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Quality Control and referencevalues in clinical Chemistry
Abdul Rohman
Fakultas Farmasi UGMYogyakarta
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Introduction some thoughts
When evaluating laboratory results ho! do !edetermine that is normal or acce"table# $hat is%What is normal or OK?
When does a laboratory test result become&!eird' or &abnormal' # When do be becomeuncomfortable with a result?
Statistics are used to determine the lines ofnormal and acceptable.
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Introduction some thoughts
(tatistics is used to dra! &lines in the sand' for"atient s"ecimens control s"ecimens andcalibrators
)f the results are &normal' !e *re comfortableabout them and don+t !orry
,ut if they+re abnormal !e+re uncomfortable and!e fear that there is something !rong !ith the"atient
or -ust as bad something is !rong !ith the test"rocedure .
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Key Terms in statistics and quality control
Accuracy/
Control s"ecimen/ 0is"ersion
1istogram
2recision
Quality Assurance
Quality Control
Random error
Reference method
(hift/
(tandard s"ecimen
$rend/
(tandard 0eviation 3(04/
Coe5cient of 6ariation 3C64/
Mean/
Average/
Mode/ Median/
Gaussian Curve/
2re 7 analytic 3error4
Analytical error
2ost 7 analytic 3error4 Range/
8 9 (core
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Statistical Concepts
(tatistics is a (science of ) branch of mathematics that collectsanaly:es summari:es and "resents information about&observations.'
)n the clinical lab these &observations' are usually numerical testresults
A statistical analysis of lab test data can hel" us to de;ne normalranges for "atient+s 3 normal and abnormal 4 and acce"table rangesfor control s"ecimens 3 &in' and &out' of control 4
escripti!e statistics< information about one grou" ofobservation
"nferential statistics < !ays to com"are di=erent grou"s ofobservations
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Commonescripti!e techniques Mean 9 Average value
Median9 Middle observation
Mode - Most fre>uent observation
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Commonescripti!e techniques
Mean 9 Average value
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T h e s u m o f a l l t h e o b s e r v a t i o n s
t h e n u m b e r o f o b s e r v a t i o n s
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Commonescripti!e techniques Median9 Middle observation
?ist all the observations in order ofmagnitude and "ick
the observation that+s in the middle
)n a odd @ of observations Middle
observation
)n an even @ of observations Average ofthe B middle values
Mode - Most fre>uent observation$he observation that occurs mostfre>uently )l :F
Beorge C 105 mg>)l
Beorges gl%cose al%e was 0.2 :F elow the mean
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,sta&lishment o% $e%erence $anges
Factors a=ecting reference ranges
Age (eD 0iet Medications 2hysical activity
2regnancy 2ersonal habits 3 smoking alcohol 4 Geogra"hic location 3 altitude 4 ,ody !eight
?aboratory instrumentation 3 methodologies 4 ?aboratory reagents
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An ,3ample o% the Standard Deviation to determine patient re%erence range4
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$ minim%m o 20 oserations sho%l) e sample) in or)er to otain ali)
res%lts * %t !ll %se %st 6 to sae time +
@ets )etermine the normal range or asting plasma gl%cose %sing 6 people=
Gohns gl%cose C 98 mg>)l $erage C 109 mg>)l
Ea%ls gl%cose C 100 mg>)l :F C 20.0 mg>)l
Beorges gl%cose C 105 mg>)l 2 :F C 40.0 mg>)l
&ingos gl%cose C 150 mg>)l
'ic(s gl%cose C 102 mg>)l
-rics gl%cose C 101 mg>)l
That means that the normal range or this gro%p is rom 109 H 40 or 69 149
which is H 2.0 :F rom the mean
&ingo is consi)ere) anormal i we %se this commonly accepte) criteria to )eine normal an) anormal
Iy the way the #, or this gro%p o oserations is ao%t 18J a airly ig )ispersal ao%t the mean
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