The CBC:
More Information
Than You Thought
JoAnn Deasy, PA-C. MPH
San Francisco, CA
jadeasy@sbcglobal.net
Adjunct Lecturer Touro PA Program
California Emergency Physicians Group
Complete Blood Cell Count (CBC)
Information
• RBC, WBC & Platelets
• Correct interpretation
requires knowledge of
the clinical significance
of results as well as
knowledge of the
instruments producing
the results
Learning Objectives
• Recognize information that can be gleaned
from the electronic complete blood cell count
(CBC) regarding red blood cells, white blood
cells and platelets
• Discuss how findings on the peripheral smear
complement the electronic CBC
• Correlate findings on the CBC to disease
states
Electronic Counters
• Virtually all laboratories now use automated
hematology instruments to generate the CBC
• The Coulter Counter (Beckman) introduced
automation in 1968
– 1977 platelets
– 1983 leukocyte differential
• Continued innovation in electronic hematology
counters generating more reportable
parameters
1
Electronic Counter
Analytic Parameters
• Excellent performance
– WBC and RBC count
– Hemoglobin concentration
– Mean corpuscular volume (MCV)
• Less satisfactory
– Certain componets of the leukocyte differential count (LDC)
– Platelet count at low concentrations
• Caution
Ordering a CBC
• To diagnose anemia
• To support a diagnosis of infection
• To identify white blood cell disorders such as
leukemia
• To identify bleeding tendencies from low platelets
• To determine the effects of chemotherapy and
radiation therapy on blood cell production
– Red cell distribution width (RDW) and mean platelet volume
affected by time from blood draw to analysis
2
RED BLOOD CELL
INFORMATION
Red Blood Cell Information
• Total RBC count
• Hemoglobin / Hematocrit
• RBC indices
– Mean Corpuscular Volume (MCV)
– Mean Corpuscular Hemoglobin (MCH)
– Mean Corpuscular Hemoglobin Concentration
(MCHC)
– Red Cell Distribution Width (RDW)
• Manual examination of peripheral smear
RED BLOOD CELL COUNT
• Number of RBC per µL
– 4.5 to 6 million
• Gender dependent
– Interpret in conjunction with hemoglobin,
hematocrit and rbc indices
• Regulation by erythropoetin in kidney
– Stimulus to produce erythropoetin include
hypoxia, anemia, high altitude
Red Blood Cell count
• Causes of decrease
– Anemia
• Special situation of thalassemia minor
– Excessive IV fluids
• Causes of increase
– Dehydration
– Polycythemia vera
– Secondary polycythemia
3
HEMOGLOBIN and HEMATOCRIT
• Hemoglobin (Hgb): Oxygen carrying pigment of
the rbc and best measure of the oxygen carrying
capacity of the rbc.
– Measured in grams per 100 ml
Rule of Threes
• Checks for artifacts
– Hct = 3X hgb
Hgb 10.7 g/dL
– Hgb = 3X rbc count
Hct
17.8%
• Hematocrit (Hct): Measures packed RBC volume
– expressed as % per fluid volume of whole blood
MEAN CORPUSCULAR
VOLUME (MCV)
RBC Indices
• Very accurate
• Measurement of the size of the cell
– 80-100 fL = normocytic cells
– <80 fL
= microcytic cells
– >100 fL = macrocytic cells
4
MEAN CORPUSCULAR
HEMOGLOBIN (MCH)
• Measure of the average amount of hgb in an
individual rbc
– Reference range: 27-34 pg
• Does not take into account the size of the rbc
• Usefulness?
– Small cells have less hemoglobin, large cells more,
so variation in MCH tracks along with MCV. Adds
little information independent of the MCV
MCHC
• Low MCHC = hypochromic
• Normal MCHC = normochromic
• High MCHC = hyperchromic
MEAN CORPUSCULAR HGB
CONCENTRATION (MCHC)
• Relative value, average concentration of hgb in
a red blood cell
– Expressed as %, reference range 32-36%
• or as g/dl of red cells (34 +/- 2 g/dl)
• Very few conditions cause elevated MCHC
– Spherocytosis
– Cold agglutinin
• Decreased MCHC
– Iron deficiency, anemia of chronic disease, sideroblastic
anemia
RDW
Red Cell Distribution Width
• Indicates cell size variability - anisocytosis
• Reference range: 11-14.5%
• Elevated RDW:
– Considerable variation in size of cells
• RDW may be useful in separating IDA and
thalassemia minor
– Limited by wide distribution of RDW values within
a given disease
5
EXAMINATION of
PERIPHERAL SMEAR
Peripheral Smear
Examination of RBCs
• Complements rbc indices and RDW
• Size
• Morphology
– Shape and staining characteristics
USING CBC to EVALUATE
ANEMIA
1. Check hemoglobin/hematocrit
–
–
14-18 gms/100 ml men
12-16 gms/100 ml women
DIFFERENTIAL DIAGNOSIS of
MICROCYTIC ANEMIA
• Iron deficiency anemia
• Thalassemia
• Anemia of chronic disease
2. Check MCV and classify anemia
–
–
–
Microcytic
Normocytic
Macrocytic
• Sideroblastic anemias
• Lead poisoning
• Copper deficiency
6
Microcytic and Normocytic
Anemias
NORMOCYTIC ANEMIAS
• Anemia of Chronic Disease
• Hemolytic Anemia (or macrocytic)
• Spherocytosis
• Microcytic and normocytic anemias next step
is to order iron studies
MACROCYTIC ANEMIAS
MCV > 100
Lab Findings in Microcytic Anemias
Test
MCV
RDW
Ferritin
Iron
TIBC
% Sat
Iron Def Thalassemia
Low
High
Low
Low
Inc
Low
Low
Normal
Nl or Inc
Normal
Normal
Normal
Chronic
Low or nl
Normal
Nl or Inc
Low
Low or nl
Nl or low
•
•
•
•
•
•
•
•
Alcohol Abuse and liver disease
Vitamin B 12 Deficiency
Folic Acid Deficiency
Hemolytic Anemia
Drug effects
Hypothyroidism
Myelodysplasia
Idiopathic refractory sideroblastic anemia
7
Tests
16 year old Latin American girl comes to the
office with her mother because mom thinks
her daughter acts tired. Daughter says she
feels fine. ROS is negative except for poor
dietary habits (mostly fast food) and for
history of heavy menses. Menses lasts 7
days. Menarch age 10. She has never had a
pelvic examination. She is a junior in high
school and says school is “boring” but she
gets “okay” grades.
Iron Studies
Iron
TIBC
Ferritin
12
487
0
50-175
250-460
11-122
µg/dL
µg/dL
ng/mL
WBC
RBC
Hgb
Hct
MCV
MCH
MCHC
RDW
Result
6.2
3.38
5.8
19.2
68
17.2
28.8
17.9
Reference Range
4.0-10.8
F 4.2-5.4
F 12-16
F 37-47
80-99
27-31
33-37
11.5-14.5
x103
x106
g/dL
%
fl
pg
%
%
3+ microcytosis, 2+ anisocytosis,
3+ poikilocytosis, 3+ hypochromasia
36 year old Filipino woman comes to the office
for a routine physical examination. Her past
medical history includes mild anemia, that
was never specifically diagnosed and was not
treated. She reports having heavy menses.
Her physical examination is unremarkable.
8
WBC
RBC
Hgb
Hct
MCV
MCH
MCHC
RDW
4.9
6.21
10.7
34.8
56
17.2
30.6
14.3
4.8-10.8
F 4.2-5.4
F 12-16
F 37-47
80-99
27-31
33-37
11.5-14.5
x103
x106
g/dL
%
fl
pg
%
%
3+microcytosis, 3+ hypochromasia
moderate # target cells
Further Studies
Iron
TIBC
Ferritin
94
387
90
50-175
250-460
11-122
µg/dL
µg/dL
ng/mL
Hemoglobin Electrophoresis
Hgb A
89.5
95.8-98.5%
Hgb F
2.8
0.0-2.0%
Hgb A2
7.7
1.8-4.2
23 year old man with vague symptoms
WBC
RBC
Hgb
Hct
MCV
MCH
MCHC
RDW
3.8
3.91
10.7
32.7
84
27.3
33
13.5
4.0-10.8
M 4.7-6.1
M 14-18
M 42-52
80-99
27-31
33-37
11.5-14.5
x103
x106
g/dL
%
fl
pg
%
%
Iron
TIBC
Ferritin
22
230
300
50-175
250-460
11-122
µg/dL
µg/dL
ng/mL
9
TOTAL WBC COUNT
• Leukocytosis = >11,000 WBC per / µL
– Myeloproliferative disorders
– Infection (especially bacterial)
White Blood Cell Information
from the CBC
• Absent in 15-30% of cases
– Tissue necrosis
• Leukopenia = < 4,500 / µL
Total WBC Count (4,500-11,000 / µl)
Leukocyte (WBC) Differential – Relative and Absolute
– Viral infection usually leukopenia or normal wbc
– Drugs
• Examples: clozaril, chemotherapeutic agents
– Autoimmune disease
– Aplastic anemia
Automated
Leukocyte Differential Count (LDC)
• Movement to report only absolute values
• Monocyte and basophil counts less reliable
• Does not count bands or other immature
granulocytes
• When LDC abnormal and/or flags an eyecount
differential should be performed
– Diagnosis of certain infections
– Leukemia
– Anemia
ABSOLUTE DIFFERENTIAL
•
•
•
•
•
•
WBC
PMNS
LYMPHOCYTES
MONOCYTES
EOSINOPHILS
BASOPHILS
6000 /µL
60%
28%
8%
3%
1%
6000 /µL
3600 (2000-6900)
1680 (600-3400)
480 (0-900)
180 (0-700)
60 (0-100)
10
Neutrophilia
Neutropenia
• Causes
• Primary
– Myeloid leukemia
• Secondary
– Bacterial infections
• Associated bandemia
– Tissue necrosis
– Trauma
– Drugs – glucocorticosteroids, epinephrine
– Infection
• Viral including HIV
• Severe bacterial infections
– Drugs
– Autoimmune neutropenia
– Chronic idiopathic neutropenia
• Risk of Infection with Neutropenia (2000-6800/μL)
– Minimal risk with ANC < 1500
– Moderate risk with ANC <1000
– Severe risk with ANC <500
Eosinophilia
• Allergy
– Hayfever, asthma
– Drug hypersensitivity reactions
CASE STUDIES
• Parasitic infestation (non-protozoan)
• Sarcoidosis and collagen vascular diseases
• Malignancy (1%)
– Hodgkin’s disease
11
20 YEAR OLD with SORE THROAT
WBC
Patient 1 Patient 1 Normal Patient 2 Patient 2
Absolute absolute
20,000
14,000
PMNs
93%
LYMPHs
7%
MONOs
EOS
BASO
0
0
0
18000
1400
20006800
10004000
100-800
0-200
24%
3360
70%
9800
5%
1%
0
700
140
42 YEAR OLD WOMAN with
FEVER (103F) and LOW BACK PAIN
WBC
PMNs
BANDS
METAMYELOCYTES
LYMPHOCYTES
7,410/μL
95%
5%
7,410 / µL
72%
20%
7%
1%
APPENDICITIS – WBC COUNT
Patient
Ruptured
WBC Count
Neutrophilia
5 year old
18 year old
25 year old
27 year old
52 year old
30 year old
Yes
Yes
No
No
No
No
28,000
22,000
23,000
11,600
8,870
5,560
Yes
Yes
Yes
Yes
No
No
65 year old man with fatigue
and lymphadenopathy
WBC
PMNs
BANDS
LYMPHOCYTES
MONOCYTES
EOSINOPHILS
BASOPHILS
40,000 / µl
15%
0
83%
1%
1%
0
(4,500-11,000)
(45-70%)
(0-5%)
(25-44%)
(0-12%)
(1-8%)
(0-2%)
12
PLATELET INFORMATION
• Platelet count
– Thrombocytopenia < 150,000 mm3
– Thrombocytosis
> 600,000 mm3
• Mean platelet volume (MPV)
– Indicates size
(reference range 7.4-10.4 fl)
• Thrombocytopenia and:
– Large platelets → peripheral destruction
– Small platelets → production defect
SUMMARY - PEARLS
New Parameters on
Automated CBC Coming
• Available newer machines can measure
retiuclocytes and enumerate NRBCs
• In the near future:
– Extended differential count
• Bands and other immature granulocytes, inc blasts
• Atypical lymphocytes
• Erythroblasts
– Immature reticulocyte fraction
– Fragmented red blood cells
QUESTIONS ?
• The automated CBC provides accurate, useful
information re: rbc,wbc and platelets and newer
technology will yield even more parameters
• When anemia is present classify by MCV and
then order further studies
• WBC count and platelet count may direct you to
consider or dismiss conditions, but there is no
substitute for astute clinical judgment.
13