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Automated CBC Parameters Quality Control

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1 Automated CBC Parameters Quality Control
and Quality Control Joanna Ellis, MLS(ASCP)

2 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 The CBC is a very common test. Many patients will have baseline CBC tests to help determine their general health status. If they are healthy and they have cell populations that are within normal limits, then they may not require another CBC until their health status changes or until their doctor feels that it is necessary. If a patient is having symptoms such as fatigue or weakness or has an infection, inflammation, bruising, or bleeding, then the doctor may order a CBC to help diagnose the cause.

3 COMMON METHOD OF DETERMINATION
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 HCT % Calculated: RBC X MCV 10 MCH Pg Calculated: HGB X 10 MCHC g/dL or % Calculated: HGB X 100 RDW Impedance (from histogram) Platelet Impedance count X cal factor WBC Diff Absolute: X103 /µL Percent of WBC : % Light Scatter , flow cytometry We have discussed the principles of impedance, colorimetric determinations, light scatter, and flow cytometry in the previous powerpoints. This chart simplifies the parameter, the units of reporting, and the most commonly used method of determination.

4 M77221

5 CBC Adult Reference Ranges
Parameter Adult Reference Range WBC X 103/µL RBC Male: X 106 /µL Female: X 106 /µL HGB Male: g/dL Female: g/dL HCT Male: % Female: % MCV fl MCH 28-34 pg MCHC 32-36 g/dL or % RDW % PLT X 103 /µL MPV fl This chart can also be found in on the first page of the textbook.

6 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: The instrument will be accurate as long as the results fall within a certain range known as the linearity range also known as the reportable range. When patient results are higher or lower than the reportable range, the results do not match up the standard curve or calibration curve in a straight line; therefore, they cannot be standardized. The results cannot be reported. Some instruments FLAG these results, others give values of greater than the highest reportable value. Many times the specimen will need to be diluted, rerun and the result multiplied by the dilution factor to get a result within linearity. Parameter Coulter STKS Advia WBC X 103 /µL X 103 /µL

7 Advia Linearity Instrument Codes
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 These codes are on the CBC results sheet when a certain parameter is beyond set limits. There are abnormal results that generate flags or abnormal codes. We will be discuss the document “Handling Abnormal Results” next.

8 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

9 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

10 RBC Parameter Interfering substances and Implications
Test Name Interfering Agent Clinical Implications RBC Red Blood 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 /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

11 HGB Parameter Interfering substances and Implications
Test Name Interfering Agent Clinical Implications HGB Or 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/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

12 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

13 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

14 RDW Parameter Interfering substances and Implications
Test Name Interfering Agent Clinical Implications RDW Red 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

15 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

16 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

17 References Harmening., Denise, Clinical Hematology and Fundamentals of Hemostasis, 3rd edition, pp Turgeon, Mary Louise, Clinical Hematology - Theories and Procedures, 3rd edition, pp373, Rodak, Bernadette, Diagnostic Hematology, 1st edition, p Coulter STKS Operating Manual McKenzie, Shirlyn, Clinical Laboratory Hematology, 2nd edition,pp "Complete Blood Count: The Test." Lab Tests Online: Welcome! American Association for Clinical Chemistry, 18 June Web. 13 Sept <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 Web. 13 Sept http://www.labtestsonline.org/understanding/analytes/dif ferential/test.html#what>.


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