QUALITY ASSURANCE
IN THE CLINICAL
LABORATORY
Lecture 1
Definition
• Quality assurance is the coordinate process of
providing the best possible service to the patient
and physician
• Quality assurance includes monitoring and
controlling:
• the competence of personnel,
• quality of materials,
• methods, reagents and instruments,
• and the reliable reporting of test results
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WHO Definition
• Quality assurance has been defined by WHO as:
• The total process whereby the quality of the laboratory
reports can be guaranteed.
• It has been summarized as the:
• Right result, at the
• Right time, on the
• Right specimen, from the
• Right patient,
• With the result interpretation based on,
• Correct reference data,
• and at the Right price.
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Sources of Error
• Erroneous results are at best a nuisance; at worst,
they have potential for causing considerable harm
• Errors can be minimized by:
• careful adherence to robust, agreed protocols at every
stage of the testing process
• this means a lot more than ensuring that the analysis is
performed correctly.
• Errors can occur at various stages in the process:
• pre-analytical, occurring outside the laboratory,
• analytical, occurring within the laboratory,
• post-analytical, whereby a correct result is generated but
is incorrectly recorded in the patient's record,
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Aspects of a Good Quality Assurance Program
• A good quality assurance program has three
major aspects:
Preventive activities
2. Assessment Procedures
3. Corrective actions
1.
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Preventive Activities
• Prevent errors
• Improve accuracy and precision
• They involve the following activities:
• Method selection
• Careful laboratory design
• Hiring of competent personnel
• Development of comprehensive procedure manuals
• Effective preventive maintenance programs
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Assessment Procedures
• Monitor the analytical process
• Determine the type of error
• Determine the amount of error
• Determine the change in accuracy and precision
• These activities include:
• The testing of quality control material
• Performing instrument function checks
• Participating in proficiency testing programs
• (e.g. programs of accrediting agencies)
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Corrective Actions
• Correct errors after discovery
• Communication with the users of
laboratory's services
• Review of work
• Troubleshooting of instrument problems
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Quality Assurance versus Quality Control
• Quality control involves the use of control
samples to monitor the precision and
accuracy of a test procedure
• Control sample is processed along with the
patient samples and the results are
compared
• Quality control is an important part of
quality assurance program
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Accuracy
• Accuracy is the measure of "truth" of a
result
• Accurate results reflect the "true" or correct
measure of an analyte or identification of a
substance
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Precision
• Precision is the expression of the variability of
analysis, reproducibility of a results, or an indication
of the amount of random error
• Precision is completely independent of accuracy or
truth
• A procedure can be precise, as determined by repeat
analysis, but the result can be inaccurate
• Three terms are widely used to describe the precision
of a set of replicate data:
• standard deviation;
• variance;
• coefficient of variation
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Accuracy and Precision
Good Accuracy
Good Precision
Good Precision
Only
Neither
Good precision
Nor Accuracy
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When Errors Occur ?
• Errors occur when there is a loss of
accuracy and precision
• A primary goal of quality assurance is to
reduce and detect errors or to obtain the
best possible accuracy and precision
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Types of Errors
• Mistakes jeopardize patient care and must
be detected and avoided at all times
• They are two types of errors:
• random errors
• systematic errors
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Random Errors
• Occur without prediction or regularity
• Affect precision of measurement and causes data
to be scattered more
• Random errors occur as the result of:
• Carelessness,
• when taking short cuts in procedures,
• Mislabeling specimens,
• Incorrect filing of reports,
• Reporting of wrong result to the wrong patient
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Systematic Errors
• Errors within the test system or methodology
• Affect the accuracy of results
• Causes the mean of a data set to differ from the
accepted value
• Examples include:
• Incorrect instrument calibration
• Unprecise or malfunctioning dilutors and pipettes
• Reagents that lost their activity
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Systematic Errors
• Types of systematic errors
A. proportional systematic error or bias
• It grows larger as the concentration of analyte grows
B. constant systematic error "constant bias"
• A constant amount over the entire range of the analysis
process.
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Types of Errors
The dashed line represents ideal method
performance where the test method and the
comparative method give exactly the same
results.
The bottom line shows the effect of a
proportional systematic error, where the
magnitude of the error increases as the test
result gets higher.
The top line shows the effect of a constant
systematic error, where the whole line is
shifted up and all results are high by the
same amount.
Note that these results will also be subject to the random error of the
method, therefore the actual data points would scatter about the line as
illustrated in the figure. The range of this scatter above and below the line
provides some idea of the amount of random error that is present.
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Detecting Systematic Errors
• Analyzing standard samples
• The best way to estimate the bias of an analytical method is by
analyzing standard reference materials, materials that contain one
or more analytes at well-known or certified concentration levels
• Using an independent analytical method
• The independent method should differ as much as possible from
the one under study to minimize the possibility that some common
factor in the sample has the same effect on both methods
• Performing blank determinations
• Varying the Sample Size
• As the size of a measurement increases, the effect of a constant
error decreases. Thus, constant errors can often be detected by
varying the sample size.
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Benefits of an Effective quality Assurance
Program
• Correct and timely presentation of data to the physician
• Improvement of precision and accuracy
• Early detection of mistakes
• More efficient and cost effective use of materials and
personnel
• Meeting the requirements of inspection and accreditation
agencies
• Development of accurate and concise procedures and
manuals
• Measure of productivity of personnel and instrumentation.
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Personnel, Staff Development & Quality
Assurance
• The most expensive and complex resource in any
organization is its' employees
• Choosing the appropriate individuals for the job
and managing them effectively is one of the most
difficult and powerful means available to prevent
errors in the laboratory
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Tiers of Responsibility
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Quality Assurance System: Personnel
Management
• Intralaboratory communication
• Orientation and training
• Personnel manual
• Personnel files
• Workload recording
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