Introduction to QA and QC

8/13/2019 Introduction to QA and QC

1/56

INTRODUCTION TO QUALITY CONTROL &QUALITY ASSURANCE


2/56


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


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


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


6/56

QA involves monitoring:

The process of monitoring instruments

Reagents

Test procedures

Technologist performance

The accuracy of reported results


7/56

QUALITY CONTROL

It involves the control of errors in the

performance of tests and verification of

test results.

QC should :

PracticalAchievable

Affordable


8/56

QC monitors the performance of any analytical

system.

Analytical system consists :

Instruments

Reagents

Calibrators

ControlsSamples

Operator technique(SOPS)


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


10/56


11/56


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.


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.


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


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


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


17/56


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


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


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)


21/56

It varied from instrument to

instrument.

What is the advantage of using

assayed commercial controls?


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


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)


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 .


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


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


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.


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


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


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


31/56

Gaussian Distribution Curve:


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


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.


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


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.


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


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


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


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


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.


41/56

TREND


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.


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.


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.


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


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


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.


48/56

REPORTING PATIENT RESULTS

Patient results can be reported if the values are

IN-CONTROL


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


50/56

THE VARIABLES IN THE QA

Pre-analytical variables

Analytical variables

Post-analytical variables


51/56


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


53/56


54/56

SYSTEMIC ERROR

Deteriorated reagents

Mechanical trouble in the instrument

Peculiarity in worker methodology

eg; incorrect pipetting


55/56

POST ANALYTICAL

Errors which occur after the test procedure:


56/56

TERMINOLGYFind the meaning of the following according to QA& QC:

PopulationSampleParameterStatisticMaximum valueRangeThe meanMedianModeMinimum value.

Introduction to QA and QC

Documents

Transcript of Introduction to QA and QC