Software Testing and Quality Assurance Software Quality Assurance.
Variable Control in Quality Assurance (2)
-
Upload
mustafa-khandgawi -
Category
Documents
-
view
221 -
download
0
Transcript of Variable Control in Quality Assurance (2)
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 1/40
Variable Control In
Quality Assurance
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 2/40
Sources, Types &
Documentation of Errors inClinical Laboratories
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 3/40
Laboratory Analysis
The goal of laboratory analysis
is to provide the reliablelaboratory data to the health-
care provider in order to assist
in clinical decision-making.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 4/40
Modern medicine relies on the provision of
accurate analytical results from the laboratory
both to confirm diagnosis and to monitor therapy.
If laboratory results are to play a proper role indiagnoses and treatment then they must be
trustworthy
Experience has shown that all analytical results are
subject to errors arising from a variety of causes It is essential that these errors be kept to a
minimum.
Laboratory Analysis
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 5/40
QA in Laboratories
The assurance of high-uality laboratory results relies
on a commitment to all aspects of the testing system!
including attention to"
1. Preanalytical factors are those factors that affect the
laboratory results due to handling of the specimensample prior to analysis.
2. The analytical phase includes verification of instrument
linearity! precision! accuracy! and overall reliability
through the use of standard materials! quality control(QC) samples! procedures! and #$ rules.
3. Postanalytical factors include timely and accurate
laboratory result reporting and other aspects that occur
after the analysis phase.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 6/40
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 7/40
Quality assurance has been defined by %&' as"
The total process whereby the uality of the laboratoryreports can be guaranteed. It has been summari(ed asthe"
Right result! at the
Right time! on the
Right specimen! from the
Right patient! ith the result interpretation !ase" on#
Correct reference data! and at the
Right price.
WH Definition
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 8/40
Quality Assessment
$efinition#uality assessment or uality
assurance )#*+ is a complete systemof creating and following procedures
and policies to aim for providing the
most reliable patient laboratory results
and to minimi(e errors in thepreanalytical! analytical! and
postanalytical phases.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 9/40
%rror, Error is the discrepancy
between the result obtained inthe testing process and its True
alue/ 0 *ccepted True alue/
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 10/40
&ources of %rror, 1eagents
, 2tandards
, Techniue
, Environment
, 2pecimen collection! handling etc., Many more
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 11/40
The importance clinical la!oratory
results,3se of clinical laboratory test results in
diagnostic decision making has become
an integral part of clinical medicine.,More than 45-657 of the most
important decisions on admission!
discharge! and medication are based onlaboratory test results.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 12/40
The impact of la!oratory errors$onseuences of lab errors! therefore! have
implications on8.9atient: unnecessary treatment.
;.<octor: failure to provide the proper
treatment.
=.$ommunity: poor healthcare service.
>.?aboratory: bad reputation.
These conseuences result in increased cost
in time! personnel effort! and often in poorpatient outcomes.Therefore minimi(ing lab
errors is a major task in lab management.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 13/40
%rrors in clinical la!oratory, *n @error@ is a deviation from accuracy or correctness.
,?aboratory errors may be defined as Aany defect fromordering tests to reporting and appropriately interpreting
resultsB., Errors in laboratory medicine occur most often in all
testing process phases )pre-analytical! analytical andpost-analytical steps+.
,It is the responsibility of the lab manager to minimi(e
lab errors occurring at any phase of the testing process.
,Monitoring and control of lab errors is therefore animportant challenge in the management of clinical labs
so as to produce reliable test results as soon as
possible and thereby achieve better lab performance.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 14/40
Sources of Error
Erroneous results are at best a nuisance: at worst! they
have potential for causing considerable harm.
Errors can be minimi(ed by careful adherence to robust!
agreed protocols at every stage of the testing process"this means a lot more than ensuring that the analysis is
performed correctly.
Errors can occur at various stages in the process"
pre-analytical! occurring outside the laboratory! analytical! occurring within the laboratory!
post-analytical! whereby a correct result is generated
but is incorrectly recorded in the patient@s record!
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 15/40
PR'C%&& P'T%T*+ %RR'R&
Test ordering
, Inappropriate test, &andwriting not legible
, %rong patients I<, 2pecial reuirements not specified
2pecimenacuisition
, Incorrect tube or container
, Incorrect patient I<, Inadeuate volume, Invalid specimen )hemolysed or diluted+, $ollected at wrong time, Improper transport conditions
,1- Preanalytical errors
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 16/40
!a" Specimen collection an# $an#lin%
* test result is no better than the uality of the specimenreceived in the laboratory.
2pecimen collection and handling procedures must beexplained to all parties involved in the processing of
specimens ) nursing personnel! physician assistants! andhealth-care professionals+ ?aboratory personnel are responsible for
for training other personnel involved in specimen collectionand transport and for communicating effectively in order tomaintain optimal uality of specimens for laboratory
testing. minimi(ing preanalytical errors based on acceptance or
rejection of the received specimens. 2ince preanalytical errors seem to make up the majority of
most laboratory test problems! proper training is an important
area to address.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 17/40
!b" Hemolysis
&emolysis is generally a preanalytical problem thatcan be avoided.
It is graded based on visible presence of hemoglobin!when greater than ;5 mg0d?! and it is often graded as
mild! moderate! or gross hemolysis. Cross hemolysis will often impact on almost every
test method due to release of intracellular constituents into the serum
)potassium! phosphates! ?<&! and *2T+ and colorimetric interference due to pigments.
Crossly hemoly(ed specimens should always berejected.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 18/40
!c" Specimen Contamination
The type of blood specimen contamination resulting from I fluids
would vary with the type of fluid being infused.
* dextrose solution )sugar+ I infusion would yield
extremely high glucose results in venous specimens
collected above or near the infusion area. Total parenteral nutrition )T9D+ fluid contains most of the
reuired daily nutrients for a person who can/t ingest food.
T9D fluid contamination in a specimen creates gross
tur!i"ity along with elevated lipid and glucose values and
potassium levels too high to be compatible with life. In specimens from a patient receiving a saline I infusion!
2odium and chloride results will be falsely elevated due to
contamination from saline I fluid.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 19/40
!#" Specimen Transport
Many chemical compounds are stable within plasma
or serum in itro for only a short time.
?evels of potassium! ammonia! lactate! bilirubin!
glucose! $'; ! sodium! urea! and alkaline
phosphatase! for example! are particularly affected
by contact with blood cells! which can continue to
undergo cellular metabolic processes after blood has
been removed from the body.
E.g. Clucose will decrease as much as 8;7 perhour if not separated from blood cells or
preserved.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 20/40
!e" Specimen Transport
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 21/40
!f" A##ities to 'loo#
3sing the wrong additives or the wrong amount ofadditive can cause adverse effects on blood specimens. 2odium oxalate! sodium fluoride! or sodium heparin cannot
be used for samples needed for sodium analysis
because they increase the level of sodium. *mmonium heparin should not be used for specimens
intended for plasma ammonia or urea testing because it adds to the chemical being measured.
2odium fluoride cannot be used for en(yme analysis samples because fluoride acts as an inhibitor to most en(yme activity.
Ethylenediaminetetra-acetic acid )E<T*+! sodium citrate! andsodium oxalate cannot be used in samples that will be usedfor mineral analysis because they remove calcium and magnesium.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 22/40
!%" Sample (reparation
2ample preparation involves processing of the
sample prior to and in preparation for analysis.
9rocessing involves centrifugation!
and making an aliuot of the specimen ina test tube or sample cup
eep in mind that clotted or whole blood cells
can affect chemicals in the sample over a
period of time! such that additional chemicals
arise or some chemicals are consumed
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 23/40
It is very difficult to establish effective methods for
monitoring and controlling preanalytical variables
because many of the variables are outside the laboratory
areas.
1euires the coordinated effort of many individuals and
hospital departments
9atient Identification
The highest freuency of errors occurs with the useof handwritten labels and reuest forms. The use of
bar code technology has significantly reduced I<
problems.
/ow To Control Preanalytical %rrors
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 24/40
2o!F"
8.Training of personnel for proper collection and
handling of samples! including adherence to
specific steps and maintaining turnaround timeinvolving sample receiving and processing.
;.3se of well-written procedures and policies can
help to minimi(e preanalytical errors )specimen
collection manual+
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 25/40
*nalytical 0easurement
, nstrument not cali!rate"
Correctly
, &pecimens mi up
, ncorrect olume of specimen
, nterfering su!stances present
, nstrument precision pro!lem
,2- *nalytical errors
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 26/40
Test interpretation
, Preious alues not aaila!lefor comparison
Test reporting
, rong patient $
, Report not legi!le
, Report "elaye"
, Transcription error
,3- Post *nalytical errors
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 27/40
Analytical ariables an# Quality Control
The ideal analytical method is accurate! precise!sensitive and specific. *ccurate" It gives a correct result
9recise" that is the same if repeated 2ensitive" It measures low concentrations of the
analyte 2pecific" is not subject to interference by other
substances
In addition! it should preferably be cheap! simple anduick to perform.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 28/40
There are many analytical variables that must becarefully controlled"
%ater uality $alibration of analytical balances $alibration of volumetric glassware and pipettes 2tability of electrical power 2tability of temperature of heating baths!
refrigerators! free(ers and centrifuges
Control of analytical aria!les
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 29/40
$ocumentation
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 30/40
, <ocumentation is a process of providingwritten information about the laboratory
testing process. There are many methods
to make documentation for yourlaboratory such as
8.&ard documentation )written information
in paper sheets+.;. 2oft documentation )computer
program+.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 31/40
, <ocumentation should include"-
8. Test procedures.
;. %ork instructions.=. 1eceiving sample and registration.
=. Test results and uality control results.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 32/40
These are also referred to as laboratory benchmanual
Important features of 2'9/s *pplica!le and aaila!le in the laboratory
where they will be used Clearly written and easy to understand and
follow ept up to "ate using appropriate
technologies
Stan#ar# peratin% (roce#ures
!S(s"
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 33/40
The 2tandard operating 9rocedure should contain the
following"
9rocedure name $linical significance 9rinciple of method 2pecimen of choice 1eagents and euipments
9rocedure 1eference values $omments 1eferences
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 34/40
)et$o# Vali#ation
Method validation should be performed
before a test procedure is placed into routine
use.
alidation may be accomplished bythoroughly testing reference materials or by
comparison of results of tests performed by
an alternative method.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 35/40
Method validation should provide evidence of
the following"
*ccuracy 9recision
2ensitivity
2pecificity
?inearity
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 36/40
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 37/40
I#eal Test
*n ideal diagnostic test would be"
8557 sensitive! giving positive results in all diseased subjects!
and also 8557 specific! giving negative results in all subjects free of disease.
Individual tests do not achieve such high standards.
Gactors that increase the specificity of a test tend to
decrease the sensitivity and vice versa.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 38/40
If it were decided to diagnose thyrotoxicosis only if theplasma free thyroxine concentration were at least =;pmol0? )the upper limit of the reference range is ;4
pmol0?+! the test would have 8557 specificity: positive results
)greater than =; pmol0?+ would only be seen inthyrotoxicosis.
'n the other hand! the test would have a lowsensitivity in that many patients with mildthyrotoxicosis would be misdiagnosed.
If a concentration of ;5 pmol0? were used! the test would be very sensitive )all those with
thyrotoxicosis would be correctly assigned+ but havelow specificity!
because many normal people would also bediagnosed as having thyrotoxicosis.
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 39/40
Linearity
The linear
range is the concentration range
over which the measured concentration is
eual to the actual concentration without
modification of the method. The wider the linear rang! the less freuent
will be specimen dilution
8/18/2019 Variable Control in Quality Assurance (2)
http://slidepdf.com/reader/full/variable-control-in-quality-assurance-2 40/40
Linearity
* uantitative analytical method is said to belinear when" the measured value from a series of sample
solutions is linearly proportional to the actualconcentration or content of the analyte )truevalue+ in the sample solutions.
The points at the upper and lower limits of theanalytic measurement range that acceptablyfit a straight line determine the linear range.