal
environment by making constant adjustments is
called
A. homeostasis
B. electrolytes
C. cellular function
D. polycythemia
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Electrolyte Tests – Blood
Chemistry
• Predominant electrolytes measured in lab:
• Sodium (Na+)
• Potassium (K+)
• Chloride (Cl-)
• Total CO2 / bicarbonate (bicarb)
• Glucose (GL)
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Blood Chemistry
• Excretion of renal-mediated waste
products is included in panel :
Creatine (Cr) & blood urea nitrogen
(BUN).
• More comprehensive metabolic panel
would include: Magnesium,
Phosphorus, Calcium
Electrolyte Tests - Glucose
• Formed from breakdown of carbohydrates
• Metabolized by cells for energy
• Requires insulin to be utilized by cells
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Blood Glucose
• Hyperglycemia
• Elevation of blood glucose
• Often result of diabetes
Electrolyte Tests - Glucose
• Hypoglycemia
• Reduced glucose level
• May result from inadequate diet or
drug induced/ insulin overdose
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Diabetes
• Diabetes
• Diagnosed by fasting blood glucose levels
• Indicated by 140 mg/dL on two occasions
• Severe hyperglycemia occurring with metabolic
acidosis is consistent with diabetic ketoacidosis
Electrolyte Tests – Anion Gap
• Metabolic acidosis is caused by addition
of non-volatile acids or loss of HCO3• Determines if decrease in HCO3- is
caused by disruption of normal anion
balance or presence of abnormal acid
anion
• Normal level is 8-14 mmol/L
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Mini Clini: Anion Gap
• Problem 1
• A patient in the intensive care unit is being
treated for shock and acute renal failure. No
ABGs have been drawn yet, but the RT suspects
the respiratory system is involved because the
patient has been breathing more rapidly over the
past 12 hours. The electrolyte panel reveals a
serum Na+ of 146 meq/L, a total CO2 of
20 meq/L, and a serum Cl− of 100 meq/L. Does
the electrolyte panel suggest any problems, and
what should be done if there are any?
Mini Clini: Anion Gap
• Solution
• The electrolytes are normal except for a
decrease in the serum CO2. The anion gap is
calculated by subtracting the sum of CO2 and Cl−
from the Na+ (146 − [100 + 20]). In this case, the
anion gap is elevated (26 meq/L) and is
consistent with a metabolic acidosis. An ABG
analysis is needed to evaluate the acid-base
status of the patient further. The patient's rapid
breathing probably is related to the metabolic
acidosis because hyperventilation decreases CO2
levels and promotes acid-base compensation.
Mini Clini: Anion Gap
• Problem 2
• A patient in the trauma intensive care unit is
undergoing large fluid resuscitation with normal
saline solution. The patient is in hemorrhagic and
hypovolemic shock following a motor vehicle
accident. An initial ABG reveals a pH of 7.25, PCO2 of
25 mm Hg, and HCO3− of 10.6 with a base deficit of
−14.9 meq/L. The trauma surgeons are debating
increasing the amount of normal saline solution
infused. They suspect their resuscitation efforts are
inadequate, and metabolic acidosis is worsening
from continued lactate accumulation. What
additional information can be provided by obtaining
a BCP to help guide therapy?
Mini Clini: Anion Gap
• Solution
• If the BCP reveals a Na+ of 140 meq/L, Cl− of 95 meq/L,
and CO2 of 20 meq/L (anion gap of 25 meq/L), the
surgeons would be correct in assuming that their
resuscitation efforts were inadequate. The anion gap of
25 likely represents a worsening lactic acidosis. However,
if the BCP reveals a Na+ of 150 meq/L, CO2 of 20 meq/L,
and Cl− of 122 meq/L, the anion gap would be normal
(8 meq/L). The metabolic acidosis would be caused by an
abnormally high serum chloride concentration from
excessive normal saline administration. This example
represents a common problem in emergency and critical
care practice: the overresuscitation of trauma patients
from severe shock.
Rule of Thumb
• An anion gap greater than 16 is
consistent with the presence of
metabolic acidosis.
Electrolyte Tests- Lactate
• End product of anaerobic glucose metabolism
• Overproduction or insufficient metabolism
results in lactate acidosis
• Abnormal levels can be found in anaerobic
metabolism, diabetes mellitus & malignancies
• Initial values of serum lactate > 4 mmol/L are
associated with higher mortality in patients
with septic shock
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Rule of Thumb
• In patients with septic shock, a serum
lactate level greater than 4 meq/L is
associated with higher mortality.
• What is septic shock?
A medical resident asks for your advice in assessing
renal function in a critically ill patient. You would
suggest to test for all of the following:
1. glucose (GL)
2. BUN
3. Creatinine
4. Sodium (Na+)
A.1, 2 and 3only
B.2 and 3 only
C.1 and 4only
D.1, 2, 3 and 4
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Electrolyte Disorders
• Severe levels have profound impact on
pulmonary function
• Causes skeletal muscle weakness that may limit
ambulation - may lead to development of
pneumonia
• Causes respiratory muscle weakness impairing
ability to sustain spontaneous ventilation &
maintain pulmonary hygiene
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Liver Function Tests - LFTs
• Liver damage is assessed by abnormal
increases in hepatic enzymes
• Total bilirubin (TBIL) – crucial component of
liver panel
• Total protein (TP) & albumin (ALB) used to
asses protein synthesis
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Cardiac Enzymes
• Most common CPK enzyme test is for CPK-2
which is released from heart following MI
• Normal ranges vary, check your lab
•
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Troponin
• Troponin-I (protein fragment) levels peak 1216 hours after MI
• Normal troponin levels are 10 or less
micrograms per liter of troponin I and 0 to 0.1
micrograms per liter of troponin T. Higher
levels of these complex proteins results in
heart attack and respiratory problems.
Troponin regulates the contraction and
relaxation of skeletal and cardiac muscles.
Protein Markers
• B-Type Natriuretic Peptide (BNP) is used to
evaluate patients for heart failure in patients
with dyspnea and pulmonary edema
BNP
• BNP
• > 300 pg/ml indicates mild heart failure
• > 600 pg/ml indicates moderate heart failure
• > 900 pg/ml indicates severe heart failure.
Pancreatic Enzymes
• Pancreatic & Muscle Enzyme Tests
• Pancreatitis will have abnormal
levels of pancreatic enzymes lipase
& amylase
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Muslce Enzyme Tests
• Suffering ischemic damage to the heart,
brain, & skeletal muscle tissue will have
elevated creatine phosphokinase (CPK)
• Increased levels of lactate
dehydrogenase (LD) is associated with
tissue breakdown
A 67-year old female is assessed with abnormal
increases in the enzymes alanine
aminotransferase (ALT), aspartate
aminotransferase (AST), as well as alkaline
phosphatase (ALK). What does this indicate?
A. respiratory problem.
B. kidney damage.
C. pancreas disorder.
D. liver damage.
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Coagulation Studies
• Thrombocytopenia (low platelets) &
thrombasthenia (abnormal platelet
functioning) leads to excessive
bleeding
• Thrombocytosis (excessive platelets)
causes excessive clotting
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Coagulation Studies
• Prothrombin Time (PT)
• Partial Thromboplastin Time (PTT)
• PT is accompanied by an additional
measurement - International Standardized Ratio
(INR)
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Enzyme Tests (cont.)
• Coagulation Studies
• D-Dimer
• Found in blood when fibrin clots are dissolving
• Help diagnose the presence of deep vein
thrombosis, pulmonary embolism or
disseminated intravascular coagulation (DIC)
• Protein C
• Regulates coagulation
• Active state (Activated Protein C (APC)) inhibits
coagulation & promotes degradation of clots
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Coagulation Disorders
• Must check patient’s clotting levels prior to
performing an arterial blood gas (ABG) or
nasotracheal suctioning
• Abnormally low platelet count or an elevated PT
and INR will need an ABG puncture site
compressed for longer time to prevent bleeding
& hematoma
• Extremely low platelet count should have an
ABG or nasotracheal suctioning done only when
necessary
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Sweat Chloride
• Cystic Fibrosis (CF)
• CF patient’s have elevated level of sweat Cl• 40-60 mmol/L is borderline
• <40 mmol/L are unlikely to be diagnosed
• Must be accompanied by other tests to
confirm diagnosis
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Microbiology
• Sputum Gram Stain
• Suspected infection in lungs or airways may
benefit from analysis of sputum sample
• Legitimate sputum sample will have numerous
pus cells & few epithelial cells
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Gram Stain
• Gram stain can determine if offending
organism is gram positive or gram negative &
its shape
• Culture can identify specific organism
• Determine organisms sensitivity to antibiotic
therapy
Rule of Thumb
• A legitimate sputum sample has few epithelial
cells and many pus cells (leukocytes).
Microbiology
• Acid-Fast Testing
• Identifies acid-fast bacterium
• Steps:
• Gram stain sputum sample
• Acid wash sputum sample
• If organism is resistant to decolorization, then
it is classified as an acid-fast bacterium
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