2. 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
3. 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
7. • 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
9. 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
10. 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.
11. Design a QC Program
Establish written policies and procedures
Corrective action procedures
Train all staff
Design forms
Assure complete documentation and review
12. 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.
13. 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 .
14. 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.
15. 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
16. 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).
17. 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.
20. 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
21. Qualitative QC
Quality control is performed for both,
system is somewhat different
Controls available
Blood Bank/Serology/Micro
RPR/TPHA
Dipstick technology
Pregnancy
22. 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
23. 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.
25. 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
26. 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
27. 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
29. 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.)
30. 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.
32. 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
40. 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
43. Summary
Quality Control program validates test
accuracy and reliability of investigations
used in support of optimal patient care.
44. 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/
