QC in the Lab.pps

7/30/2019 QC in the Lab.pps

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Quality Controlin the

Pathology Laboratory

John Santangelo


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Quality Assurance

and

Quality Control


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Quality assurance in pathology

and laboratory medicine is the

practice of assessing

performance in all steps of thelaboratory testing cycle.

including pre-analytic, analytic,and post-analytic phases.


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Quality control is an integral

component of quality assurance andis the sum of processes and

techniques to --

detect, reduce, and correct

deficiencies in an analytical process.

e.g. designing new and bettermethods for analysing blood or

serum.


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Quality improvement is the practice of continuously

assessing and adjusting performance using statistically

and scientifically accepted procedures.

Preventive Maintenance of Equipment

Continual monitoring of the temperature of water baths

and refrigerators is important to the maintenance of

reagent quality and test performance.

Equipment such as microscopes, centrifuges, and

spectrophotometers should be cleaned and checked

for accuracy on a regular schedule.

Failure to monitor equipment regularly can produce

inaccurate test results and lead to expensive repairs.


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Factors in Quality AssuranceTo guarantee the highest quality patient care through laboratory testing, a

variety ofpre-analytical, analytical and post-analytical factors in addition to

analytical data must be considered.

Pre-analytical, analytical and post-analytical factors are all part of Quality

Control

Non-analytical factors that support quality testing include the following:

Qualified Personnel

Established laboratory policies

The laboratory procedure manual

Proper procedures for specimen collection and storage

Preventive maintenance of equipment

Appropriate methodology

Established quality assurance techniques

Accuracy in reporting results


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Pre Analytical

Proper Procedures for Specimen Collection and Storage

Strict adherence to correct procedures for specimen collectionand storage is critical to the accuracy of any test.

Pre-analytical errors are the most common

source of laboratory error.

The correct patient identification is critical.

Date of Birth. (careful with overseas people as Month & daymight be reversed)

Ask patient to spell their name.


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Pre Analytical (cont)

Each blood specimen obtained should be labeled with the

patients first and last name, hospital identification number,patient location, time, date and the phlebotomists initials.

Correct storage of specimens is critical to obtaining accurateresults.

Some specimens are stored at room temperature and somein the refrigerator.

Specimen integrity is an important issue when blood iscollected at a site away from the testing facility.

Blood must be centrifuged within 30 minutes ofcollection.

Delayed centrifugation will result in wrong results.


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Specimens are to be transported to the laboratory in the

appropriate containers, e.g. coolers.

Physiologic Factors Affecting Test Results

Posture- Changing from a supine to a sitting or standingposition results in a shift of body water from inside the blood

vessels to the interstitial spaces.

Larger molecules cannot filter into the tissues and concentratein the blood. There will be significant increases in test values

for lipids, enzymes and proteins.


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Diurnal Rhythm- Diurnal pertains to daylight, and diurnal

rhythm refers to the daily body fluctuations that occur.

Certain hormone levels such as cortisol and adenocorticotropichormones, decrease in the afternoon.

Other test values, such as iron and eosinophils, increase in the

afternoon.


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Exercise- muscle activity elevates creatinine, protein, creatine

kinase, aspartate transaminase, and lactate dehydrogenase

values.

Research also suggests that exercise activates coagulation

and fibrinolysis and increase platelet counts.

Stress- Anxiety can cause temporary increase in white blood

cells, catecholamines as well as an acid-base imbalance.


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Dieting- Fasting means no food or beverages except

water for 8-12 hours prior to blood collection.

If a patient has recently eaten, there will be atemporary increase in glucose and lipid content in the

blood.

As a result, the serum or plasma may appear cloudyor turbid, which interferes with testing, especially with

tests such as glucose, sodium, and complete blood

counts.


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Smoking- Patients who smoke prior to blood collection mayhave increased WBC counts and cortisol levels.

Long-term smoking can lead to decreased pulmonary function

and result in increased hemoglobin levels. (secondarypolycythaemia)


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Analytical

Appropriate Methodology

When new methods are introduced, it is important to

check the procedure for accuracy and variability.

Replicate analyses using control specimens are

recommended to check for accuracy and to eliminate

factors such as day-to-day variability, reagent

variability and differences between technologists.


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Analytical (cont)

Established Quality Assurance Techniques

Each procedure should have an established protocol toassure the quality of the results.

Usually, the normal and abnormal control samples are

analyzed at the same time patient specimens are analyzed.

Established limits of acceptable performance must bedetermined for each type of test.

If control results are not within acceptable limits, patient

results cannot be guaranteed to be accurate.

In these cases, the source of error must be identified and the

entire test repeated before a patients result can be reported.


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Analytical (cont)

Accuracy in Reporting Results

When extremely abnormal results or differences from

previous test values are found, the laboratory

protocol should establish the method of rechecking

and reporting such results.


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Things that go wrong during analysis

1. Equipment faults

2. Reagents expired

3. Reagents contaminated

4. Reagents not stored under the right conditions

5. Temperatures not checked

6. Automatic pipettes not maintained

7. Dirty glassware

8. Bad operator technique


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Qualified Personnel

The entry-level examination competencies of all certifiedpersons in hematology must be validated. Validationtakes in form of both external certification and newemployee orientation to the work environment.Continuing competency is equally important.

Established Laboratory Policies Laboratory policies should be included in the laboratory

reference manual that is available to all hospitalpersonnel.

The Laboratory Procedure Manual

Laboratory procedures should be included in the manual.


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Batch:

A batch or lot is a collection of products all identical in size,

type, conditions and time of production.

All controls have a Batch Number and expiry date so that a

fault can be traced easily.

The number of tests between controls.

Drift:

The control results are steadily increasing or decreasing away

from the true published mean value found in the packageinsert.


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Interference:

Something outside or inside the autoanalyser causing

unreliable control and test results.e.g. electrical interference, a light source losing brilliance, dirt or

dust etc. Insects.

Interpolation:

Someone changing a test or control result because it doesnt

look or feel right.

Random error:

An unexpected and unacceptable test or control result whichdisappears when repeated.

Fibrin blocking the autoanalyser.


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Standard Deviation: (SD)Any control results greater than 2 standard deviation are

flagged and the analyser usually stops.

Calibrator: (standard):

A know value supplied in the package insert to calculate the

unknown value.


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Controls:

There are Internal and External controls.

Internal controls are reconstituted and assayed.The values are given in the insert package.

External controls are sent from an outside national or

international laboratory.

The results are not supplied until after they receive your results.

This way cheating is eliminated.

Controls above and below normal reference ranges should be

performed.

Important when monitoring therapeutic Drugs.


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Bias:

Bias is a problem and is widespread when doing internal controls.

This is why external controls are done in parallel.

Examples of bias:

1. All controls should be done with the normal run, not separately and not in

duplicate.

Often the laboratory staff will do controls separately and several times until

they get the answer they want. This is incorrect and cheating.

Controls are run to detect problems with equipment and technique.

2. Large batches should have a control about every 10 to 15 samples not at

the beginning and end of a sample run.

3. The external and internal controls should not be tested separately or in

triplicate.

4. Cheating.


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NATA

National Association of Testing Authority

RCPA

Royal College of Pathologists of Australia

QAP

Quality Assurance Programs

Organizations and programs that monitor

Laboratories


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Book are kept to monitor refrigerator temperatures, water

baths, autoclaves etc, and faults that occur and how they

were rectified.

This is required by NATA.

NATA inspections are done about every three years.

Any problems have to be fixed before NATA gives approval to

continue to operate as a laboratory.

Many laboratories have been closed down for not complying

with the standards required by NATA.


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Conclusion (Quality Assurance QA)

QA is the sum of all those activities in which the

laboratory is engaged to ensure that informationgenerated by laboratory is correct.

QA includes all aspects of laboratory activities that

affects the results produced, from the choice of

methods, to the education of personnel, to the

handling of specimens and reporting results.

The real purpose of QA activities is to determine how

correct or incorrect the results coming from the labare, and to allow those managing the lab to determine

whether or not the lab is fulfilling its functions

satisfactorily.


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3 major activities of QA :

1) Preventive those activities that are done prior to the

examination of the specimen or sample and that are intendedto establish systems conducive to accuracy testing ( eg :

preventive maintenance and calibration of instruments, testing

of media, orientation and training of personnel )

2) Assessment those activities that are done during testingto determine whether the test systems are performing correctly

( eg : the use of standard and controls, maintenance of control

charts )

3) Corrective those activities that are done, when error isdetected, to correct the system ( eg : equipment

troubleshooting, recalibration of instruments )


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QA in Haematology Laboratory

QA in haematology lab is intended to ensure the reliability ofthe lab tests.

The objective is to achieve precision and accuracy

4 components of QA programme :

1) Internal Quality Control ( IQC )

2) External Quality Control ( EQC )


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Accuracy

- the closeness of the estimated value to the true value.

- can be checked by the use of reference materials which have

been assayed by independent methods of known precision

Precision

- reproducibility of a results, whether accurate or inaccurate

within a define frame time ( eg: within the same day, from week

to week etc )

- can be controlled by replicate tests, check tests on previously

measured specimens and statistical evaluation of results


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Internal Quality Control ( IQC )

Based on monitoring the Haematology tests procedures that are performed

in the lab.

includes measurements on CONTROLS & is intended to ensure that thereis continual evaluation of the reliability of the work of the lab and that

control is exercised over the release of the results.

External Quality Control ( EQC )

The objective evaluation by an outside agency of the performance by a

number of laboratories on material which is supplied specially for the

purpose.

is usually organized on a national or regional basis.

analysis of performance is retrospective.

the objective is to achieve comparability with results of other labs.


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Control materials

Specially preparedIt may be anticoagulated whole blood, preserved pooled red

cells, plasma or serum.

It can be used to check for accuracy if the value has been

reliably determined ( eg : reference centre )

Should have controls of high, normal and low values

At least 1 control specimen should be used for every batch.

If large specimens, use 1 control for every 20 specimens.


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Analysis of data

Standard deviation of control specimensDispersion of results around the mean will indicate the error of

reproducibility.

95% of results on the same specimen should be within 2 SD

and 99.7% within 3 SD.

by chance, 1 in 20 of measurement might expected to fall

outside 2 SD and only 1 in 333 outside 3 SD.

If measurement more widely dispersed, this indicates an errorin the test.


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Control Charts

Originally described by Shewhart, 1st applied in clinical chemistry by Levey

and Jennings.

Samples of the control specimen are included in every batch of patients

specimens and the results checked on a control chart.

To check precision, it is not necessary to know the exact value of the

control specimen.

Value has been determined reliably by a reference method, the same

material can be used to check accuracy or to calibrate an instrument.

If possible, controls with high, low and normal values should be used.

Advisable to use at least one control sample per batch even if the batch is

very small.

The results obtained with the control samples can be plotted on a chart.


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A minimum of 100 patients are selected to establish a


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Total = 95.4%

A minimum of 100 patients are selected to establish a

Normal Reference Range

Within 2 Standard Deviations

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QC in the Lab.pps

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