from normal persons withoutmedication. Level2
is unmodified plasma from patients in stable anti–
coagulation therapy. Level 3, moderate reduced
leve!, is plasma from normal persons diluted l+l
with human albumin 5%. Leve! 4 is plasma from
normal persons with an in vitro admixture of he–
parin 0.4 to 0.8 IU/ml.
Distribution of frozen materials
The calibrators and control material are distribu–
ted from theDanish Institute for Externa! Quality
Assurance for Hospital Laboratories, abbreviated
DEKS, which is a further extension of the Com–
mittee onAnalytical Qua!ity.
The calibrators are distributed to the Danish
Jaboratories on request and the control materials
are sent 3 timesin the first half-year and 2 timesin
the last. The materials are shipped in Styrofoam
containing solid carbondioxid.
RESULTS
Steps of standardisation
The results of the extern quality assessment sche–
mes in 1992 demonstrated, that changing the ex–
pression of anticoagulation treatment from arbi–
trary units to INR values decreased the coefficient
of variation, but only from 20% to about 12%.
Furthermore it demonstrated a distinct difference
in themean values obtained by the various throm–
boplastin reagents in use (Figure l).
Figure l .
Variation of!NR values for the most used methods in
Denmark in 1992.
,.
~
Q) • .
~
~
.
INR-Values
All methods: MEAN=
2.95,
N=lOO, CV=12.2%
Pink bars: SPA, Stago France,Mean=2.74, N=35, CY=7.1%
Green bars: PT-SSI, Nycomed, Norway, Mean=2.85, N=37,
CY=l0.5%
Blue bars: Thrombotest,NycomedNorway, Mean=3.34,N=28,
CY=8.4%
Klinisk Kemi
i
Norden 3, 1999
Figure 2 shows the effect of a recalcu1ation ac–
cording to the lst. Danish ISI calibrator on a con–
tro! plasma at anticoagulation level. Using the ISI
values stated by the manufactures of the throm–
boplastin reagents the interlaboratoryvariationwas
10.9%. With the recalcu1ated ISI values, the CV
decreased to 5.1%. In spite of the remarkable ef–
fect on the interlaboratory variation the recalcula–
tion had only a small effect on the overall mean
value, w
hi
ch increased from2.18 to2.33 INR. This
effect apparently differs with the various kind of
reagents (Figure 3). The recalculation did not al–
ter the mean value of the Nycotest (Nycomed,
Figure 2.
Effect of ':ecalculation according to the Danish ISI
calibrator. INR-Results of a control plasma at
anticoagulation leve/
20 -
15 -
~
E
10 -
::J
z
o -
u
- 2.7
INR-Values
Bluebars:Manufacturers ISI-values,Mean=2.18,N=86,CY=l0.9%
Green bars: Danish ISI-Calibrator, Mean=2.33,N=52, CY=5.1
o/o
Figure 3
1be
Ell'ect
ol!M
Dilldill
ISI~-
•
UlooraloryMeoa ,......,
md
CV's
o(
a-...,._
r....
a
po11a1t
in~ ~~oenpy
l
1m
.;.:.:a-'='
LaboraloriesusiJt
Donilh
lbtJimllfttl:luRo
151-C:tllbrator
-
Il
~
lieall
N
CY%
~
l.50
l l
103 ,
2.3}
26
4.6
SPA,SO.,O
'"105
21
H o-.:
1.35
IS
4.3
'l1lntmllolc5t
1-lAI
17
9-l
U l
6
6.2
-
N.-
1." '
IJ
lLi
1.26
5
7.9
.~~~._.
..
:U
B
86
- 111.9 ;::
2.35
52
5.1
63
