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47
| 1 | 2008
Klinisk Biokemi i Norden
up to 1,000 µmol/l, with hemoglobin up to 1 g/l, of
triglycerides up to 2.3 mmol/l and with ascorbic acid
up to 1,700 µmol/l [2]. Since there are no common
international reference materials for myoglobin, the
calibrators are standardized against in-house and
commercially available reference materials [4].
Samples
EDTA-plasma routine patient samples and Konelab™
Myoglobin Control sera Low and High were used as
sample materials for the study. The surplus patient
plasma samples were collected based on their
CK-MBmass and troponin T values [3].
Results
The detection and determination limits of the
Konelab™ myoglobin application were 6.4 µg/l and
12.8 µg/l, respectively. They were calculated from
20 replicate measurements of 0.9% NaCl (detection
limit: mean+2*SD, determination limit: 2*detection
limit).
The linearity of the Konelab™ myoglobin applica-
tion was determined from a manual dilution series
(n=6) of an EDTA-plasma sample with 0.9 % NaCl
with an original myoglobin concentration of 488
µg/l, showing good linearity from 488 to 44 µg/l (Y
= 0.9888X + 0.5473, r= 0.999). The instrument was
capable of diluting samples up to 2,600 µg/l and no
hook effect was evident with myoglobin concentra-
tions tested up to 10,718 µg/l (with direct measure-
ment 9,760 µg/l). Parallel measurements using 108
plasma samples with myoglobin values up to 488 µg/l
showed a mean difference of 0.03 % (Y = 0.999 * X –
0.078, r = 0.999). The results with control samples at
normal and elevated concentrations showed excellent
agreement with the expected mean values (values not
shown).
Within-run and between-day imprecisions were
calculated using NCCLS Document EP5A as a guide-
line, and control sera and pooled plasma as sam-
ples (Table I). Within-run variation was calculated
from 24 replicate measurements of control sera and
plasma. Between-day variation was calculated from
11 measurements over two weeks. The total varia-
tions of the control samples were 4.11 and 2.14 %,
respectively.
The Konelab™ myoglobin application was com-
pared to the Roche Myoglobin Elecsys® STAT-test
(Figure 1). 77 samples were within acceptable meas-
uring range (below 154 µg/l with Konelab™) and used
for comparison of the methods: Elecsys® = 1.179 *
Konelab™ - 1.128, r = 0.947.
Table I
The within series and between series variation on the new myoglobin method on a Konelab™ 20XTi analyzer.The analyses have
been performed for low and high control lots and six different plasma pools.
Within series of variation (%)
Low control
High control
Plasma 1
Plasma 2
Plasma 3
No.
24
24
24
24
24
Mean
64,85
233,21
60,14
88,73
218,3
SD
1,66
2,34
1,97
1,8
2
CV%
2,56
1
3,28
2,03
0,92
Between series of variation (%)
Low control
High control
Plasma 4
Plasma 5
Plasma 6
No.
11
11
11
11
11
Mean
60,24
230,3
158,13
217,7
512,2
SD
2,16
4,35
5,36
3,2
9,27
CV%
3,21
1,89
3,39
1,47
1,81
(Fortsætter side 48)
