Download - CBC Parameters and QC.ppt
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Automated CBC Parameters
and
Quality Control
Joanna Ellis, MLS(ASCP)
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The Automated
Most common test in the Hematology lab.Main Components of the CBC:Cell countsHgbRBC indicesWBC differential absolute values and percentIndications for CBC:FatigueWeaknessInfectionInflammationBruisingBleeding
Complete Blood CountThe 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.
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CBC Parameters
PARAMETERUNIT OF REPORTINGCOMMON METHOD OF DETERMINATIONWBCX 103 /LImpedance count X calibration (cal) factorRBCX 106 /LImpedance count X calibration factorHGBg/dLColorimetric absorbance in proportion to hemoglobinMCVfLFrom RBC histogram, #of RBCs X size of RBCs X cal constant OR Calculated: HCT X 10 RBCHCT%Calculated: RBC X MCV 10MCHPgCalculated: HGB X 10 RBCMCHCg/dL or %Calculated: HGB X 100 HCTRDW%Impedance (from histogram)PlateletX 103 /LImpedance count X cal factorWBC DiffAbsolute: X103 /LPercent of WBC : %Light Scatter , flow cytometryWe 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.
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M77221
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CBC
ParameterAdult Reference RangeWBC4.5-11.0 X 103/LRBCMale: 4.5-5.5 X 106 /LFemale: 4.0-5.0 X 106 /LHGBMale: 14-17.4 g/dLFemale: 12.0-16.0 g/dLHCTMale: 42-52%Female: 36-46%MCV80-100 flMCH28-34 pgMCHC32-36 g/dL or %RDW12.0-14.6%PLT150-450 X 103 /LMPV6.8-10.2 fl
Adult Reference RangesThis chart can also be found in on the first page of the textbook.
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Linearity
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: ParameterCoulter STKSAdviaWBC0.0 -99.9 X 103 /L0.02-400 X 103 /L
(Reportable Range)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.
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Advia
CodeCauseAction Indicated+++++Result exceeds reportable rangeDilute 1:2 and rerun.Continue further dilutions until result is within linearityHResult higher than the laboratory set patient high action limitReview ResultLResult is lower than the laboratory set patient low action limitReview Result
Linearity Instrument CodesThese 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.
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CBC Quality Control
Commercial Controls:
3 levels (low, normal, high)Values stored in instrument computerLevey-Jennings graph generated and stored for each parameterMode 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 ClosedSecondary=Manual or OpenDelta 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 resultDifferences greater than the limits set within the LIS are flagged*
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WBC Parameter
TestNameInterfering AgentClinical ImplicationsWBCWhite Blood Cell CountUnusual RBC abnormalities that resist lysisNucleated RBCsFragmented WBCsUnlysed particles greater than 35 fLVery large or aggregated pltsSpecimens containing fibrin, cell fragments or other debris (esp pediatric/oncology specimensLOW 11.0 X103 /LInfectionsInflammationcancer, leukemia
Interfering substances and Implications*
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RBC Parameter
TestNameInterfering AgentClinical ImplicationsRBCRedBlood Cell CountVery high WBC count (greater than 99.9)High concentration of very large plateletsAgglutinated RBCs, rouleaux will break up when Istoton is addedRBCs smaller than 36 fLSpecimens containing fibrin, cell fragments or other debris (esp pediatric/oncology specimensLOW:Male: < 4.5 X 106 /LFemale: < 4.0 X 106 /LAnemiaHIGH:Male: > 5.5 X 106 /LFemale: > 5.0 X 106 /LPolycythemia vera,fluid loss due to diarrhea, dehydration, buns
Interfering substances and Implications*
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HGB Parameter
TestNameInterfering AgentClinical ImplicationsHGBOr HbHemoglobinVery high WBC countSevere lipemiaHeparinCertain unusual RBC abnormalities that resist lysingAnything that increases the turbidity of the sample such as elevated levels of triglyceridesHigh bilirubinLOW:Male: 16.0 g/dLPolycythemia verafluid loss due to diarrhea, dehydration, burns
Interfering substances and Implications*
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HCT Parameter
TestNameInterfering AgentClinical ImplicationsHCTHematocritKnown factors that interfere with the parameters used for computation, RBC and MCVLOW: Male:
Interfering substances and Implications -
MCV Parameter
TestNameInterfering AgentClinical ImplicationsMCVMean Corpuscular (Cell) VolumeVery high WBC countHigh concentration of very large plateletsAgglutinated RBCsRBC fragments that fall below the 36 fL thresholdRigid RBCsLOW: 100 fLB12 Folate Deficiency
Interfering substances and Implications*
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RDW Parameter
TestNameInterfering AgentClinical ImplicationsRDWRed Cell Distribution WidthVery high WBCHigh concentration of very large or clumped plateletsRBCs below the 36 fL thresholdTwo distinct populations of RBCsRBC agglutinatesRigid RBCsHIGH: >14.6%Mixed population of RBCsImmature RBCs tend to be larger
Interfering substances and Implications*
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Plt Parameter
TestNameInterfering AgentClinical ImplicationsPltPlatelet CountVery small red cells near the upper thresholdCell fragmentsClumped plateletsCellular debris near the lower platelet thresholdLOW: < 150 X 103 /LBleedingWiskott-Aldrich,Bernard-SoulierSystemic lupus erythematosusPernicious anemiaHypersplenism (spleen takes too many out of circulation)LeukemiaChemotherapyHIGH: >450 X 103 /LBenign idiopathic thrombocytosisMyeloproliferative disordersPolycythemia vera
Interfering substances and Implications*
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WBC Differential Parameters
TestNameClinical Implications of LOW %Clinical Implications of HIGH %Neut %Neutrophil %In 100 WBC differentialLOW: 80%Bacterial infectionInflammatory diseaseChronic myelogenous leukemiaLymph %Lymphocyte %LOW: 35%Viral infectionChronic or Acute Lymphocytic LeukemiaMono %Monocyte %LOW: 10%Inflammatory disordersMyelomonocytic leukemiaEos %Eosinophil %HIGH: >5%Parasitic infection Allergic reactionBaso %Basophil %HIGH: >1%Allergic reaction to foodChronic inflammation
Clinical Implications in Adults*
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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. ."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/differential/test.html#what>.*