We recommend that the sample volume fraction should remain
within the limits specified in Table 2. Purtherrnere it must
be remembered that any predilution of sample amounts to a
major alteration of the sample volume fraction. The user
should be aware that the dilution curves of human serum will
be non-linear in several cases .
The sample volume fraction effects may vary for individual
sera, and the values in Table 2 actually represent "the worst
case". Sample volume fractions between 0.02 and 0.08 will lie
within the
±
5% variation specified in 2.1 provided no other
changes from the reaction conditions in Table l are made. (3,
5b-c, 11, 14, 21, 26).
Table 2
Serum Volume
Fraction
0.01 0.02 0.04 0.08 0.09 0.22 0.25
Relative
Reaction Rate 1.10 1.05 1.00 0.95 0.90 0.80 0.70
3. REACTION BLANK RATES
3.1 Reagent Blank Rates
A reagent blank reaction rate higher than an absorbance in–
crease at 340 nm of 0.001 per 60 s is considered unacceptab–
le. In routine practice correction for reagent blank rate is
therefore unnecessary.
3.2 Sample Blank Rates
A sample blank rate may be eaused by adenylate kinase, which
catalyzes the reversible reaction of ADP to ATP and AMP. AK
in serum may come from the
follow~ng
sources:
erythrocytes, skeletal muscle, thrombocytes, and liver cells
(2b,5b, 14, 18, 32, 33). The IFCC CK Reference Method descri–
bes the efficiency of the AK inhioitor combination of AMP,
5
Klinisk kemi
i
Norden 2: supp/, 1990
27
