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“Quality Control” in Hematology. June 14, 2013. M R Tiwari M.Sc -TQM. Laboratory test results (Good laboratory practice, GLP) Clinical diagnosis Patient management. Good Laboratory Practice. Quality can be assured at Pre-analytical stage Analytical stage Post-analytical stage.

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Quality control in hematology

“Quality Control” in Hematology

June 14, 2013

M R Tiwari

M.Sc-TQM


Laboratory test results

(Good laboratory practice, GLP)

Clinical diagnosis

Patient management


Good laboratory practice
Good Laboratory Practice

Quality can be assured at

  • Pre-analytical stage

  • Analytical stage

  • Post-analytical stage



Terminologies
Terminologies

=

QC at Analytical stage


Precision reproducibility
PRECISION (REPRODUCIBILITY)

  • Definition

    Precision refers to the reproducibility of a result.

  • Comparing QC terms to a targetFigure illustrates that the results are precise (close together) but not accurate (they are not in the bull’s-eye).

  • Checking precision is required while

    -calibration

    -troubleshooting

QC at Analytical stage


Accuracy
ACCURACY

  • Definition

    Closeness of a result to the true (accepted) value.

    NOTE: Before determining accuracy, first determine precision.

  • Comparing QC terms to a targetFigure illustrates that the results are accurate (in the bull’s-eye) and precise (close together).

    NOTE

  • You cannot have accuracy without precision.

  • However, you can have precision without accuracy.

QC at Analytical stage


Neither accuracy not precision
NEITHER ACCURACY NOT PRECISION

  • This figure illustrates that the results are neither accurate nor precise.

  • None of the results are close together, and none of them are in the bull’s-eye.

QC at Analytical stage


Statistics involved
Statistics involved…

  • Mean

  • Standard deviation (SD)

    • ± 1SD

    • ± 2SD

    • ± 3SD

  • Coefficient of variation (%CV)

QC at Analytical stage


Hematology analyzers

QC at Analytical stage


Technical specifications
Technical Specifications

QC at Analytical stage



Precision

QC at Analytical stage


Test selectivity / Throughputs

QC at Analytical stage


Sample Modes / Volumes

QC at Analytical stage


Calibration setting accuracy

Calibration (setting accuracy)

Hematology analyzer


Setting accuracy
Setting accuracy

Calibration

Is done to standardize the instrument for accuracy.

Calibrator

Certified Reference Material (CRM) used to calibrate a measurement on an analyzer.

Cal-Factors

If any deviation from calibration references is observed necessary calibration correction factors are applied to set the accuracy of the instrument.

QC at Analytical stage


Calibration
Calibration

  • Pre-calibration check

    • Total maintenance of the instrument

    • Reagents (replenish or replace)

    • Calibrator (Check for expiry)

  • Calibration procedure

    • Precision check

    • Carryover check

    • Calibration in both (open and closed modes)

  • Post-calibration validation

    • Run calibrator as samples

    • Run 3 level controls

QC at Analytical stage


Carryover
CARRYOVER

  • Carryover is defined as a number of cells

    remaining behind following the cycling of a blood sample.

  • This test is performed to determine if one sample interferes with the accurate analysis of the next sample.

  • Ideally, carryover shall be very low.

  • Measure a specimen with a high concentration in triplicate, immediately followed by a specimen with a low concentration in triplicate.

  • Where l1 and l3 are the results of the first and third measurements of the samples with a low concentration and h3 is the third measurement of the sample with a high concentration.

QC at Analytical stage



Daily iqc in hematology analyzers
Daily IQC in hematology analyzers

  • Commercial controls

  • Retained sample

  • Moving averages (Bull’s algorithm)

QC at Analytical stage


Daily iqc of hematology analyzer
DAILY IQC of Hematology analyzer

QC at Analytical stage


Control chart s inventor

In 1931,

Dr. Walter Shewhart, a scientist at the Bell Telephone Laboratories, proposed applying statistical based control charts to interpret industrial manufacturing processes.

In 1950,

S. Levey&

E.R. Jennings

suggested the use in the clinical laboratory.

Control Chart's Inventor

QC at Analytical stage


Establishing Laboratory’s acceptable ranges for controls Reference : CELL-DYN Sapphire Operator’s Manual, 11-16

Establishing laboratory control mean

Commercial controls

  • New lot of control material should be analyzed in parallel with current lot.

  • This may be accomplished by running the new controls twice a day for five days (we run three times for three days and one time on fourth day).

  • The mean of the ten runs is then used.

  • A control file is set up for the new mean.

  • The same file is used to run control for the reminder dating of period.

QC at Analytical stage


Establishing Laboratory’s acceptable ranges for controls Reference : CELL-DYN Sapphire Operator’s Manual, 11-16

Establishing laboratory acceptable ranges (SD)

Commercial controls

  • The expected ranges published by the manufacturers do not represent standard deviations and are generally too broad for effective quality control.

  • These ranges are determined by evaluating three to six months of data (data from the previous IQC) for a particular level of control.

  • The individual SD values may be averaged as follows:

N = number of values in a group

SD = Standard Deviation of the values in that group

i = the last group of values

The resultant long-term instrument SD and the laboratory established mean

is used to monitor instrument performance

QC at Analytical stage


L-J chart Interpretation

Dr. James O Westgard

QC at Analytical stage


Modification

of 10x

Dr. James O Westgard

QC at Analytical stage


×

I prefer the ‘xyz’ analyzer because

its 2SD QC charts are amazingly flat

2SD

QC at Analytical stage


Retained sample testing
Retained sample testing

  • A previous days (retained) sample, stored at 2-80C, 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 shut down.

  • The mean, SD and CV is monitored.

QC at Analytical stage


When a control point is outlier
When a control point is outlier…

Warning rule = use other rules to inspect the control points

Rejection rule = “out of control”

  • Stop testing

  • Identify and correct problem

  • Repeat testing on patient samples and controls

  • Do not report patient results until problem is solved and controls indicate proper performance

QC at Analytical stage


Other additive iqcs
Other additive IQCs

QC at Analytical stage


Flags correlation with pbs
Flags & correlation with PBS

QC at Analytical stage


Pbs examination
PBS examination

  • Ensure good drying of the smear

  • Do not use overused stains

  • Maintain required pH of the buffer

  • Maintain the staining time

A good smear

Quality tips

QC at Analytical stage


Flag 1
Flag 1

  • ? Suspect BLASTS

  • ? Monocytosis

PBS correlation

Analyzer

PBS : Monocytes / Blasts

QC at Analytical stage


Flag 2
Flag 2

  • ? Suspect BLASTS

  • ? Lymphocytosis

  • ? Variant lymphocytes

PBS correlation

Analyzer

PBS : Lymphocytes / Blasts

QC at Analytical stage


Flag 3
Flag 3

  • ? Platelet clumps

  • Thrombocytopenia

PBS correlation

Analyzer

PBS : Platelet clumps /

QC at Analytical stage


Flag 5
Flag 5

  • ? Giant Platelets

  • Thrombocytopenia

PBS correlation

Analyzer

PBS : Giant platelets

QC at Analytical stage


External quality assessment proficiency testing
External Quality Assessment(Proficiency testing)

QC at Analytical stage


Normal Distribution Curve

or

Gaussian curve

Describes events or data that occur symmetrically about the mean.

Out of 100 events

68.7 will fall within ±1 SD

95.4 will fall within ± 2 SD

99.7 will fall within ±3 SD

QC at Analytical stage


Comparative performance evaluation
Comparative performance evaluation

Z-Score

QC at Analytical stage


If eqas pt is not available
If EQAS/PT is not available

QC at Analytical stage


If eqas results are out
If EQAS results are out

QC at Analytical stage


Summary
Summary…

Laboratory test results

  • Pre-analytical stage

  • Analytical stage

  • Post-analytical stage

Clinical diagnosis

Patient management

Quality

Good Laboratory Practice

Thank you…


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