IFCC Primary Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes at 37°C. Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes

Abstract

This paper is the first in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and with the certification of reference preparations. Other parts deal with: 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 fication of Four Reference Materials for the Determination of Enzymatic Activity of y-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary reference values is also in preparation.

Defining and measuring biological activity: applying the principles of metrology

“…This is particularly so for proteins because of the multiple functions that a single protein frequently expresses, and also because of the presence in the biological sample of different proteins that nominally express the same or a similar function. A practical but limited solution to this problem has been achieved for the measurement of enzymatic activity under highly optimized and rigidly defined conditions, a solution that designates enzymatic activity measurements as catalytic activity concentrations and procedure-defined measurands [6] x . The ''procedure-defined measurand'' approach does not lend itself to the acquisition of new information about the function of the measurand and does not address the challenge that originates from the need for translating genotype to phenotype at the level of the molecule and its structure.…”

“…The rigorous application of these principles and tools to the measurement of biological activity has been limited to small molecules and ''procedure-defined measurands'' x , e.g., enzymes [6]. We believe that these principles can be applied generally to the measurement of other biological entities, including macromolecules, and can be directly related to their activity in biological systems.…”

“…An additional, and possibly the greatest, advantage of this definition is that the variable f can be interpreted using contemporary knowledge of biochemical reaction mechanisms 6 . In fact, it is the ability to interpret f mechanistically that makes it useful for harmonizing the biological and 5 An idealized macromolecule might be considered to be analogous to an ideal gas, but the focus is on the structural uniformity of the chemical species, rather than the absence of intermolecular interaction.…”

“…Such complex mixture reference materials are susceptible to ''matrix effects'' that go unrecognized and change upon replacement of the original reference material with replacement batches (see commutability, above). (x) Procedure-defined measurand [6]: a measurand for which the chemical specification included in c and the property f in the proposed equation are combined. Specifications for the conditions and concentrations of reactants and effectors under which the measurement procedure is performed are comprehensively determined to obtain comparability and traceability of the measured value.…”

Metrological traceability – a concept for standardization in laboratory medicine

“…Instead, the enzyme measurand has to be defined by an exactly described conventional reference measurement procedure. This concept is described in ISO 18153 [ 3 ] and the respective primary reference measurement procedures have been published by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) for a series of enzymes [ 4 ].…”