Automated CBC Parameters

and

Quality Control

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

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

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 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

CBCAdult Reference Ranges

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

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– Secondary=Manual

• When the Laboratory Information System (LIS) and the instrument are interfaced (connected) 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

Statistics involved

• Mean

• Standard Deviation• 1 S.D• 1 2 S.D• 1 3 S.D

• C.V

Levey – Jennings Chart

WestGard Interpretations

IQS in Hematology analyzer

• Commercial controls

• Retained Samples

Establishing Lab. Acceptable ranges for Controls

Establishing Lab control means• New lot of control should be analyzed in parallel

with current lot.• Run new control twice for five days• The mean of the 10 runs is then used.• A control file is set up for the new mean

Establishing Lab Acceptable range for controls ( S.D)

• Determined by evaluating 3- 6 months of data from the previous Q.C

• The individual S.D value is calculated

• The resultant S.D and Mean are used to monitor instrument performance

Retained sample testing

• A previous days ( retained) sample, stored at 2 – 8 C, with normal counts is run as 1st sample after the controls are analyzed. This is done on a daily basis.

• This sample is considered as the precision sample.

• This sample is then analyzed every one hour or / after 30 patient samples and also as the last sample before the analyzer is shutdown.

• The mean, S.D and C.V is calculated

Daily IQC of hematology analyzer

When a control point is outlier…

Other actions

Multi rule vs single rule QC in hematology analyzers

• A single rule QC procedure gives you all the error detection needed while at the same time maintaining low false rejections. This generally means eliminating the 12s rule because of its high false rejections and considering others such as 12.5s, 13s, and 13.5s

• Multi rule QC ( Westgard ) : Extra cost , more applicable in Chemistry lab.

• 13s refers to a control rule that is commonly used with a L-J chart when the control limits are set as the mean 3s .

• A run is rejected when a single control measurement exceeds the mean plus 3s or the mean minus 3s control limit

• 10x - reject when 10 consecutive control measurements fall on one side of the mean.

Systematic errors

Normal distribution curve