Laboratory Internal Quality Control presentation master revision, 2014

Dr. Adel A. Elazab
Associate Professor of Clinical
Pathology
Faculty of Medicine
Ain Shams University, Cairo, Egypt

Internal Quality
Control
Dr. Adel A. Elazab 2

Internal Quality
Control
QUALITY ASSURANCE
PROGRAMME
! Internal Quality Control (IQC)
Procedures
! External Quality Assessment
(EQA)
! Quality Management

Internal Quality
Control
Internal Quality Control (IQC)
Procedures
⇒ Done during daily routine work
⇒ Provides an immediate control
⇒ Errors are corrected immediately
⇒ Routinely collect and analyze data from
every test run or procedure
Why do we need Internal Quality Control?
! Ensure that test results are reliable
! Ensure that test results are reproducible
! Control quality of daily routine work

Internal Quality
Control
Internal Quality Control
Monitoring quality of laboratory
testing, accuracy and precision of
laboratory results

Internal Quality
Control
Precision and Accuracy
• Precise and
Inaccurate
• Precise and
Accurate

Internal Quality
Control
Precision and Accuracy
• Imprecise and
Inaccurate
• Imprecise and ??
Accurate

Internal Quality
Control
Internal Quality Control
• It ensures continual check that the established
reliability of the laboratory’s work does not
fluctuate and that reports are validated before
they are released.
• It is based on monitoring the procedures which
are actually used for the tests in the laboratory.
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

Internal Quality
Control
QC Quantitative Tests
• Use 2-3 levels of controls covering the
medical decision points
• At least 20 control values over a period of
20-30 days for each level of control
• Perform statistical analysis
• Develop Levey-Jenning chart
• Run -regularly- with patient samples
• Monitor control values on chart using
Westgard rules
• Take immediate corrective action, if
needed
• Record actions taken (if any)

Internal Quality
Control
QC Quantitative Tests
• QC material must be available in
large quantities stored in small
aliquots (Ideally should last for at
least 1 year)
• Always consider as Biohazardous
• Requires very accurate
reconstitution if needed
• Always deal with and store as
recommended by manufacturer

Internal Quality
Control
Analysis of Control Materials
• Need data set of at least 20 points
obtained over 20-30 days better by
different operators in different times of day
• Calculate mean, standard deviation,
Coefficient of variation and determine
target ranges
• Develop Levey-Jenning charts
• Plot –on the chart- control values each
run/ day
• Make decisions regarding acceptability of
run using Westgard rules
• Monitor over time and at defined intervals

Internal Quality
Control
1. 192 mg/dL
2. 194 mg/dL
3. 196 mg/dL
4. 196 mg/dL
5. 160 mg/dL
6. 196 mg/dL
7. 200 mg/dL
8. 200 mg/dL
9. 202 mg/dL
10.255 mg/dL
11.204 mg/dL
12.208 mg/dL
13.212 mg/dL
Calculation of the Mean: Outliers

Internal Quality
Control
Levey-Jennings Chart
Calculate the Mean and Standard Deviation;
Record the Mean and +/- 1,2 and 3 SD Control Limits
80
85
90
95
100
105
110
115
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Day
Mean
+1SD
+2SD
+3SD
-1SD
-2SD
-3SD

Internal Quality
Control
Levey-Jennings Chart -
Record and Evaluate the Control Values
80
85
90
95
100
105
110
115
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Day
Mean
+1SD
+2SD
+3SD
-1SD
-2SD
-3SD

Internal Quality
Control

Internal Quality
Control
Findings Over Time
• Ideally should have control values clustered
around the mean (+/-2 SD) with little variation in
the upward or downward direction
• Imprecision = large amount of scatter around the
mean. Usually caused by errors in technique
• Inaccuracy = may see as a trend or a shift,
usually caused by change in the testing process
• Random error = no pattern. Usually poor
technique, malfunctioning equipment

ERRORS
Random Error (RE):
Imprecision
• Causes:
1. Pipetting error
2. Temperature error
3. Mixing defect
4. Machine need
troubleshooting
• Systematic Error
(SE): Inaccuracy
• Causes:
1. Deterioration of
control material
2. Deterioration of
calibrator
3. Deterioration of
reagents
Internal Quality
Control

Internal Quality
Control
Westgard Rules
• Allows determination of whether an
analytical run s (in control) or (out of
control)

Internal Quality
Control

Internal Quality Control Dr. Adel A. Elazab 23

Traditional Westgard Rules

Internal Quality
Control
Westgard Multirules
• When you're running 2 or 4 control
levels, use the rules:
13s/22s/R4s/41s/10x
• When you're running 3 control levels,
use a set that works for multiples of
threes:
13s/2of32s/R4s/ 31s/12x

Internal Quality
Control
When a Rule is Violated
• Warning rule = use other rules to
inspect the control points
• Rejection rule = Out of control=
1. Stop testing
2. Identify and correct problem
3. Repeat testing on pt samples and
control
4. Don’t report pt results until problem is
solved and controls indicate proper
performance

Internal Quality
Control
When a Rule is Violated
• Change one variable at a time to troubleshoot an out of control
(> ±2sd) test.
• The variables are usually common to all instruments or
procedure systems and include the following:
• 1. Try a fresh vial of QC
• 2. Try a new reagent (same lot)
• 3. Try a new consumable (water, part, solution, tubing) if
applicable.
• 4. Try a new reagent (new lot)
• 5. Recalibrate (current calibrator)
• 6. Recalibrate (new lot calibrator)
• If a system cannot be brought into control, notify
senior staff. Do not process patient samples for
the test affected.

Internal Quality
Control
Overlap New Lot of Controls
When changing to a new lot number of control
material, ideally there should be an overlap period
while the new material is being analyzed to
establish the new control limits.
In cases where the overlap period is not sufficient, it
is possible to establish the mean value for the new
control material in a short time, over say a five-day
period, or to start with the manufacturer’s values.
Then apply the previous estimate of SD to establish
the control limits.
These control limits should be temporary, until
sufficient data is collected to provide good
estimates of both the mean and SD of the new
material.

Internal Quality
Control
Establishing the Value of the Mean
for a New Lot of QC Material
• New lots of a quality control material should be
analyzed for each analyte in parallel with the lot of
control material in current use.
• Ideally, a minimum of at least 20 measurements
should be made on separate days when the
measurement system is known to be stable, based
on QC results from existing lots.
• If the desired 20 data points from 20 days are not
available, provisional values may have to be
established from data collected over fewer than 20
days.
• Possible approaches include making no more than
four control measurements per day for five different
days

Internal Quality
Control
QUALITY
“QUALTY IS NEVER AN ACCIDENT;
IT IS ALWAYS THE RESULT OF
HIGH INTETION, SINCERE
EFFORTS BY ALL, INTELLIGENT
AND SKILLFUL DIRECTION AND
EXECUTION, IT REPRESENTS THE
WISE CHOISE OF MANY
ALTERNATIVES”

Laboratory Internal Quality Control presentation master revision, 2014

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