9. Quality Control and Reference Values

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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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9. Quality Control and Reference Values

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