Interpreting Clinical Lab Data
M.ABD ELAZIZ, PhD, MD
Professor of clincal pharmacology
Mansoura University
GENERAL PRINCIPLES
Generally, laboratory tests should be ordered only
1-if the results of the test will affect decisions about
the care of the patient.
2- The serum, urine, and other bodily fluids can be
analyzed routinely;
3-however, the economic cost of obtaining these data
must always be balanced by benefits to patient
outcomes.
Normal Values
 Clinical laboratory test results that appear within a predetermined
 range of values are referred to as “normal,” and those outside this range are typically





referred to as “abnormal.”
Laboratory findings, both normal and abnormal, can be helpful in Assessing:
clinical disorders, establishing a diagnosis, assessing drug therapy, or evaluating
disease progression
. In addition, baseline laboratory tests are often necessary to evaluate disease
progression and response to therapy or to monitor the development of toxicities
associated with therapy.
Clinical laboratories can analyze sample specimens by different laboratory methods;
therefore, each laboratory has its own set of normal values. Consequently, clinicians
should rely on normal values listed by their own clinical laboratory facility when
interpreting laboratory tests.
Laboratory Error
 Avariety of factors can interfere with the accuracy of laboratorytests.
 1- Patient-related factors (e.g., age, gender, weight,height, time since last meal) can affect the range of
normal values
 for a given test.
 2- Laboratory-based issues can also influence the accuracy of laboratory values.












For example, a specimencan be spoiled
A-because of improper handling or processing (e.g., hyperkalemia due to hydrolysis of a blood
specimen);
B-because it was taken at a wrong time (e.g., fasting blood glucoselevel taken shortly after a meal);
C- because collection was incomplete (e.g., 24-hour urine collection that does not span a full 24-hour
period);
3- Errors also can arise due to faulty poor quality reagents (e.g., improperly prepared, outdated);
4-due to technical errors (e.g., human error in reading result, computer-keying error);
5- due to interference from medical procedures (e.g., cardioconversion increases creatine kinase [CK]
serum concentrations);
6-due to dietary effects (e.g., rare meat ingestion can cause a false-positive guaiac test);
7- because medications can interfere either with the testing procedure or by their pharmacologic effects
(e.g., thiazides can increase the serum uric acid concentration, β-agonists can reduce serum potassium
concentrations).
8-Clinicians might not be aware of when laboratory-related issues arise.
As a result, laboratory findings must always be interpreted carefully, and the validity of a test result
questioned when it does not seem to correlate with a patient’s clinical status.
Side A
Side B
Side A
Side B
1
aden/o
.
gland
11.carcin/o
cancer
2
cardi/o
.
heart
12.chem/o
chemical
3
cis/o
.
to cut
13.dermat/o
skin
4
enter/o
.
small intestines
14.gastr/o
stomach
5
gynec/o
.
female
15.hemat/o
blood
6
hydr/o
.
water
16.immun/o
immun
7
laryng/o
.
voice box
17.morph/o
shape
8
nephr/o
.
kidney
18.neur/o
nerve
9
ophthalm/o
.
eye
19.ot/o
ear
1
0path/o
.
disease
20.pulmon/o
lung
Interpreting Clinical Lab Data
Objectives:
1. Identify the characteristics and function of each
type of leukocyte.
2. Identify the significance of comparing the WBC
count to the neutrophil count in patients with
pneumonia.
3. Identify common causes for increases and
decreases in the neutrophil count.
4. State how the “rule of three” is useful for
interpretation of the RBC count and indices.
Divisions of the Clinical Lab
 Hematology
– Complete blood count
• WBC count
• Platelets
• RBC count
 Chemistry
– Electrolytes
•
•
•
•
Potassium
Sodium
Total CO2
Chloride
Divisions of the Clinical Lab
Microbiology
– Sputum gram stain
– Sputum culture and sensitivity
– Pleural fluid culture and sensitivity
Blood Bank
- blood typing and storage
CELL MORPHOLOGY
Cell Morhphology (neutrophil)
 Segmented neutrophil
(40-70% of WBCs)
 Life span of about 10
days
 Moves from bone marrow
to blood to tissues
 Mature more quickly
under stressful conditions
 Primary defense for
bacterial infections
Cell Morhphology (neutrophil)
The Neutrophil
Once in the peripheral blood, it can be in
the circulating pool (CP) or the marginated
pool (MP) (approx. 50%)
cells in MP not counted in CBC
Shift from the MP to the CP can occur with
stress, trauma, catecholamines, etc.
This results in a transient leukocytosis
Such leukocytosis can last 4 to 6 hours
The Neutrophil
Present in band and segmented forms
Bands make up < 5 % of circulating
neutrophils normally
“Left shift” is seen as an increase in the
number of bands and is common with
acute infection
Main function is to locate, ingest, and kill
bacteria and other foreign invaders
Cause of Neutrophilia
 Pathologic
– Bacterial infection
– Certain viruses and fungi
– Inflammatory responses to tissue death
• Burns
• Snake bites
 Drugs
– steroids
– lithium
Causes of Neutrophilia (cont.)
Physiologic
– Pseudoneutrophilia (shift of cells from the MP
to CP)
• Catecholamines
• Acute stress
Other inflammatory responses
– Neoplastic growth
– Metabolic disorders
Pools of Neutrophils
1. Bone marrow: many banded forms are
present; neutrophilia with lots of bands
suggest bone marrow was source
2. Circulating Pool: used to deal with day to
day invasion of the body by organisms
3. Marginated Pool: no bands; respond to
physiologic stimulation
Causes of Neutropenia
 Decreased Production of WBCs
– bone marrow diseases
– malignancies that affect the bone marrow
 Increased Neutrophil Destruction
– overwhelming infection
– certain bacteria
– immune reactions
 Pseudoneutropenia (shift of cells from CP to MP)
– viral infections
– hypothermia
Cell morphology (Eosinophil)
 Segmented eosinophil
 Life span = 14 days
 Spends little time in the
blood before it locates in
the skin, GI tract, or
respiratory tract
 Only 1% of mature cells
are located in blood
The Eosinophil
Also function as phagocytes but appear to
be less potent than neutrophil
Drawn to sites of hypersensitivity reactions
by mast cell chemotactic factors
Often found in sputum of asthmatics
May play a role in pathogenesis of lung dz
Play a role in parasitic infections
The Basophils
 Mature basophil
 Least common of
WBCs (< 2%)
 Nucleus does not
always segment
 Increase in response
to same conditions
that cause eosinophils
to respond
The Monocytes
 Also not common in
circulating blood
 Stay in blood for
about 70 hours
 Become macrophages
in tissue and live for
several months or
longer
The Monocytes
Primary role is phagocytosis
Play large role in ingesting cellular debris
Become “activated” when direct contact
with microorganisms occurs
Activated cell has greater motility, enzyme
activity and killing capacity (causes fever)
Also play a role in immunity
The Lymphocytes
 May mature into B or T
cells
 Main function is
antigen recognition and
immune response
 Life span quite varied
(up to two years)
 Can pass back and forth
between blood and
tissues
Lymphocytes: B & T types
B cells are not only produced in the bone
marrow but also mature there.
However, the precursors of T cells leave
the bone marrow and mature in the thymus
(which accounts for their designation)
Types of Lymphocytes
 B lymphocytes (or B cells) are most effective
against bacteria & their toxins plus a few viruses
 T lymphocytes (or T cells) recognize & destroy
body cells gone awry, including virus-infected
cells & cancer cells.
 T cells come in two types: helper cells and
suppressor cells; normally the helper cells
predominate.
Lymphocyte Count: Decreased
I.
A.
B.
C.
D.
E.
1.
2.
3.
Decreased
AIDS
Bone Marrow suppression
Aplastic Anemia
Steroids
Neurologic Disorders
Multiple Sclerosis
Myasthenia Gravis
Gullain Barre Syndrome
Lymphocyte count: Increased
a. Influenza
b. Pertussis
c.
d.
e.
f.
g.
h.
Tuberculosis
Mumps
Cytomegalovirus Infection
Infectious Mononucleosis
Infectious Hepatitis
Viral pneumonia
Interpreting the CBC
What is total white cell count?
If elevated (>11,000), what type of WBC is
the culprit?
Is it the neutrophils, eosinophils,
lymphocytes, basophils, or monocytes?
Marked leukocytosis is usually due to
neutrophils or lymphocytes.
Interpreting the CBC
Normal
Values
Neutrophils
%
Absolute
40 – 70
1800 – 7500
Eosinophils
0–6
0 – 600
Basophils
0–1
0 – 100
20 – 45
900 – 4500
2–6
90 - 1000
Lymphocytes
Monocytes
Interpreting the CBC
If the neutrophils are causing the
leukocytosis, compare the neutrophil % to
total WBC.
The % neutrophils indicates the severity of
the infection; the total WBC reflects the
quality of the immune system
Interpreting the CBC (Case # 1)
85 yr old female with pneumonia:
Total WBC is: 11,500
Neutrophil % = 80% (9200) bands = 5%
This indicates that a severe infection is
present but the immune system is unable to
respond appropriately.
Prognosis poor.
Interpreting the CBC (Case # 2)
5 yr old male with pneumonia
WBC = 18,000
Neutrophils = 60% (10,800)
Marked leukocytosis and normal range for
neutrophils indicates moderate infection
but excellent immune system response
Excellent prognosis
Interpreting the CBC (Case #3)
10 yr old male admitted for pneumonia:
WBC: 16,000
neutrophils = 75%
(12,000)
(1800-7500)
Bands =
5%
(800)
(0-100)
Eosinophils = 1%
(160)
(0-600)
Lymphocytes = 10%
(1600)
(900-4500)
Basophils = 0%
(0)
(0-100)
Monocytes = 3%
(480)
(90-1000)
Interpreting the CBC (Case #3)
Interpretation
neutrophilia probably due to bacterial
pneumonia
left shift indicative of severe infection
the source of the neutrophils is the bone
marrow since many bands are present
Case Study # 4
20 yr old male admitted following MVA
WBC 14,500 75% neutrophils 1% bands
Leukocytosis due to neutrophilia
History and low per cent of bands suggest
pseudoneutrophilia
Due to liberation of marginated neutrophils
in the intravascular system
Interpreting the CBC
What is indicated by leukopenia?
1. Bone marrow failure
cancer e.g. leukemia, lymphoma
2. Overwhelming infection
severe pneumonia pt who has poor immune
system and can’t produce enough WBCs
3. Shift of neutrophils to MNP (viral infections
and hypothermia)
Platelet Count
Normal count is 140,000 to 440,000/mm3
Life span of about 10 days
Low platelet counts (thrombocytopenia)
cause excessive bleeding
Thrombycytopenia is common with the use
of heparin, DIC, bone marrow disease,
liver failure and sepsis
Platelet
Platelet (Activated)
Side A
1
aden/o
.
2
cardi/o
.
3
cis/o
.
4
enter/o
.
5
gynec/o
.
6
hydr/o
.
7
laryng/o
.
8
nephr/o
.
9
ophthalm/o
.
1
0path/o
.
Side B
Side A
Side B
gland
11.carcin/o
cancer
heart
12.chem/o
chemical
to cut
13.dermat/o
skin
small intestines
14.gastr/o
stomach
female
15.hemat/o
blood
water
16.immun/o
immun
voice box
17.morph/o
shape
kidney
18.neur/o
nerve
eye
19.ot/o
ear
disease
20.pulmon/o
lung
22.a ,
without,
away from
27.an
without
23.ante
before, in
front of
28. anti-
, against
24.auto
, self
29. brady
slow
25.dys-
painful,
difficult
30. endo
, within,
inner
Red Blood Cells
Red Blood Cells (Erythrocytes)
 Produced in the bone
marrow
 Life span of about
120 days
 Primary function is
gas transport
 Immature version has
nucleus and is called a
reticulocyte
Interpreting the RBC count
1. Normal values:
Men: 4.2 – 5.4 million/mm3
Women: 3.6 – 5.0 million/mm3
2. Anemia –
abnormal Decrease in RBC count
- decreased production
- increased destruction (hemolysis)
- blood loss
Interpreting the RBC count
3. Increased RBC count = Polycythemia
A. Primary
B. Secondary
living at altitude
chronic lung/heart disease
tobacco use/carbon monoxide
C. Relative Polycythemia
dehydration
Red Blood Cell Indices
 Mean Corpuscular Volume (MCV)
– Volume occupied by a single RBC
– Increase in MCV is known as Macrocytic anemia.
– Decrease in MCV is known as Microcytic anemia.
 Mean Corpuscular Hemoglobin Concentration
– (MCHC)
– Measure of the concentration of hemoglobin in an
average RBC
– Decrease in MCHC is known as Hypochromic anemia
– Normal is known as Normochromic anemia.
Red Blood Cell Indices
 Normocytic anemias
– Blood loss
– Hemolytic anemia
 Microcytic anemias (<80 fL*)
– Iron deficiency
 Macrocytic anemias (>100 fL)
– Folic acid deficiency
– Vitamin B12 deficiency
– Some COPD patients
*femtoliters
Red Blood Cell Indices
Hematocrit
The RULE of Three
Applies to normocytic, normochromic
erythrocytes only
Useful to detect laboratory error in
measuring the Hb, HCT, and RBC count
3 times the RBC count should = Hb
3 times Hb should = Hct
The RULE of Three
RBC = 3.0 x 1012
3x3=9
Hb = 9.2 g/dL
3 x 9.2 = 27.6
Hct = 28%
Interpreting the Red Blood Cells
CBC:
RBC (x1012/L)
Hgb (g/dL)
Hct
MCV (m3)
MCHC
Results
4.2
10.6
34.9%
77.0
30.4%




Normals
4.2-5.4
11.5-15.5
38%-47%
80-96
32-36%
Interpretation: Microcytic, hypochromic anemia; rule of 3
does not apply
Reticulocyte Count
 Normal values:
– 0.5 – 1.5% of RBC
 Helpful to identify cause
of Anemia
 Increase indicates
Anemia is due to Blood
loss
 Decrease indicates
Anemia is due to Bone
marrow disease
Bibliography
Steine-Martin: Clinical Hematology, 2nd
edition, Lippincott, Philadelphia, 1998.
Kaplan: Clinical Chemistry, 4th edition,
Mosby, St. Louis, 2003.
Wilkins: Clinical Assessment in
Respiratory Care, 5th edition, Mosby, St.
Louis, 2005.