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Short presentation about using internal quality control material in clinical laboratory to ensure analytical quality laboratory results for the sake of better patient care and minimizing errors in diagnosis, management, and follow up.
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Dr. Adel A. ElazabAssociate Professor of Clinical PathologyFaculty of MedicineAin Shams University, Cairo, Egypt
Internal Quality Control
Dr. Adel A. Elazab 2
Internal Quality Control
Dr. Adel A. Elazab 3
QUALITY ASSURANCEPROGRAMME
! Internal Quality Control (IQC) Procedures
! External Quality Assessment (EQA)
! Quality Management
Internal Quality Control
Dr. Adel A. Elazab 4
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
Dr. Adel A. Elazab 5
Internal Quality Control
Monitoring quality of laboratory testing, accuracy and precision of
laboratory results
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Precision and Accuracy
• Precise and Inaccurate
• Precise and Accurate
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Precision and Accuracy
• Imprecise and Inaccurate
• Imprecise and ?? Accurate
Internal Quality Control
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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
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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)
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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
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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
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1. 192 mg/dL2. 194 mg/dL3. 196 mg/dL4. 196 mg/dL5. 160 mg/dL6. 196 mg/dL
7. 200 mg/dL8. 200 mg/dL9. 202 mg/dL10.255 mg/dL11.204 mg/dL12.208 mg/dL13.212 mg/dL
Calculation of the Mean: Outliers
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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
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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
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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
ERRORSRandom 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
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Internal Quality Control
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Westgard Rules
• Allows determination of whether an analytical run s (in control) or (out of control)
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Internal Quality Control
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Internal Quality Control
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Traditional Westgard Rules
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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
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When a Rule is Violated
• Warning rule = use other rules to inspect the control points
• Rejection rule = Out of control=1. Stop testing2. Identify and correct problem3. Repeat testing on pt samples and
control4. Don’t report pt results until problem is
solved and controls indicate proper performance
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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.
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Overlap New Lot of ControlsWhen 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.
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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
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Dr. Adel A. Elazab 39
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”
YOUR VALUABLE QUESTIONS