IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 378C

This paper is the eighth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 378C and the certification of reference preparations. Other parts deal with: Part 1. The concept of reference procedures for the measurement of catalytic activity concentrations of enzymes; Part 2. Reference procedure for the measurement of catalytic concentration of creatine kinase; Part 3. Reference procedure for the measurement of catalytic concentration of lactate dehydrogenase; Part 4. Reference procedure for the measurement of catalytic concentration of alanine aminotransferase; Part 5. Reference procedure for the measurement of catalytic concentration of aspartate aminotransferase; Part 6. Reference procedure for the measurement of catalytic concentration of g-glutamyltransferase; Part 7. Certification of four reference materials for the determination of enzymatic activity of g-glutamyltransferase, lactate dehydrogenase, alanine aminotransferase and creatine kinase at 378C. The procedure described here is deduced from the previously described 308C IFCC reference method. Differences are tabulated and commented on. Clin Chem Lab Med 2006;44:1146–55. Schumann et al.: IFCC primary reference procedures 1147 Article in press uncorrected proof Table 2 Conditions for the measurement of a-amylase. Temperature 37.08C"0.18C Wave length 405 nm "1 nm Band width F2 nm Light path 10.00 mm "0.01 mm Incubation time 60 s Delay time 180 s Measurement interval 180 s Readings (measurement points) G6 Table 1 Concentrations in the final complete reaction mixture for the measurement of a-amylase. N-2-Hydroxyethylpiperazine-N9-ethanesulfonic acid 50 mmolOl pH (378C) 7.00"0.03 4,6-Ethylidene(G1)-4-nitrophenyl(G7)-a-(1TM4)-D-maltoheptaoside 5 mmolOl Sodium chloride 70 mmolOl Calcium chloride 1 mmolOl a-Glucosidase (378C) 135 mkatOl (8100 UOl)* Volume fraction of sample 0.0323 (1:31) *Uninhibited catalytic concentration. Note: The indicated catalytic concentration of a-glucosidase shall be measured in the final complete reaction mixture if 9 gOl (154 mmolOl) sodium chloride solution is used as the sample (no inhibition by the sample matrix). Note: Besides the substances listed in Table 1, the final complete reaction mixture contains 0.1 gOl albumin, which is originally a component of Solution 3. The presence of albumin in the Reaction Solution and consequently in the final complete reaction mixture stabilizes the a-glucosidase.