Quality control.pptx

QUALITY CONTROL IN HEMATOLOGY
N. Madhumidha
I yr PG
Department of Pathology

• What is quality ?
– Means that a product should meet its specification.
• Quality Control
– Refers to the measure that must be included during each assay run to verify
that the test is working properly, according to pre established
specifications.

• Quality Assurance
– Defined as the overall program that ensures that the final results
reported by the laboratory are correct.
– Concerned with that the “ right test is carried out on the right
specimen and the right result and right interpretation is delivered
to the right person at the right time.”

Quality Assurance Quality Control
An overall management plan
to guarantee the integrity of
data
( the “system” )
A series of analytical
measurements used to assess
the quality of the analytical
data
( the “tool” )

Quality control
+
Quality assessment
=
Quality assurance

• 3 major activities of quality assurance
– Preventive – activities that are done prior to the examination of the
specimen eg. Preventive maintainance and calibration of instruments,
orientation and training of personnel.
– Assessment – those activities that are done during testing to determine
whether the test system are performing correctly eg. The use of standard
and controls, maintainance of control charts.
– Corrective – those activities that are done, when error is detected to correct
the system. Eg. Equipment troubleshooting, recalibration of instruments.

• Objective
• Accuracy
– It is the closeness of the estimated value to the true mean.
– It can be checked by the use of reference materials which have been
assayed by independent methods of known precicion.
• Precision
– It is the closeness of repeated measures to each other.

Precision = Repeatability or reproducibility
Accuracy = Trueness + Precision.

• Before the analysis
Pre analytical
• During the analysis
Analytical
• After the analysis
Post analytical

Prescription
Patient
Preparation
Registration Collection Transport Receiving

Sample
Preparation
Equipment
Manangement
Reagent
Manangement
Quality
Assurance
Analysis

Report
validation
Report
Preparation
Report
Despatch
Data
Archival
Sample
storage
Sample
Discarding

 Pre-examination components
 Patient test requisitions
 Patient preparation
 Sample collection
 Sample transport
 Sample processing
 Sample storage
 Phlebotomy training

Order of draw
1. Blood culture tubes ( yellow )
2. Coagulation sodium citrate tube ( blue stopper )
3. Serum tubes
4. Heparin tubes ( green stopper )
5. ETDA tbes ( lavender stopper )
6. Glycolytic inhibitor tubes ( gray stopper )

 Examination components
 Test method/procedure
 Reagents
 Internal quality control
 External quality control (proficiency testing)
 Instrument maintenance

 Internal quality control is a set of procedures for continuously assessing laboratory
work and emergent results .
 It is primarily a check of precision.
 It includes
 Control charts with tests on control materials
 Duplicate tests on all specimens or on a proportion of the specimens
 Delta check, comparing current test results with previous results
 Consistency of mean values of patient data;
Correlation check (e.g., blood film features or sensibility of interrelated
parameters)
INTERNAL QUALITY CONTROL

 Control charts with tests on control materials
 Samples of the control specimen are included in every batch of the
patient’s specimens and the results are checked on a control chart.
 To check precision, it is not necessary to know the exact value of
the control specimen.

 Control material
 A control is a “ patient like ” sample composed of one or many
constituents whose concentration are known.
 Controls are device or material for checking that the performance of a
test is constant.
 Preferably one should have controls of high, normal and low values.
 Two different concentrations are necessary for adequate statistical QC.
 The same material can be used for external QC or also a calibrator.
 Control specimen may be three types
Pure solutions
 Liquid serum preparation
 Lyophilized control specimen

Minimum of one level QC atleast once a day
Patient samples >25 per day – Employ 2 levels of QC atleast
once a day
Patient samples >75 per day – Employ 2 levels of QC atleast
twice a day
Control must be treated exactly like the patient’s
specimens

 Calibrators
 Solutions with specified defined concentration that are used to
set or calibrate an instrument.
 Cannot be used as a control.
When used control to check the precision of a test, it is not
necessary to know the true concentration of the substance to be
measured.
 But when the material is intended for use as a calibrator, it must
have an assigned value

Controls Calibrators
• Used to check calibration of a test
system
• Controls are pools of serum or
plasma
• Less expensive
• Add analytes to get normal and
abnormal controls
• Used to calibrate a test system
• Calibrators are extremely accurate
• Expensive

 Duplicate test on patient’s specimen
 It provide another way of checking the precision of routine
work.
Ten consecutive specimens are tested in duplicate under careful
condition.
Difference between the pairs of results are calculated and
standard deviation is derived.
Subsequent duplicate tests should not differ from each other by
more than 2SD
This method will detect random errors but it is not sensitive
It is impractical for routine blood counts in busy lab.

 Delta Check
 It rely on consecutive testing of a particular patient.
 Comparison of current hematology results to the most recently
reported previous result for a given patient

 Correlation Check
 It implies that any unexpected result of a test must be checked to see whether
it can be explained on clinical ground or whether it correlates with other tests.
 Eg. 1. Low MCHC confirmed by hypochromic red cells on peripheral smear.
 2. High MCV must correlate with macrocytosis.
 3. Marked leukocytosis, thrombocytopenia and thrombocytosis needs
peripheral smear examinations.

 Bull’s Algorithm
 Brain Bull ( an American hematologist) establish a new quality
control method to detect systematic error in erythrocyte indexes.
A Moving average is calculated instead of mean value
 Its main idea is to estimate the mean value of the last twenty
patient’s value, including in them the mean of the batch of the
previous twenty value.

 Since 1960s, many laboratories have participated in proficiency testing surveys
such as CAP survey program.
 CLIA’88 mandated that all clinical laboratories should participate in a proficiency
testing survey atleast three times a year.
 It consists of unknown samples of whole blood or lypholized serum/plasma
representing the values that would be expected in patients sample.
 Samples sent to the laboratory and test with the normal sample batch with no
special treatment.
 Result are sent to the sample provider for statistical analysis.
 The survey provider determine the target value for each test result through
comparison studies with peer laboratories and establish the acceptable performance
ranges.
EXTERNAL QUALITY CONTROL

Analysis of EQA data
Deviation index for CBC
Mean, SD are calculated by EQA lab comparing the
participating lab’s performance with peer laboratories and
with true value.
Performance is measured by DI
DI = ( actual result – mean) / SD

DI score
<0.5% - excellent
0.5-1% - satisfactory
1-2% - acceptable
2-3% - calibration to be checked
>3% - serious defect

 Random error
An error which varies in an unpredictable manner, in magnitude
and sign, when a large number of measurements of the same
quality are made under identical condition.
 Systematic error
 An error which, in the course of a number of measurements of
the same value of a given quantity, remains constant when
measurements are made under the same condition
ERRORS IN MEASUREMENTS

Systematic error Random error
Errors within the test
system/method
Caused by incorrect calibration,
malfunction of components,
failure of some path of testing
process, change in reagents,
expired, improper storage
It affects accuracy
Errors occuring without
prediction/regularity
Caused by poor calibration,
instrument instability, operator
and temperature variabilty
It affects accuracy and precision

 Mean – is the total score of all measurements divided by the number of
measurements.
STATISTICS OF QC - Mean

 Standard deviation – is a measure of how much the data varies around the mean
 Used to measure dispersion / scattering of a group of values around a mean
 Primary indicator of precision
 Measure of random error.
Standard deviation

 Coefficient of variation – is SD expressed as a proportion of mean
 It gives the relation of SD to the actual measurement
 Comparison of overall precison, since the standard deviation typically
increases as the concentration of the analyte increases.
Coefficient of variation

 Ranges of Control Charts
 Once the mean and the SD derived, the range of acceptability can be assigned.
Using the SD, a chart can be developed to monitor the daily control values.
Usually the range of acceptability is + 3SD.

 How to calculate control limits?
 20-30 successive measurements from any control levels
 SD and mean calculated
The range mean + 3SD is considered as trial limit
If the measurments exceeds the range mean + 3SD then the
outliner is rejected.

• A graphical method for displaying control results and evaluating whether a
procedure is in - control or out - of – control.
• The first step is to calculate the control limits. Standard deviation is commonly
used to set the limits.
• The chart is created for each test and level of control.
• Daily control values should be plotted against time.
• Lines are drawn from point to point.
Levey – Jennings ( L J ) chart

• Rules of how to use LJ chart correctly described by Dr. JAMES WESTGARD.
• Westgard has formulated rules to decide whether an analytical run is in – control or
out – of – control.
•These rules can be applied as single rules and as a group of rules ( multi rules )
•These rules can be applied only if your QCs are plotted with the range of 3SD.
WESTGARD RULES

•Have to understand 2 sets of nomenclatures
1. N and L
2. Within / across of run / material.

• N = Number of control measurements involved
• L = Limit exceeded.
OR

• Within run / Across material : At one day ( within one run ) all the levels of QC
are violated.
• Across run / Within material : Same level of QC will violate but in 2 or more
consecutive runs
Date QC levels
Day 1 Level 1 Level 2 Level 3
Date QC levels

• QC lies between mean and
1SD – no particular
nomenclature
• When going beyond 2SD –
called 2S violation
• When going beyond 3SD –
called 3S violation

• 1 control exceeding the 2SD limit
• Denotes a Random error or the
beginning of a systematic error.
• Even in the absence of any
analytical errors 4.5% of data
points in the region of 1:2S region.
• It can be considered as a warning
rule.
1 : 2S Rule

• 1 run exceeding the 3SD limit
• Denotes a Random error or the
beginning of a large systematic
error.
• A run is rejected when a single
control measurement exceeds the
3SD limit.
1 : 3S Rule

• 2 consecutive QC results greater
than 2s on the same side of the
mean.
• This rule identifies systematic
error only.
• 2 application to this rule :
•With in run ( in the 2 levels
of QC in the same run )
•Across run ( in the same QC
in 2 consecutive runs )
2 : 2s Rule

• 2 levels of control material with
4SD difference between the 2 data
points.
• Denotes a random error only.
R : 4s Rule

• 4 consecutive QC results greater
than 1s on the same side of the
mean.
error only.
• 2 application to this rule :
•With in run
•Across run
4 : 1s Rule

• 10 consecutive QC results for one
level of control are on the side of
the mean or both levels of control
have five consecutive results are
on the same side of the mean.
error.
•There are 6x, 8x, 10x, 12x
violations. All denotes systematic
errors.
10x Rule

Rule Violation Systematic error Random error
1:2s  
1:3s  
2:2s  -
4:1s  -
10x  -
R:4s - 

 It implies critical supervision of all aspects of laboratory tests.
 Also includes maintenance and control of equipments and apparatus
 It is necessary for correct interpretation of test results, for the lab to
establish normal reference values that are valid for their test methods.
PROFICIENCY SURVEILLANCE

 Should have instruction manuals regarding proper use and
maintenance.
 Should be monitored and recorded for quality control procedures,
function checks.
 Date of last and next due maintenance as well as calibrations must
be clearly mentioned in the machine records.
QC - EQUIPMENT

• Either done in laboratory using calibrator materials
or done at the manufacturing site and a verification is done in
laboratory.
• Caibrator materials are specific.
CALIBRATION

• with a new instrument.
• when a specified time period is elapsed.
• when an instrument has had a shock or vibration which potentially
may have put it out of calibration.
• whenever observations appear questionable.
Need for calibration

 To implement a QC program…
 Establish written policies and procedures
 Assign responsibility for monitoring and reviewing
 Train staff
 Obtain control material
 Collect QC data
 Set target values
 Establish LJ chart
 Routinely plot control data
 Establish and implement troubleshooting and corrective action
protocols
 Establish and maintain system for documentation.

 Post-examination components
 Reviewing patient results
 Posting patient results
 Maintaining patient records
 Monitoring turnaround time
 Administering and reviewing customer
 Satisfaction surveys
 Documenting maintenance

 LABORATORY QUALITY SYSTEM DOCUMENTS
 Quality manual
 Safety manual
 Policies, procedures and processes
 Management records
 Technical records
 Customer care and query / complaint resolution records.

Quality control.pptx

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Quality control.pptx