Norway), but only of the three other reagents in
use, SPA from Stago in France, Thrombotest and
Normotest both produced by Nycomed, Norway.
The same picture was seen by using a control
plasma at the moderate reduced leve!, where the
overall interlaboratory variation decreased from
8.0% to 4.8% (Figure 4).
The first steps of standardisation in Denmark
were found to have apositive effeet on eaeh of the
three eontrol levels, normal leve!, moderate redu–
ced leve! and the anticoagulation level. Thechange
from arbitrary units to INR values reduced the
variation from between 17 and 24% to about 12%
Figure 4.
Effect of recalculation according to the Danish ISI
calibrator. INR-Resultsofa controlplasma at
moderate
reduced leve!.
.·-- - ·== -
·--·
-90
y
l,l
,,.
1,1
INR-Values
Blue bars: Manufacturers ISI-values, Mean=1.22, N=90,
CV=8.0%
Green bars:Danish ISI-Calibrator, Mean=l.27, N=45,
CV=4.8%
using the ISI values stated bymanufactores of the
thromboplastin reagents. Introduetion of the Da–
nish ISI calibrator further more redueed theCV to
the leve! 5-7% (Figure 5).
Figure 5.
Effect ofstandardisalian on the interlaboratory varia–
tion for contra! plasmas at three leve/s.
=~---
20
i
o
l
~
15 1
10
l
5
o .
. ............
64
·-----,
l
The initiative of replacing the different com–
mereial and local preparations of normal plasma
pools with the Danish normal plasma ealibrator
did not havemuch effect on the INR values. This
rnight not be surprising as the local calculated ISI
value already is adjusted by the usedmean normal
prothrombin time. Only the interlaboratory varia–
tion of the prothrombin time expressed in arbitra–
ry units was redueed from the leve! 17-24% to
about 12%.
TestingoftheDanishmodelin the othersNordie
Countries
Themode! of theDanish standardisation has been
tested in all the Nordie Countries. In November
1993 the Danish Committee invited the Nordie
laboratories to participare in an extern quality ass–
essment scheme with ineorporation of the Danish
calibrators.
One hundred and thirty-one laboratories from
Norway, Sweden, Finland, leeland and Denmark
agreed to participare in the survey. The reagents in
use reflected thedistribution observed inDenmark
and the results of the scheme confirmed the effect
of this mode! of ealibration.
Figure 6 and 7 shows the distributions of the
Figure 6.
Scandinavian EQAS, !NR values offrozen controlplas–
ma with /Sl-values stated
by
themanufacturersoftest
kits.
Q;
~ 10 +-------~--lir-r••-----------------1
==
z
.
Stago
.
Nycotest
INR-Values
Thrombotest
80ther
All methods: Mean=2.34 INR, N=l30, CV=l0.5%
Klinisk Kemi
i
Norden 3,
J
999
