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16
| 2 | 2003
Klinisk Biokemi i Norden
Discussion
Potassium
Table 2: Serum and plasma potassium reference inter-
vals from different sources
The upper reference limit for serum potassium is mar-
kedly lower than Tietz and Laurell suggests, but this is
not the case for plasma. As the lower reference limit is
essentially the same for serum and plasma for NORIP,
Tietz and Laurell, but not the upper limit, this differen-
ce probably have something to do with sample treat-
ment after collection. It might be assumed that sample
treatment have been optimal in this project (see
“Sample collection”) relative to what is common in
general practice.
Creatinin
Plots of the creatinin reference value distributions for
male and female for the three major method groups
Jaffé, Vitros (Ortho) and enzymatic are shown on the
project home site.
Enzymes
See (7).
Documentation
Results from the project have been continuously
updated on the project home site (1). Specific details
for each property can be viewed by selecting the spe-
cific property from the table presented by selecting
“Preliminary project data” and "Compiled data for each
component".
Implementation of common reference intervals
Validation of method
To use the common reference intervals in Nordic
laboratories the NORIP project group suggests that
the quality goal should be that the laboratory’s
absolute value of bias relative to target value for the
control X (or CAL) should be less than 0.375 of total
biological variation, i.e. |M/T – 1|<B where M is the
measured value of X (or CAL) in the laboratory, T is
the CAL target value and B the bias quality goal. B
is presented in table 1 for each component in the
column “Quality goal”.
For the enzymes and some other components
with low target values for CAL and X it might be
necessary also to validate the method with respect
to trueness at the levels of the reference limits.
On the project home site comparisons between
serum and plasma for different instruments/instru-
ment manufacturers are presented. These compari-
sons should be taken into account before reference
intervals for plasma are taken into use.
The control serum X (NFKK Reference Serum X)
will be available from DEKS
3
.
NOBIDA
(Nordisk Reference Interval Projekts Biobank og database)
The intention with establishing the bio-bank is to let
other projects use the samples for establishing Nordic
reference intervals for other properties than described
here. NFKK has established a group that on their
behalf will have the responsibility to handle requests
for data and samples from the NFKK data- and bio-
bank NOBIDA. The leader for the group is Pål Rustad.
Guidelines for requests will soon be published on the
internet home site of NORIP and at the NFKK home
site (http://nc.ibk.liu.se/nfkk/head.htm).
The bio-bank including the control X, is located
at DEKS.
NORIP Tietz (5)
Laurell (6)
Serum 3.5-4.6 3.5-5.1
3.5-5.0
Plasma
3.4-4.4 3.4-4.4
3.5-4.5
Female
Male
Reference
90% confidence
N Reference
90% confidence N
interval
interval
interval
interval
Enzymatic
46-92
41-50, 86-96 137 60-105
57-64, 101-109 113
Jaffé
52-84
51-53, 83-87 944 64-98
62-65, 96-100 858
Vitros
50-81
49-52, 79-83 298 64-102
63-66, 99-105 259
NORIP
suggestion
50-90
60-100
Table 3: Creatinin reference intervals with 90%
confidence limits for the three method groups.
3 Danish Institute for External Quality Assurance for Laboratories
in Health Care, Denmark (http://www.deks.dk/)
