Automated CBC Parameters
and
Quality Control
Joanna Ellis, MLS(ASCP)
Revised Keri Brophy-Martinez
The Automated
Complete Blood Count
• Most common test in the Hematology lab.
• Main Components of the CBC:
–
–
–
–
Cell counts
Hgb
RBC indices
WBC differential absolute values and percent
• Indications for CBC:
–
–
–
–
–
–
Fatigue
Weakness
Infection
Inflammation
Bruising
Bleeding
CBC Parameters
PARAMETER
UNIT OF REPORTING
COMMON METHOD OF DETERMINATION
WBC
X 103 /µL
Impedance count X calibration (cal) factor
RBC
X 106 /µL
Impedance count X calibration factor
HGB
g/dL
Colorimetric absorbance in proportion to hemoglobin
MCV
fL
From RBC histogram,
#of RBCs X size of RBCs X cal constant OR Calculated: HCT X 10
RBC
HCT
%
Calculated: RBC X MCV
10
MCH
Pg
MCHC
g/dL or %
Calculated: HGB X 100
HCT
RDW
%
Impedance (from histogram)
Platelet
X 103 /µL
Impedance count X cal factor
WBC Diff
Absolute: X103 /µL
Percent of WBC : %
Light Scatter , flow cytometry
Calculated:
HGB X 10
RBC
M77221
CBC
Adult Reference Ranges
Parameter
Adult Reference Range
WBC
4.5-11.0 X 103/µL
RBC
Male: 4.5-5.5 X 106 /µL
Female: 4.0-5.0 X 106 /µL
HGB
Male: 14-17.4 g/dL
Female: 12.0-16.0 g/dL
HCT
Male: 42-52%
Female: 36-46%
MCV
80-100 fl
MCH
28-34 pg
MCHC
32-36 g/dL or %
RDW
12.0-14.6%
PLT
150-450 X 103 /µL
MPV
6.8-10.2 fl
Linearity
(Reportable Range)
• Instruments are calibrated for each analyte with a
range that is clinically relevant.
• With concentrations above or below the
reportable range or Linearity range, the result
does not correspond with the calibration curve in
linear fashion.
• Results outside of linearity are NOT acceptable.
• Linearity ranges vary by instrument.
– Example:
Parameter
Coulter STKS
Advia
WBC
0.0 -99.9 X 103 /µL
0.02-400 X 103 /µL
Advia
Linearity Instrument Codes
Code
Cause
Action Indicated
+++++
Result exceeds reportable
range
Dilute 1:2 and rerun.
Continue further dilutions
until result is within linearity
H
Result higher than the
laboratory set patient high
action limit
Review Result
L
Result is lower than the
laboratory set patient low
action limit
Review Result
CBC Quality Control
• Commercial Controls:
• 3 levels (low, normal, high)
• Values stored in instrument computer
• Levey-Jennings graph generated and stored for each parameter
• Mode to Mode QC:
• Most automated hematology instruments have a primary and
secondary mode of sample aspiration. Controls must be run on
BOTH and correlate.
– Primary=Automated or Closed
– Secondary=Manual or Open
• Delta Checks
• When the Laboratory Information System (LIS) and the instrument
are interfaced (connected) delta checks are conducted by the LIS
on select parameters.
– Current values compared to most previous result
– Differences greater than the limits set within the LIS are
flagged
WBC Parameter
Interfering substances and Implications
Test
Name
Interfering Agent
Clinical Implications
LOW <4.5 X103 /µL
•some medications (such as
methotrexate),
•some autoimmune conditions
•some severe infections
•bone marrow failure
•Unusual RBC abnormalities that
resist lysis
•Nucleated RBCs
White
•Fragmented WBCs
Blood
WBC
•Unlysed particles greater than 35 fL
Cell
•Very large or aggregated plts
Count
HIGH: >11.0 X103 /µL
•Specimens containing fibrin, cell
•Infections
fragments or other debris (esp
•Inflammation
pediatric/oncology specimens
•cancer, leukemia
RBC Parameter
Interfering substances and Implications
Test
RBC
Name
Red
Blood
Cell
Count
Interfering Agent
•Very high WBC count (greater than 99.9)
•High concentration of very large platelets
•Agglutinated RBCs, rouleaux will break up
when Istoton is added
•RBCs smaller than 36 fL
•Specimens containing fibrin, cell fragments or
other debris (esp pediatric/oncology specimens
Clinical Implications
LOW:
Male: < 4.5 X 106 /µL
Female: < 4.0 X 106 /µL
•Anemia
HIGH:
Male: > 5.5 X 106 /µL
Female: > 5.0 X 106 /µL
•Polycythemia vera,
•fluid loss due to
diarrhea, dehydration,
buns
HGB Parameter
Interfering substances and Implications
Test
HGB
Or
Hb
Name
Interfering Agent
•Very high WBC count
•Severe lipemia
•Heparin
•Certain unusual RBC abnormalities
Hemoglobin that resist lysing
•Anything that increases the turbidity
of the sample such as elevated levels
of triglycerides
•High bilirubin
Clinical Implications
LOW:
Male: <14 g/dL
Female: <12.0 g/dL
•Anemia
HIGH:
Male: > 17.4 g/dL
Female: >16.0 g/dL
•Polycythemia vera
•fluid loss due to diarrhea,
dehydration, burns
HCT Parameter
Interfering substances and Implications
Test
Name
Interfering Agent
Clinical Implications
LOW:
Male: <42%
Female: <36%
•Anemia
HCT
Hematocrit
•Known factors that interfere with the
parameters used for computation, RBC HIGH:
and MCV
Male: >52%
Female: <46%
•Polycythemia vera
•fluid loss due to diarrhea,
dehydration, burns
MCV Parameter
Interfering substances and Implications
Test
Name
Interfering Agent
•Very high WBC count
•High concentration of very large
Mean
platelets
Corpuscular
MCV
•Agglutinated RBCs
(Cell)
•RBC fragments that fall below the 36 fL
Volume
threshold
•Rigid RBCs
Clinical Implications
LOW: <80 fL
•Iron deficiency anemia
•Thalassemia
HIGH: >100 fL
•B12
•Folate Deficiency
RDW Parameter
Interfering substances and Implications
Test
Name
Interfering Agent
•Very high WBC
•High concentration of very large or
Red Cell
clumped platelets
RDW Distribution •RBCs below the 36 fL threshold
Width
•Two distinct populations of RBCs
•RBC agglutinates
•Rigid RBCs
Clinical Implications
HIGH: >14.6%
•Mixed population of RBCs
•Immature RBCs tend to
be larger
Plt Parameter
Interfering substances and Implications
Test
Plt
Name
Platelet
Count
Interfering Agent
•Very small red cells near
the upper threshold
•Cell fragments
•Clumped platelets
•Cellular debris near the
lower platelet threshold
Clinical Implications
LOW: < 150 X 103 /µL
•Bleeding
•Wiskott-Aldrich,
•Bernard-Soulier
•Systemic lupus erythematosus
•Pernicious anemia
•Hypersplenism (spleen takes too many out
of circulation)
•Leukemia
•Chemotherapy
HIGH: >450 X 103 /µL
•Benign idiopathic thrombocytosis
•Myeloproliferative disorders
•Polycythemia vera
WBC Differential Parameters
Clinical Implications in Adults
Test
Name
Clinical Implications of
LOW %
Clinical Implications of HIGH %
Neut %
Neutrophil %
In 100 WBC
differential
LOW: <40%
•Chemotherapy
•Severe infection
HIGH: >80%
•Bacterial infection
•Inflammatory disease
•Chronic myelogenous leukemia
Lymph %
Lymphocyte %
•LOW: <25%
•Lupus
•Later stages of HIV infection.
•HIGH: >35%
•Viral infection
•Chronic or Acute Lymphocytic Leukemia
Mono %
Monocyte %
LOW: <2%
•Bone Marrow Insufficiency
HIGH: >10%
•Inflammatory disorders
•Myelomonocytic leukemia
Eos %
Eosinophil %
HIGH: >5%
•Parasitic infection
•Allergic reaction
Baso %
Basophil %
HIGH: >1%
•Allergic reaction to food
•Chronic inflammation
Affect of Hemolysis on CBC Parameters
PARAMETER
AFFECT
WBC
Probably unaffected
RBC
Falsely low due to RBC lysis and/or RBC fragments not be counted as
RBCs
HGB
Reportable- accurate measurement relies on RBCs being completely
lysed
HCT
Falsely low- calculated with an invalid MCV and falsely low RBC
MCV
Invalid falsely low or high depending on the degree of hemolysis. May be
falsely low if RBC fragments cause smaller pulses to be produced in the
RBC aperature or falsely high if fragmented RBCs fall below the RBC
threshold and are not counted.
MCH
Invalid- calculated with a falsely low RBC
MCHC
Invalid- calculated with a falsely low HCT
RDW
Falsely high due to RBC fragments increasing the CV of the RBC
histogram
PLT
Falsely high due to RBC fragments being incorrectly counted as platelets
References
•Harmening., Denise, Clinical Hematology and Fundamentals of
Hemostasis,
3rd edition, pp. 593-599.
•Turgeon, Mary Louise, Clinical Hematology - Theories and Procedures,
3rd edition, pp373, 376-382.
•Rodak, Bernadette, Diagnostic Hematology, 1st edition, p.605-606.
Coulter STKS Operating Manual
•McKenzie, Shirlyn, Clinical Laboratory Hematology, 2nd edition,pp
813-829.
•"Complete Blood Count: The Test." Lab Tests Online: Welcome!
American Association for Clinical Chemistry, 18 June 2010.
Web. 13 Sept. 2010.
<http://www.labtestsonline.org/understanding/analytes/cbc
/test.html#how>.
•"WBC Differential Count: The Test." Lab Tests Online: Welcome! American
Association for Clinical Chemistry, 18 June 2010. Web. 13 Sept.
2010.http://www.labtestsonline.org/understanding/analytes/dif
ferential/test.html#what>.