o
o
30
C, and the Nordie method at 37 C after calibration with
the BCR material (9 seetian II,2).
In conclusion, this alternative procedure is provided as a
temporary measure only, since the procedure recommended in
1.1 cannot, at present, be freely applied by all reagent sup–
pliers. The alternative procedure represents a earobination of
both a carefully studied and officially recommended method in
wide use in clinical laboratories for many years with a well–
characterized enzyme reference material. This combination has
been demonstrated to satisfy the commutability criteria of
the ECCLS Subcommittee on Enzyme Reference Materials (9) and
of the NCCLS (lO).
Other combinations may not
be
appropriate.
2.7 Minimum Lag-Phase Time
O- 30 s. With most sera no lag-phase is observed (l-7).
2.8 Minimum Measurement Time
This is highly dependent on the catalytic activity concentra–
tion in the sample and on the instrument. The only general
guideline that can be given is that the reaction should be
monitored for the time and number of data points required to
obtain an acceptable precision at the upper reference limit.
Reaction rates may remain eonstant for at least 120 and lBOs,
respecti vely, for increases of 41 0 nm absorbance around 0.325
and 0.220 per 60s (l-7). These earrespond to about 7.5 and 5
ykat / 1 (450 and 300 U/ L), respectively. At higher catalytic
activity concentrations samples should be diluted with NaCl,
150mmol / L (l-7).
2.9 Sample Volume Fraction
Serum volume fraction may be varied within the range of 0.01
to 0.25 without significant error (l).
Klinisk kemi
i
Norden 2: suppl, 1990
83
