Automated CBC Parameters

and

Quality ControlJoanna 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 ParametersPARAMETER 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 fLFrom 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 Calculated: HGB X 10 RBC

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 /µLPercent of WBC : % Light Scatter , flow cytometry

M77221

CBCAdult Reference RangesParameter Adult Reference Range

WBC 4.5-11.0 X 103/µL

RBC Male: 4.5-5.5 X 106 /µLFemale: 4.0-5.0 X 106 /µL

HGB Male: 14-17.4 g/dLFemale: 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

HResult higher than the

laboratory set patient high action limit

Review Result

LResult 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

WBC

White Blood Cell

Count

•Unusual RBC abnormalities that resist lysis•Nucleated RBCs•Fragmented WBCs•Unlysed particles greater than 35 fL•Very large or aggregated plts•Specimens containing fibrin, cell fragments or other debris (esp pediatric/oncology specimens

LOW <4.5 X103 /µL•some medications (such as methotrexate), •some autoimmune conditions•some severe infections•bone marrow failure

HIGH: >11.0 X103 /µL•Infections•Inflammation•cancer, leukemia

RBC Parameter Interfering substances and Implications

Test Name Interfering Agent Clinical Implications

RBC

RedBlood Cell

Count

•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

LOW:Male: < 4.5 X 106 /µLFemale: < 4.0 X 106 /µL•Anemia

HIGH:Male: > 5.5 X 106 /µLFemale: > 5.0 X 106 /µL•Polycythemia vera,•fluid loss due to diarrhea, dehydration, buns

HGB Parameter Interfering substances and Implications

Test Name Interfering Agent Clinical Implications

HGBOr Hb

Hemoglobin

•Very high WBC count•Severe lipemia•Heparin•Certain unusual RBC abnormalities that resist lysing•Anything that increases the turbidity of the sample such as elevated levels of triglycerides•High bilirubin

LOW:Male: <14 g/dLFemale: <12.0 g/dL•Anemia

HIGH:Male: > 17.4 g/dLFemale: >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

HCT Hematocrit•Known factors that interfere with the parameters used for computation, RBC and MCV

LOW: Male: <42%Female: <36%•Anemia

HIGH:Male: >52%Female: <46%•Polycythemia vera•fluid loss due to diarrhea, dehydration, burns

MCV Parameter Interfering substances and Implications

Test Name Interfering Agent Clinical Implications

MCV

Mean Corpuscular

(Cell) Volume

•Very high WBC count•High concentration of very large platelets•Agglutinated RBCs•RBC fragments that fall below the 36 fL threshold•Rigid RBCs

LOW: <80 fL•Iron deficiency anemia•Thalassemia

HIGH: >100 fL•B12 •Folate Deficiency

RDW Parameter Interfering substances and Implications

Test Name Interfering Agent Clinical Implications

RDWRed Cell

Distribution Width

•Very high WBC•High concentration of very large or clumped platelets•RBCs below the 36 fL threshold•Two distinct populations of RBCs•RBC agglutinates•Rigid RBCs

HIGH: >14.6%•Mixed population of RBCs•Immature RBCs tend to be larger

Plt Parameter Interfering substances and Implications

Test Name Interfering Agent Clinical Implications

Plt Platelet Count

•Very small red cells near the upper threshold•Cell fragments•Clumped platelets•Cellular debris near the lower platelet threshold

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 ParametersClinical 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

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

Affect of Hemolysis on CBC Parameters

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>.