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 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.

COMMON METHOD OF DETERMINATION 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 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.

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 This chart can also be found in on the first page of the textbook.

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 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 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