Esti ati g syste atic eo of easu eetp ocedu es of

Esti ati g syste atic e o of of lipid ua tities

easu e e t p ocedu es

Ma io a Ga ía-Pa ella, Sa ela Ga ía-Sa ta a i a, Xa ie Fue tes-A de iu* La o ato i Cli i IDIBELL-Hospital U i e sita i de Bell itge, L'Hospitalet de Llo egat Catalo ia Spai *

Co espo di g autho : Fa + E- ail: fa@ su .s s.e

S ste ati e o , also alled bias, is o e of the ost i po ta t et ologi al ha a te isti s of a easu e e t p o edu e, a d its e e tual ha ge ha e a di e t i pa t i the i te p etatio of li i al la o ato esults. A esti ato of s ste ati e o is the ea of a set of epli ate esults of easu e e t o tai ed i a o t ol o efe e e ate ial i us a t ue alue of the ua tit i te ded to e easu ed i this ate ial. As su h a t ue alue is atu e u o tai a le, i p a ti e a o e tio al t ue alue is used. The o e tio al t ue alue of the o t ol ate ial a e a assig ed alue o tai ed ith a p i a o efe e e easu e e t p o edu e , a o se sus alue o a p o edu e-defi ed alue .

To esti ate the s ste ati e o e a use a o t ol ate ial ha i g a assig ed o e tio al t ue alue. The est ethod to assig a o e tio al t ue alue is ea s of a p i a o efe e e easu e e t p o edu e, ut the easie a d heape ethod is usi g a o se sus alue esti ated i a e te al ualit assess e t s he e , . The o se sus alue is usuall esti ated as the ea o the edia , afte e o al of outlie s, of all the esults su itted i di idual pa ti ipa ts he

Page 44 eJIFCC2006Vol17No2pp044-050

easu i g the sa e pa ti ula ua tit i a gi e o t ol ate ial. A hoi e a e ade et ee th ee ki ds of o se sus alues: i the o e all o se sus alue, hi h i ludes all esults i depe de tl of the ethod of easu e e t; ii the ethod elated o se sus alue, hi h i ludes all esults o tai ed ith all easu e e t p o edu es ased i the sa e ethod of easu e e t; a d iii the easu e e t p o edu e "kit" elated o se sus alue. This hoi e should e ade depe di g o the ki d of ua tit u de easu e e t. E a ples: fo su sta e o e t atio eta olites, io s, ste oid ho o es, et . the o e all o se sus alue is ge e all used; fo atal ti o e t atio e z es the ethod elated o se sus alue is ge e all the est hoi e; a d fo a it a su sta e o e t atio tu o a ke s, peptide ho o es, et . the easu e e t p o edu e o espo di g to a pa ti ula "kit" elated o se sus alue i so e ases is the o l logi al hoi e.

The epo ts of the e te al ualit assess e t s he e RIQAS Ra do La o ato ies Ltd., UK , i the ase of lipid ua tities, ha e the th ee t pes of o e tio al t ue alues fo thei o t ol ate ials. This e te al ualit assess e t s he e is fo o e ea ; du i g this ti e, the o ga ise s se d t i e a o th t o l ophilised o t ol se a o espo di g to diffe e t lots, ut ea h lot a e epeated. Bea i g i i d this fa t, e ha e o pa ed the alues assig ed ea s of efe e e easu e e t p o edu es ith the o e all o se sus alues fo diffe e t o t ol ate ials. This o pa iso gi es i fo atio a out the diffe e es et ee the t o o e tio al t ue alues. This i fo atio ill i di ate if the use of the o e all o se sus alue is eall as good as the efe e e easu e e t alue to esti ate the s ste ati e o . We ha e e ised all the epo ts f o the e tio ed p ofi ie testi g p og a e ei ed i ou la o ato f o the ea to the p ese t i ol i g the easu e e t p o edu es fo the ua tities sho i Ta le . Du i g this pe iod the u e of li i al la o ato ies pa ti ipati g i the p ofi ie -testi g p og a os illated et ee a d . Fo ea h ua tit , data f o all epo ts ha e ee g ouped he elo gi g to the sa e lot of o t ol ate ial a d the eighed ea s ha e ee esti ated. Fi all e ha e o tai ed f o to ouples of o e tio al t ue alues. The diffe e es et ee o se sus alues a d efe e e easu e e t alues ha e ee studied usi g the li ea eg essio least s ua es odel. The pa a ete s of the eg essio li e fo ea h ua tit a d its sig ifi a e deg ee a e sho i Ta le . The e a e sig ifi a t o sta t diffe e es et ee the t o t pes of o e tio al t ue alues i holeste ol, t igl e ides a d i HDL- holeste ol, i additio , i th ee ases holeste ol, HDL- holeste ol a d apolipop otei B the e a e sig ifi a t p opo tio al diffe e es. We ha e o pa ed the t o t pes of o e tio al t ue alues usi g the Bla d-Alt a plots a d e ha e studied the elatio et ee the elati e diffe e es of the t o o e tio al t ue alues a d the efe e e easu e e t alues Figu e . It should e oted that, fo the ua tities take i to a ou t, to diffe e t o t ol ate ials ha i g si ila efe e e easu e e t alues o espo d e diffe e t elati e diffe e es. This fa t suggests that the in vitro diag osti i dust should i p o e the et ologi al


a al ti al spe ifi it of the i to a ou t.

easu e e t p o edu es used fo the ua tities take

I opi io of the Co ittee o A al ti al Qualit of IFCC , p a ti al e pe ie e has sho that the o se sus alue usuall ag ees losel ith the t ue alue i p ofi ie testi g p og a s ith a la ge u e of pa ti ipa ts ut it a ot e alid i p og a s i ol i g s all u e s of la o ato ies. Ho e e , a o di g to ou data, the use of the o se sus alue i stead of the efe e e easu e e t alue is ot app op iate to esti ate the s ste ati e o , at least fo easu e e t p o edu es elated to the ua tities i ol ed i this stud . Thus, e thi k that, he e e possi le, the esti atio of the s ste ati e o should e do e usi g a o t ol ate ial hi h ha e a o e tio al t ue alue assig ed ea s of a p i a o efe e e easu e e t p o edu e. A o di gl , e e ou age the a ufa tu e s of o t ol ate ials to assig , he e e possi le, efe e e o p i a if possi le easu e e t alues; i depe de tl of these o t ol ate ials a e "assa ed" o "u assa ed" o es. Refe e es •

•

•

•

. I te atio al O ga izatio fo Sta da dizatio . Cli i al la o ato testi g a d i it o diag osit test s ste s - I it o diag osti edi al de i es - I fo atio supplied the a ufa tu e la elli g - Pa t : Ge e al e ui e e ts a d defi itio s. ISO/CD - . Ge e a: ISO; . . Cou otte G, Va Dijk D, Va Loe e -I i g DC, Ousso e W, Va de Vat B, Visse RG, Bole N, Da J, Walke R. Sele tio , use a d i te p etatio of p ofi ie testi g PT s he es la o ato ies . http:// .eu a he .ul.pt/guides/ptguide .pdf [A essed - - ] . I te atio al Fede atio of Cli i al Che ist . Fu da e tals fo e te al ualit assess e t EQA . Guideli es fo i p o i g a al ti al ualit esta lishi g a d a agi g EQA s he es. . E a ples f o asi he ist usi g li ited esou es. /di isio s/EMD/Do u e ts/Fu da e tals-fo -EQA.pdf [A essed - - ] . Bla d JM, Alt a DG. Statisti al ethods fo assessi g ag ee e t et ee t o ethods of li i al easu e e t. La et ; : .

Ta le Pa a ete s of the eg essio li es a d thei sig ifi a e le els Qua tities S-Choleste ol; su st. . S-T igl e ids; su st. . S-Choleste ol, i HDL; su st. . S-Apolipop otei B; ass . S-Apolipop otei A ; ass .

a , - , , , ,

S = se u ; su st. . = su sta e o e t atio ; i te ept; b = slope; P = sig ifi a e le el.

P

b - , , - , - , - ,

, < , < , , , ass . =

P , , < , , ,

ass o e t atio ; a =


A o di g to ISO, IFCC a d IUPAC e o sig .

e datio s, the o

a


a is used as the de i al

d

e

f


g

h

i


j Figu e 1 Relatio et ee the elati e diffe e es of the t o o e tio al t ue alues a d the efe e e easu e e t alues a d Bla d-Alt a plots fo ea h ua tit . S = se u ; su st. . = su sta e o e t atio ; ass . = ass o e t atio . [A o di g to ISO, IFCC a d IUPAC e o e datio s, the o a is used as the de i al sig .]
