However, for shorter measuring times catalytic activity con–
centrations up to about 15 pkat/L (900 U/L) may be measured
before dilution with NaCl, 150 rnrnol/L becomes necessary (16).
2.10 Sample Volume Fraction
With the IFCC Reference Method a linear relationship has been
documented to exist between sample volume fractions of about
0.015 to 0.08 and reaction rates and this relationship prob–
ably extends to about 0.10 (1).
Likewise, dilutions of samples with buffer or NaCl, 150
rnrnol/L do not result in significant errors (1).
3. REACTION BLANK RATES
3.1 Reagent Blank Rates
+
An LDH-2-oxoglutarate - NADH
+
H reagent blank reaction
is unavoidable.
Centamination of reagent enzymes, lactate dehydro-
genases with ALAT will cause a reagent blank rate. If reagent
blank rates are higher than 60 nkat/L (about 4 U/L) corre–
sponding to a decrease of absorbance at 340 nm of 0.002 per
60 s, the reagent should be discarded.
3.2 Sample Blank Rates
Sample blank rates rnay occur (1). In the presence of sample
+
NH
concentrations cornpatible with life up to about 1%
of
4
high glutamate dehydrogenase catalytic activity concentra-
tions may be measured. These conditions usually coincide with
highly increased ASAT and ALAT va:i.t1es, and thus may be consi–
dered cf no clinical importance.
Klinisk kemi i Norden 2: supp/, 1990
65
