Introduction to QA and QC
Transcript of Introduction to QA and QC
-
8/13/2019 Introduction to QA and QC
1/56
INTRODUCTION TO QUALITY CONTROL &QUALITY ASSURANCE
-
8/13/2019 Introduction to QA and QC
2/56
-
8/13/2019 Introduction to QA and QC
3/56
Definitions:
Quality assurance(QA):Refers to all the steps which is involved in the reporting
of a correct laboratory result
Quality control(QC):Refers to measures that should be included to verify a
test procedure/method
Quality assessment:Monitors the effectiveness of the QA & QC
It can be Internal or External
-
8/13/2019 Introduction to QA and QC
4/56
Factors which affect the quality of result:
The educational background of the laboratorytechnologist
Conditions of the specimens
The controls used in the testing
Reagents and Equipments
The interpretation of test results, Transcription of
results and Reporting of results
-
8/13/2019 Introduction to QA and QC
5/56
QUALITY ASSURANCE
Quality assurance-The right result at the
Right time , on the
Right specimen , from
The right patient , with the resultinterpretation based on
Correct reference data , and at the
Right price
-
8/13/2019 Introduction to QA and QC
6/56
QA involves monitoring:
The process of monitoring instruments
Reagents
Test procedures
Technologist performance
The accuracy of reported results
-
8/13/2019 Introduction to QA and QC
7/56
QUALITY CONTROL
It involves the control of errors in the
performance of tests and verification of
test results.
QC should :
PracticalAchievable
Affordable
-
8/13/2019 Introduction to QA and QC
8/56
QC monitors the performance of any analytical
system.
Analytical system consists :
Instruments
Reagents
Calibrators
ControlsSamples
Operator technique(SOPS)
-
8/13/2019 Introduction to QA and QC
9/56
ACCURACY AND PRECISIONAccuracy:
It is the ability to reproduce or realize the
true value of a population attribute.
Precision:
Precision is also a measure of performance
It is the ability to obtain the same results time
after time, on the same sample
-
8/13/2019 Introduction to QA and QC
10/56
-
8/13/2019 Introduction to QA and QC
11/56
-
8/13/2019 Introduction to QA and QC
12/56
STANDARDS AND CONTROL SERA
To validate results all the analytical
instruments should be calibrated and controls
must be run with each set of patient samplesCalibration can be accomplished either by
analyzing solutions of known compositionknown standards.
-
8/13/2019 Introduction to QA and QC
13/56
CONTROLS
It is solution that contains the same constituents
as those being analyzed in the patient sample.
It should be analyzed along with patient sample,
using the same method ,test conditions and
reagents.
A normal and an abnormal control should be run.
Each days results are used to construct a QC
record called the Levey-Jennings chart.
-
8/13/2019 Introduction to QA and QC
14/56
Control sera are available in the following
forms:1. Lypholyzed / freeze dried
2. Pre- diluted form( ready to use)
3. Ethylene-glycol- based controls ( should not be
used on analytes measured by ion-specific
electrodes). These are stored at 0 C
-
8/13/2019 Introduction to QA and QC
15/56
Standard Deviation:
68.2% chance, a control result will fallwithin +/- 1 SD
95.5% chance, a control result will fallwithin +/- 2 SD
99.7% chance, a control result will fall
within +/- 3SD
-
8/13/2019 Introduction to QA and QC
16/56
If a laboratory result fall outside the quality
control result range, it is called __________
Levey-Jennings Charts:
- Used to determine whether the method is in-
control
- Each level of control will have a differentquality control chart
-
8/13/2019 Introduction to QA and QC
17/56
-
8/13/2019 Introduction to QA and QC
18/56
STANDARD
It is a substance that has an exact known value
and that, when accurately weighed or measured
, can produce a solution of an exact
concentration
Standards can be called as reference materials
-
8/13/2019 Introduction to QA and QC
19/56
Standards:
They are used when:Calibrating an instrument in the installation
Re-calibrate after repair or according to
manual
If the analytical values are out of control
-
8/13/2019 Introduction to QA and QC
20/56
CALIBRATION
Calibrators are used to standardize machines
Calibration involves checking the performance
of machines before sample is being analyzed
and results issued.
It is process of comparing instrument response
to known physical properties such as electronic
signals(cell counters) and light spectra
(spectrophotometers)
-
8/13/2019 Introduction to QA and QC
21/56
It varied from instrument to
instrument.
What is the advantage of using
assayed commercial controls?
-
8/13/2019 Introduction to QA and QC
22/56
ERRORS AFFECTING THE RESULT:
1. Errors of scatter (imprecision )
These are irregular or random errors.
Not due to method but may be due to technique
5 /100 fall out of 2SD range.
2. Errors of bias (inaccuracy)
These are systemic error, all samples are affected
May be due to reagent deterioration/calibration
-
8/13/2019 Introduction to QA and QC
23/56
FACTORS AFFECTING QUALITY ASSURANCE
1. Specimen collection
2. Calibration and quality control
3. Instrument operation /maintenance
4. Patient result handling (interpretation and reporting
of test results)
-
8/13/2019 Introduction to QA and QC
24/56
PREVENTIVE MAINTENANCE OF EQUIPMENT
Poorly maintained analytical equipments and
instruments can affect the quality of results.
Maintenance is important to ensure effective
and efficient functioning of laboratory
equipments and instruments .
-
8/13/2019 Introduction to QA and QC
25/56
ADVANTAGES OF PPMMaintain high level of performance
Less unexpected shut down time during
operation
Lengthening instrument
Improve the technologists knowledge of how
the equipment works and how to maintain it
Lower repair costs
-
8/13/2019 Introduction to QA and QC
26/56
QUALITY CONTROL ON DIAGNOSTIC TESTPROCEDURES
A QC programme should be implemented on all
the laboratory procedures.
It is a statistical system for measuring thereproducibility of degree of precision in the
laboratory procedure.
The program ensures the physicians and
patients, quality results
-
8/13/2019 Introduction to QA and QC
27/56
STANDARD DEVIATION, VARIANCE & MEAN
STANDARD DEVIATION :is measure of the
scatter of the sample values around mean
It can be derived with the calculation of thevariance
It can be used to calculate the acceptable
variance of the given test procedure.
-
8/13/2019 Introduction to QA and QC
28/56
CALCULATING THE MEAN
By calculating the average of a set of values
Calculate the mean for the following values?
The values were obtained after repeatedanalysis for a glucose control serum:
82,85,90,81,86,94,89
-
8/13/2019 Introduction to QA and QC
29/56
Median & Mode:
Median:
Central number in the sequence of numbers
Equal amount of numbers are above andbelow the median value
Mode:
Number that occurs most frequently in a
sequence
-
8/13/2019 Introduction to QA and QC
30/56
Gaussian Distribution:
When mean, median and mode are all thesame number it is said that the numbers are
having a Gaussian Distribution or Normal
Distribution
-
8/13/2019 Introduction to QA and QC
31/56
Gaussian Distribution Curve:
-
8/13/2019 Introduction to QA and QC
32/56
Variance:
Indicates how far apart from each other, or
how precise are the number within a group.
VARIANCE(s2)= (mean-value) 2
n-1
-
8/13/2019 Introduction to QA and QC
33/56
CALCULATING THE STANDARD DEVIATION
Calculate the varianceSymbol of variance is S 2
Calculated by subtracting each value from the mean
value and taking the square of it and the sum of
which is divided by n-1
(where n is the total number of values)
STANDARD DEVIATION is calculated by taking the
root of the variance.
-
8/13/2019 Introduction to QA and QC
34/56
FORMULAR - Variance
STANDARD DEVIATION(s)=root of variance
CALCULATE THE 1S 2S and the 3S values if the s=
4.11
1s,-1s,2s,-2s,3s,-3s
-
8/13/2019 Introduction to QA and QC
35/56
CHART THE VALUES IN LEVEY JENNINGSCHART
Mark the x-axis as the concentration
Mark the y-axis control 1-10
Mark the 1s 2s and 3s respectively on the x-axisThe chart should show a fairly even distribution
of values on each side of the mean within +2SD
and -2SD.
-
8/13/2019 Introduction to QA and QC
36/56
USING THE LEVEY-JENNINGS CHART
Daily run control for each batch of samples
Chart them on a daily con t ro l char t
See if the values are within the +2SD
-
8/13/2019 Introduction to QA and QC
37/56
INTERPRETATION OF RESULTS
CONTROL VALUE WITHIN THE +2SD
It means the patient results are reliable
CONTROL VALUE OUTSIDE THE +2SD
Means that the results are un acceptable
Patient report should not be given
Run a control again and the patient sample
Still it is not falling within the 2SD range, do not
report the patient results
-
8/13/2019 Introduction to QA and QC
38/56
IDENTIFICATION OF ERRORS
Reagent deterioration or the incorrect
preparation of a working reagent.
Faulty equipmentWrong filter may be used.
Wrong method
Environmental conditions
-
8/13/2019 Introduction to QA and QC
39/56
TRENDS AND SHIFTS IN THE CHART
TREND
It is when the control value constantly increase or decrease
over a period of time. (6 to 7 days)
3-4 values are always high/low
Occurs slowly
It tell you that there is an error:
In the instrument
The technique
The reagents
-
8/13/2019 Introduction to QA and QC
40/56
SHIFT A Shift is when a majority of values fall on one sideof the mean, for a consecutive 6 to 7 days
It tell you that there is an error/systemic error
In the instrument
The technique
The reagents
TRENDS AND SHIFTS must be investigated. Run
control with a new lot number of control sera.If error persists re-calibrate your machine.
-
8/13/2019 Introduction to QA and QC
41/56
TREND
-
8/13/2019 Introduction to QA and QC
42/56
WESTGARDS RULES
It is a guideline to decide a whether amethod/procedure is out of control.
To use the guideline all laboratories should
run and normal and an abnormal control
sera.
-
8/13/2019 Introduction to QA and QC
43/56
A RUN OUT OF CONTROL1. Both controls are outside the +2SD
2. The same control level is outside the +2SD
successive runs
3. Controls in four consecutives runs have valuesgreater than +1SD all in the same direction.
4. Ten consecutive control values fall on the one side
of the mean.
-
8/13/2019 Introduction to QA and QC
44/56
Warning rule or 1 2s rule
The first number denotes the number ofquality control results.
The subscript refers to the Westgard rulethat is being violated.
Violated when either of the two controls
exceeds 2SD from the mean in a either a
positive or negative direction.
-
8/13/2019 Introduction to QA and QC
45/56
The 1 3S Rule
The 1 3s rule is violated when the result of
one of the two QC results is outside of
3SD.The result is Out of control
Repeated / ReportedDue to random error
-
8/13/2019 Introduction to QA and QC
46/56
The 2 2s Rule
If both results falls or if one results forconsecutive days falls outside 2SD range41s Rule:
One control falls on the same side of themean and exceed +/- 1SD, for fourconsecutives runs
Two control/two consecutive runs
-
8/13/2019 Introduction to QA and QC
47/56
The 10x rule:
- 10 consecutives runs ( for one QC )
results falls on the same side of the mean
- Results fall in on the same side of the
mean for both levels of control for 5 days.
-
8/13/2019 Introduction to QA and QC
48/56
REPORTING PATIENT RESULTS
Patient results can be reported if the values are
IN-CONTROL
-
8/13/2019 Introduction to QA and QC
49/56
QA- Quality Assurance
USES:
Monitoring factors that may affect the quality of
laboratory test results.
For correcting any deficiencies found during the
monitoring process
For reevaluating the system after correctionsTo inform staff of any procedural changes
-
8/13/2019 Introduction to QA and QC
50/56
THE VARIABLES IN THE QA
Pre-analytical variables
Analytical variables
Post-analytical variables
-
8/13/2019 Introduction to QA and QC
51/56
-
8/13/2019 Introduction to QA and QC
52/56
CONTROLLING THE VARIABLE:Selection of appropriate tests
Identification and preparation of the patient
Collecting and labeling of the sample
Transport of the sample to the laboratory
Proper handling of the sample from the time of collection until
the time of testing
Placement of sample in the laboratory work load
Storage of reagent used to perform tests
Periodically verifying that procedure manuals are complete
and up to date
-
8/13/2019 Introduction to QA and QC
53/56
-
8/13/2019 Introduction to QA and QC
54/56
SYSTEMIC ERROR
Deteriorated reagents
Mechanical trouble in the instrument
Peculiarity in worker methodology
eg; incorrect pipetting
-
8/13/2019 Introduction to QA and QC
55/56
POST ANALYTICAL
Errors which occur after the test procedure:
-
8/13/2019 Introduction to QA and QC
56/56
TERMINOLGYFind the meaning of the following according to QA& QC:
PopulationSampleParameterStatisticMaximum valueRangeThe meanMedianModeMinimum value.