Laboratory Quality Control .ppt

Quality assurance (QA)
Quality assurance (QA) refers to the planned and
systematic activities implemented in a quality system
so that quality requirements for a product or service
will be fulfilled . It is the systematic measurement,
comparison with a standard, monitoring of processes
and an associated feedback loop that confers error
prevention.
QA in Laboratory medicine is the means by which
reliability, precision and accuracy of investigations
used in support of optimal patient care can be
achieved

Quality Assessment
 Quality Assessment - quality assessment
(also known as proficiency testing) is a means
to determine the quality of the results
generated by the laboratory. Quality
assessment is a challenge to the effectiveness
of the QA and QC programs.
 Quality Assessment may be external or
internal

QC Assessment
 External QC:
 External Quality Assurance (EQAS)
 Interlab
 Internal QC
 Replicate / Split Sample
 Retained
 Recheck / Repeat Sample

Stages of Quality Assurance
 1: Pre Analytical
 2: Analytical
 3: Post Analytical

Pre-Analytical
 Decision
 Order request
 Sample collection
 Transport and
storage

• Errors made in
the period prior
to the analysis of
the sample ...
• may influence
the quality of
the final
measured
results ...
• and compromise
the diagnosis and
treatment of the
patient

Analytical
 Analysis
 Quality Control
 Maintenance &
Service

Quality Control
 Quality Control - QC refers to the measures
that must be included during each assay run
to verify that the test is working properly.
 Quality Control is the study of those error
and Procedures used to recognize and
minimize them.
 Process or system for monitoring the quality
of laboratory testing, and the accuracy and
precision of results

The QC system is designed to:
 Provide routine and consistent checks to
ensure data integrity, correctness, and
 completeness;
 Identify and address errors and omissions;
 Document and archive inventory material and
record all QC activities.

Design a QC Program
 Establish written policies and procedures
 Corrective action procedures
 Train all staff
 Design forms
 Assure complete documentation and review

QC in Medical Microbilogy Lab.
 Equipment Control:
All equipment is monitored daily to maintain
appropriate temperature (waterbaths, autoclave,
refrigerators and incubators.) Any temperature variance
outside the established range may affect the client’s
laboratory results.
 B. Media / Boichemical Control:
Media can be made in-house or purchased from media
companies .Sterlity and performance of the media is
done. If OK then the batch of media is releazed for
routine work.

 Reagent Control:
Reagents used should be tested utilizing positive and
negative controls. The quality of gram stain reagents is
checked with known bacterial cultures.
 Antimicrobial Disc Control:
All antibiotic susceptibility discs should be checked
against ATCC cultures every week and also om receipt
of antibiotics . The zone diameter of zone of inhibition
should be according to CLSI guidelines .

 Stock Culture Control:
Cultures themselves must be tested periodically to
ensure viability and performance.
 Specimen Collection and Control:
Protocols must be followed for proper collection of
client’s specimens.

Variables that affect the
quality of results
 The educational background and training of the
laboratory personnel
 The condition of the specimens
 The controls used in the test runs
 Reagents
 Equipment
 The interpretation of the results
 The transcription of results
 The reporting of results

Errors in measurement
 True value - this is an ideal concept which
cannot be achieved.
 Accepted true value - the value approximating
the true value, the difference between the two
values is negligible.
 Error - the discrepancy between the result of a
measurement and the true (or accepted true
value).

Sources of error
 Input data required - such as standards used,
calibration values, and values of physical constants.
 Inherent characteristics of the quantity being
measured - e.g. CFT and HAI titre.
 Instruments used - accuracy, repeatability.
 Observer fallibility - reading errors, blunders,
equipment selection, analysis and computation
errors.
 Environment - any external influences affecting the
measurement.
 Theory assumed - validity of mathematical methods
and approximations.

Random Errors
x
x x
x x
True x x x x
Value x x x
x x x
x
x
x

Systematic Errors
x
x x x x x x x
True x
Value

QC on the Basis of Method
 Quantitative test
 measures the amount of a substance
present
 Qualitative test
 determines whether the substance being
tested for is present or absent

Qualitative QC
 Quality control is performed for both,
system is somewhat different
 Controls available
 Blood Bank/Serology/Micro
 RPR/TPHA
 Dipstick technology
 Pregnancy

Quantative QC
 Need data set of at least 20 points,
obtained over a 30 day period
 Calculate mean, standard deviation,
coefficient of variation; determine
target ranges
 Develop Levey-Jennings charts, plot
results

Accuracy and Precision
 The degree of fluctuation in the
measurements is indicative of the
“precision” of the assay.
 The closeness of measurements to the
true value is indicative of the “accuracy”
of the assay.
 Quality Control is used to monitor both
the precision and the accuracy of the
assay in order to provide reliable
results.

Precision and Accuracy
 Precise and
inaccurate
 Precise and
accurate

Standard Deviation and
Probability
 For a set of data with a
normal distribution, a
value will fall within a
range of:
 +/- 1 SD 68.2% of the
time
 +/- 2 SD 95.5% of the
time
 +/- 3 SD 99.7% of the
time

Monitoring QC Data
 Use Levey-Jennings chart
 Plot control values each run, make
decision regarding acceptability of run
 Monitor over time to evaluate the
precision and accuracy of repeated
measurements
 Review charts at defined intervals, take
necessary action, and document

Levey-Jennings Chart
 A graphical method for displaying
control results and evaluating whether a
procedure is in-control or out-of-control
 Control values are plotted versus time
 Lines are drawn from point to point to
accent any trends, shifts, or random
excursions

Record and Evaluate the Control Values

Shewhart Control Charts
A Shewhart Control Chart depend on the
use of IQC specimens and is developed in
the following manner:-
 Put up the IQC specimen for at least 20 or
more assay runs and record down the
O.D./cut-off value or antibody titre
(whichever is applicable).
 Calculate the mean and standard deviations
(s.d.)

Shewhart Control Charts
 Make a plot with the assay run on the x-axis,
and O.D./cut-off or antibody titre on the y
axis.
 Draw the following lines across the y-axis:
mean, -3, -2, -2, 1, 2, and 3 s.d.
 Plot the O.D./cut-off obtained for the IQC
specimen for subsequent assay runs
 Major events such as changes in the batch no.
of the kit and instruments used should be
recorded on the chart.

Westgard rules
 There are six commonly used
Westgard rules of which three are
warning rules and the other three
mandatory rules.
 The violation of warning rules
should trigger a review of test
procedures, reagent performance
and equipment calibration.
 The violation of mandatory rules
should result in the rejection of
the results obtained with patients’
serum samples in that assay.
 12S rule
 13S rule
 22S rule
 R4S rule
 41S rule
 10X rule

Laboratory Quality Control .ppt

When a rule is violated
 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

Solving “out-of-control”
problems
 Policies and procedures for remedial
action
 Troubleshooting
 Alternatives to run rejection

Post Analytical
 Interpretation of data
 Data management
 Reporting
 Treatment of patient

Summary
 Quality Control program validates test
accuracy and reliability of investigations
used in support of optimal patient care.

Reference
 Text book of Medical Laboratory
Technology by Praful B. Godkar
 Hemostasis & Quality Assurance by
Manipal University
 http://www.ncbi.nlm.nih.gov/pmc/arti
cles/PMC2213906/
 http://www.westgard.com/westgard-
rules/

Laboratory Quality Control .ppt

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Laboratory Quality Control .ppt