About the "Compendium of Terminology and Nomenclature of Properties in Clinical Laboratory Sciences"

Since the publication of the ''Compendium of Terminology and Nomenclature of Properties in Clinical Laboratory Sciences'' (Silver Book) in 1995, significant development in metrological concepts and terminology has occurred. The second edition of the Silver Book [1], published in 2017 with the joint support of IFCC and IUPAC updates recommendations and technical reports for the clinical laboratory sciences. The book describes a common structure and language for a reliable exchange of person examination data. This format, developed by the IFCC-IUPAC Committee-Subcommittee on Nomenclature for Properties and Units (NPU), applies to multiple disciplines, including clinical allergology, clinical chemistry, clinical haematology, clinical immunology and blood banking, clinical microbiology, clinical pharmacology, molecular biology and genetics, reproduction and fertility, thrombosis and haemostasis, and toxicology. It is adapted both to quantitative and qualitative information (where no magnitude is involved). Concepts and rules in the communication of clinical laboratory information are explained and numerous examples are given to ensure interoperability between the various participants in clinical laboratory sciences.

Understanding the 'Silver Book' - An important reference for standardised nomenclature in clinical laboratory sciences

Clinical laboratories perform a wide menu of testing (examinations). Successful requesting, examination, and ordering in this environment requires clear standardised nomenclature. The Silver Book (SB) is an IUPAC (International Union of Pure and Applied Chemistry) publication, produced with the support of both IUPAC and the IFCC (International Federation of Clinical Chemistry and Laboratory Medicine), that makes recommendations on logical standardised nomenclature, symbols, properties, and units in many disciplines of the clinical laboratory sciences. These recommendations are founded on and in agreement with the principles and work of the International Organization for Standardization (ISO), Bureau International des Poids et Mesures (BIPM), IUPAC, and the IFCC. Practical applications described are based on those scientific principles. The SB recommendations apply to all types of examination, not only to measurement of quantities but also examination of nominal properties where no magnitude is involved. The SB is applicable not only to clinical chemistry, but to many other clinical laboratory disciplines. For examples, reports regarding haemostasis, toxicology, clinical microbiology, reproduction and fertility, clinical pharmacology, clinical allergology, clinical molecular biology, and clinical immunohaematology have been published by the IUPAC and the IFCC. Peak scientific bodies such as the IUPAC and the IFCC have important roles in the development of sound international standards for nomenclature of examinations. Such standards support safe and effective representation of patient health information, foster portability, and empower future decision support systems.

The NPU format for clinical laboratory science reports regarding properties, units, and symbols (IUPAC Technical Report)

The terminology of NPU (nomenclature for properties and units) aims at describing properties examined in clinical laboratories for a patient. It was originally jointly approved in 1966 by IUPAC and by the International Federation of Clinical Chemistry (IFCC) and covers multiple disciplines in the field of clinical laboratory sciences, including clinical allergology, clinical chemistry, clinical haematology, clinical immunology and blood banking, clinical microbiology, clinical pharmacology, molecular biology and genetics, reproduction and fertility, thrombosis and haemostasis, and toxicology. The NPU terminology adheres to international standards of metrology and of terminology, in particular the International System of Quantities (ISQ) and International System of Units (SI), the International Vocabulary of Metrology (VIM), and also to ‘An outline for a vocabulary of nominal properties and examinations – basic and general concepts and associated terms,’ recently prepared on behalf of the IFCC-IUPAC Committee-Subcommittee on Nomenclature for Properties and Units. The present document recalls the definitions of the concepts used to express a property of a patient, regarded as a system. The aim is to promote by this comprehensive summary the proper NPU terminology for reliable exchange of patient examination data. The use of this syntax and of SI units enables the translation of these descriptions into other languages without loss of meaning or accuracy. The NPU format is also well adapted for comparative and epidemiological studies. More information will be found in the upcoming 2nd edition of the Compendium of Terminology and Nomenclature of Properties in Clinical Laboratory Sciences, the IUPAC and IFCC ‘Silver Book’, and in the recently published ‘Properties and units in the clinical laboratory sciences. Part XXIII. The NPU terminology, principles, and implementation: A user’s guide (IUPAC Technical Report)’ (DOI:10.1351/PAC-REP-11-05-03).

[Recommendations for expressing uncertainty of measurement of quantitative results in laboratory medicine]

In laboratory medicine, the quantitative results of examinations are interpreted with regard to reference intervals, clinical decision limits or previous results of a patient, from which it is necessary to inform the clinician about the uncertainty of measurement linked to the value of the result. This document explains the problematic of the expression of the uncertainty of measurement. It proposes recommendations concerning a simple way to evaluate uncertainty of measurement using long term internal quality control data and the value of the uncertainty linked to the method calibration. It approaches the determination of analytical goals and the choice of methods and also the comments accompanying the record of results and a help to their interpretation.

IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C

This paper is the eighth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C 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 gamma-glutamyltransferase; Part 7. Certification of four reference materials for the determination of enzymatic activity of gamma-glutamyltransferase, lactate dehydrogenase, alanine aminotransferase and creatine kinase at 37 degrees C. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on.

Influence of human haptoglobin polymorphism on oxidative stress induced by free hemoglobin on red blood cells

BACKGROUND

An in vitro study was conducted to determine whether haptoglobin phenotypes differed in their protective effect against oxidative stress induced by extracellular hemoglobin on red blood cells.

METHODS

Conjugated dienes and thiobarbituric acid-reactive substances (TBARS) were determined in human red blood cell membranes in the presence of hemoglobin and various concentrations of each type of purified haptoglobin. In addition, the release of K+ and lactate dehydrogenase from red blood cells was measured.

RESULTS

A protective effect of haptoglobin was observed in terms of results obtained for the four parameters examined, with significant differences (p<0.001) between the three haptoglobin types; type 1-1 was the most active and type 2-2 the least active. A proportion of oxidative damage was not sensitive to haptoglobin, but to desferrioxamine (an iron chelator), indicating the participation of two actors, hemoglobin and free iron, in the oxidative stress of membrane lipids.

CONCLUSIONS

The antioxidant role of haptoglobin and the phenotype dependence were confirmed for preventing possible oxidative damage induced by free hemoglobin and iron release during its catabolism.

Intermethod calibration of alanine aminotransferase (ALT) and γ-glutamyltransferase (GGT) results: application to Fibrotest® and Actitest® scores

Two multi-component scores (Fibrotest

A reference material for traceability of aspartate aminotransferase (AST) results

Standardization of aspartate aminotransferase (AST) determination is highly desirable for inter-laboratory comparison. Serum AST mean values for 20 patients suffering from viral hepatitis showed an inter-laboratory (n=13) variation of 9.4%. Part of this variation was due to two laboratories using procedures without pyridoxal-5′-phosphate. A traceable AST value was assigned to an enzyme calibrator (EC) through the appropriate International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) primary reference procedure. The EC was commutable for seven routine methods. Common calibration using the EC reduced the inter-laboratory coefficient of variation (CV=5.9%

[Interference of hemolysis on haptoglobin determined by kinetic immunonephelometry and comparison between phenotypes]

The aim of the study was to check if a slight and non visible hemolysis to naked eye such as that induced by blood coagulation could interfere in the immunonephelometric measurement of haptoglobin, and if this interference was dependent on the protein phenotype. Results confirmed that blood coagulation induced a non visible hemolysis whose intensity markedly varied from one specimen to another. Under our conditions (kinetic measurement with a Beckman Coulter immunonephelometer), we observed with the sera a negative interference linked to the hemolysis induced by blood coagulation when compared to corresponding plasmas obtained with lithium heparinate (p < 0,005). It was checked also that this anticoagulant did not induce a positive interference. Hemolysis interference was not found phenotype dependent. These results lead us to recommend to perform haptoglobin measurements on heparinised plasmas.

[Influence of pyridoxal phosphate in measuring aminotransferases activities in patients with viral hepatitis]

Effect of a pyridoxal phosphate (PP) supplementation of reagents used for ALT and AST measurement was studied in serum of 20 patients suffering from viral hepatitis. Measurements of enzyme activities were carried out at 37 degrees C, using an automate (AU 600, Olympus). Significant differences (p < 0.0001) were observed both for ALT and AST, meanwhile they were more marked for ALT than for AST. This difference was associated with a strong interindividual variability regarding PP activation effect on ALT. In conclusion, aminotransferase measurements should be carried out with a reagent supplemented with PP, when the enzyme activity is used to evaluate a cytolysis. The same recommendation applies when ALT results are integrated into various combinations developed for the evaluation of liver status.

Determination of lipase catalytic activity in two reference materials: BCR 693 and BCR 694 by titrimetry at constant pH

Because routine assays for pancreatic lipase catalytic activity are not yet standardized, between-method comparability is very poor. This is mainly due to the lack of reference materials (RMs). The aim of this study was to assign values of catalytic concentration to two human pancreatic lipase RMs, one prepared from human pancreatic juice (BCR 693), the other obtained by recombinant technology (BCR 694). Lipase catalytic activity was assayed in five experienced laboratories, using aliquots from the same lot of triolein emulsion and a standardized titrimetric procedure, optimized with regard to substrate, cofactors and pH. The accepted sets of data (n=4) gave a mean ± the corresponding uncertainty expressed as the 0.95 confidence interval of 1732±72 U/l and 1043±60 U/l for BCR 693 and 694, respectively. Transferability of the whole operating procedure proved to be quite satisfactory. The authors conclude that both RMs can be used to verify the correct implementation of the standardized measurement procedure and to assign values to secondary lipase materials (commercial calibrators, control products) which, in turn, ensures traceability to the standardized procedure in this study, and contributes to the harmonization of laboratory results according to the Directive for in vitro Diagnostic Medical Devices.

Time-resolved fluorescence allows selective monitoring of Trp30 environmental changes in the seven-Trp-containing human pancreatic lipase

Human pancreatic lipase (HPL, triacylglycerol acylhydrolase, EC 3.1.1.3) is a carboxyl esterase which hydrolyzes insoluble emulsified triglycerides and is essential for the efficient digestion of dietary fats. Though the three-dimensional structure of this enzyme has been determined, monitoring the conformational changes that may accompany the binding of various substrates and inhibitors is still of interest. Because of its sensitivity and ease of use, fluorescence spectroscopy of the intrinsic Trp residues is ideally suited for this purpose. However, the presence of seven Trp residues spread all over the HPL structure renders the interpretation of the fluorescence changes difficult with respect to the identification and location of the conformational or environmental changes taking place at the various Trp residues. In this context, the aim of this work was to investigate the contribution of the individual Trp residues to the fluorescence properties of HPL. To this end, we analyzed the steady-state and time-resolved fluorescence parameters of five single-point mutants in which one Trp residue was substituted with a weakly fluorescent Phe residue. In addition to the Trp residues at positions 30, 86, and 252, strategically located with respect to the active site, we also mutated Trp residues at positions 17 and 402, as representative residues of the HPL N- and C-terminal domains, respectively. Taken together, our data suggested that the solvent-exposed Trp30 residue contributed to at least 44% of the overall fluorescence of wild-type HPL. Moreover, we found that the long-lived fluorescence lifetime (6.77 ns) of wild-type HPL could be specifically attributed to Trp30, a feature that enables selective monitoring of its environmental changes. Additionally, Trp residues at positions 17 and 402 strongly contributed to the 1.61 ns lifetime of HPL, while Trp residues at positions 86 and 252 contributed to the 0.29 ns lifetime.

A new continuous automated assay for the determination of intestinal lactase

BACKGROUND

A reliable, sensitive and practicable method for the measurement of intestinal lactase activity is needed.

METHOD

The assay is based on the continuous measurement of released glucose by a coupled hexokinase/glucose-6-phosphate dehydrogenase (HK/G6PDH) reagent.

RESULTS

The procedure was first optimized for lactase from rat intestinal mucosa. The optimum pH is 6.5 and apparent Km was 17 mmol/l for lactose. The procedure was also adapted on a Cobas Mira automated analyzer; progress curves of the reaction rate can be continuously monitored. The automated assay correlated strongly with the conventional method of Dahlqvist (r(2) = 0.996). The described method has also been applied to human intestinal mucosa biopsies after determination of the catalytic properties of human enzyme (optimum pH 6.0 and apparent Km 34 mmol/l).

CONCLUSION

The HK/G6PDH method is reliable, rapid, sensitive and easy to perform both manually as well as in the automated version. It is optimized for human and rat intestinal lactase.

IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. International Federation of Clinical Chemistry and Laboratory Medicine. Part 4. Reference procedure for the measurement of catalytic concentration of alanine aminotransferase

This paper is the fourth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C 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 5. Reference Procedure for the Measurement of Catalytic Concentration of Aspartate Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 2.

IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. International Federation of Clinical Chemistry and Laboratory Medicine. Part 5. Reference procedure for the measurement of catalytic concentration of aspartate aminotransferase

This paper is the fifth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C 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 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 3.

Preparation and characterization of reference materials for human pancreatic lipase: BCR 693 (from human pancreatic juice) and BCR 694 (recombinant)

There is a lack of certified reference material (CRM) for lipase catalytic activity. Consequently between-method comparability is very poor. The aim of this study was to produce two lipase CRMs, one from human pancreatic juice (BCR 693), and another using recombinant technologies (BCR 694). Lipase was purified from pancreatic juice, using column chromatography and isoelectric focusing. Recombinant lipase was produced with a transfected cell line and purified with column chromatography. Adding buffered bovine serum albumin and subsequent freeze-drying were used to stabilize both materials. A standardized titrimetric method was employed to compare their catalytic properties to those of two plasma pools of patients suffering from acute pancreatitis. About 5 kU (titrimetry, 37 degrees C) of each material were obtained. They were lyophilized without apparent modifications of their catalytic properties, which stayed identical to those exhibited by the enzyme present in patient's pools. Stability of both materials was estimated at several years when stored in a dry form at -20 degrees C. Both materials appear to have similar catalytic properties and stability and were found commutable as regards a reference method and a routine measurement procedure. An international certification campaign will be carried out to assign values to BCR 693 and BCR 694.

C-reactive protein to transthyretin ratio for the early diagnosis and follow-up of postoperative infection

The clinical usefulness of C-reactive protein (CRP) and of transthyretin (TTR) for the early diagnosis and follow-up of infection after an open fracture was prospectively investigated (cohort A). It was complemented by a retrospective study of trauma patients admitted to an intensive care unit (cohort B). Serial determinations of serum CRP and TTR concentrations were first performed in uninfected patients from cohort A to define a reference profile during the early postoperative period. It showed a concomitant increase in CRP and decrease in TTR concentrations, followed by progressive return to initial values in patients free from bacterial infection. Variations of the CRP/TTR ratio were analyzed. Recovery phase was defined by an exponential evolution of the two plasma proteins and of their ratio value. The CRP and TTR concentrations were independent of sex and severity of the trauma. In the case of postoperative infection, patients of cohort A revealed amplified CRP and TTR responses usually preceding the occurrence of clinical signs. During successful antibiotic therapy, their recovery response became superimposable to that of the reference group. The same profiles were recorded in cohort B patients admitted with lower limb fractures or various types of trauma. This suggests that observations made on cohort A can be extrapolated to othertrauma patients. We recommend that serial measurements of CRP and TTR and of their ratio should be performed every 2 days to appropriately follow-up these patients.

Evaluation of commutability of control materials

The commutability of 13 control materials was evaluated by performing parallel measurements on two different analysers: a Synchron CX-5 Delta from Beckman-Coulter and a Vitros 950 from Ortho-Clinical Diagnostics. Twenty three clinical chemistry analytes (substrates, electrolytes and enzymatic activities) were determined in plasma from 15 different patients in order to define intermethod relationship for each analyte. The relationship observed for each control material was compared to those obtained for patients' specimens. The results show that commutability depends both on the tested analyte and on the control material. No totally commutable material has been found for the whole set of tested parameters. Most control materials were commutable for inorganic phosphate, glucose, chloride, triglycerides, alanine aminotransferase, amylase and y-glutamyltransfera-se, but less than a quarter of control materials were commutable for sodium, calcium, creatinine, alkaline phosphatase and lipase. Seven materials were commutable for more than half of the analytes, whereas five control materials were commutable for less than a quarter of these analytes. We propose to verify the commutability of materials before their use in an external quality control assessement.

IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. Part 3. Reference procedure for the measurement of catalytic concentration of lactate dehydrogenase

This paper is the third in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C 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 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 gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials tamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method (1). Differences are tabulated and commented on in Appendix 1.

IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. Part 1. The concept of reference procedures for the measurement of catalytic activity concentrations of enzymes

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.

IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. Part 2. Reference procedure for the measurement of catalytic concentration of creatine kinase

This paper is the second in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C 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 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 gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of gamma-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. The pro- described 30 degrees C IFCC reference method (1). Differences are tabulated and commented on in Appendix 3.

[Enzyme calibrators: principle and practical use]

Results of catalytic activities of enzymes are highly dependent on the measurement procedures and on local conditions. Thus, only poorly marked improvement of interlaboratory comparability of results have been observed in clinical enzymology. To solve this problem, SFBC and IFCC have proposed to use "validated enzyme calibrators". Standardised operating procedures adapted to 37 C have been developed by IFCC for the most commonly used enzymes in clinical chemistry, and will be soon published. Reference materials which have been certified with these SOPs can be used as calibrators for a set of measurement methods which exhibit the same analytical specificity. Calibrators must be commutable, a property that must be checked experimentally. It is possible to produce stable and commutable materials for the calibration of a set of methods. Interest of this approach has been demonstrated for several enzymes. Results of two studies presented here show that the comparison of results to the upper limit of reference ranges does not improve the interlaboratory comparability of results in contrast to the calibration of different methods by a common calibrator which allowed to reach an interlaboratory CV close to 4% for ALT and gammaGT.

IFCC Primary Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes at 37°C. Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of γ-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase according to IFCC Reference Procedures at 37°C

This paper is the seventh in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C 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 Gamma-Glutamyltransferase. A document describing the determination of preliminary reference values is also in preparation. The certification of the catalytic activity concentrations as determined by the recently elaborated IFCC primary reference methods at 37 degrees C of four enzyme preparations, namely IRMM/IFCC 452 (gamma-glutamyltransferase), IRMM/IFCC 453 (lactate dehydrogenase 1), IRMM/IFCC 454 (alanine aminotransferase) and IRMM/IFCC 455 (creatine kinase) is described. Homogeneity data were derived from previous results. Stability was assessed using recently obtained data as well as data from previous stability studies. The collaborative study for value assignment was performed under a strict quality control scheme to ensure traceability to the primary reference method. Uncertainty of the materials was assessed in compliance with the Guide to the Expression of Uncertainty in Measurement. The certified values obtained at 37 degrees C are 1.90 microkat/l +/- 0.04 microkat/l (114.1 U/l +/- 2.4 U/l), for gamma-glutamyltransferase, 8.37 microkat/l +/- 0.12 microkat/l (502 U/l +/- 7 U/l), for lactate dehydrogenase 1, 3.09 microkat/l +/- 0.07 microkat/l (186 U/l +/- 4 U/l), for alanine aminotransferase and 1.68 microkat/l +/- 0.07 microkat/l (101 U/l +/- 4 U/l), for creatine kinase. The materials are intended for internal quality control as well as for the evaluation of test systems as required by recent European Union legislation. Furthermore, the materials can be used to transfer accuracy from a reference method to a routine procedure provided the procedures exhibit the same analytical specificity and the certified materials are commutable.

IFCC Primary Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes at 37C. Part 6. Reference Procedure for the Measurement of Catalytic Concentration of γ-Glutamyltransferase

This paper is the sixth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C 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 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 1.

[Harmonization of practices: application to the measurement of enzymatic activities used in prevention, screening, diagnosis and therapeutic monitoring]

The large metrological variation (CV, about 25%) observed between laboratories, at the national French level, for the measurement of enzymatic activities results in a loss of efficiency in using laboratory results. Current data show that the standardisation of methods is insufficient to solve this problem and needs to be completed by an harmonisation of the practices including the use of a common reference (calibrator). The present work, carried out by the joint working group between laboratories of the Centres for Periodic Health Examination and the French Society of Clinical Biology (SFBC), deals mainly with the feasibility and evaluation of the improvement of the consistency of the results. Twenty laboratories participated in this study. Five independent surveys were conducted during an height month period. Two enzymes were selected because of their clinical importance and their interest in prevention, screening, diagnosis or epidemiology: ALT (alanine aminotransferase) and GGT (gamma-glutamyltransferase). In each survey three kinds of samples i.e. control sera, candidate calibrators and human serum pools, each of them at two levels of activity (one physiological and the other pathological) were measured in duplicate. The low intra-laboratory imprecision and the high degree of the standardisation of used methods, due to an important effort previously done in this field, permitted to consider a common calibration. The stability and mainly the commutability, i.e. the ability for the candidate calibrator to show a behaviour similar to that of human samples towards the used methods, allowed to reduce the inter-laboratory variation by a half to two third-fold, reaching a coefficient of variation < 5% similar to those observed for cholesterolemia or glycemia. This level of consistency should permit to use common reference limits and common decision limits, after validation of this approach in real practice. The consequences of the harmonisation of practices, extended to the all laboratories, exceed largely the scope of this study. The reduction of the uncertainty and a better approach of the accuracy for the measurement of enzymatic activities should led to a real benefit for the patients in terms of prevention, screening, diagnosis or therapeutic monitoring and consequently for the public health.

Production and certification of an enzyme reference material for adenosine deaminase 1 (BCR 647)

BACKGROUND

We describe the preparation of a lyophilised reference material containing purified human adenosine deaminase 1 and the certification of its catalytic concentration.

METHODS

The enzyme was purified from human erythrocytes.

RESULTS

The enzyme was >99% pure on polyacrylamide gel electrophoresis. Only trace amounts (<0.4%) of alanine aminotransferase, aspartate aminotransferase and L-lactate dehydrogenase were detected in the purified fraction. The purified adenosine deaminase had a molar mass of 41600 g/mol and an isoelectric pH at 4.7, 4.85 and 5.0. The material was prepared by diluting the purified adenosine deaminase in a matrix containing 50 mmol/l Tris-HCl buffer pH 7.4 and 30 g/l human serum albumin; dispensing in vials and freeze-drying. The batch was homogeneous and the predicted loss of adenosine deaminase activity per year on the basis of accelerated degradation studies was 0.006% at -20 degrees C and 0.04% at 4 degrees C. The certified value for adenosine deaminase catalytic concentration in the reconstituted reference material is (2.55+/-0.09) microkat/l when measured by the method that uses adenosine as substrate and glutamate dehydrogenase as auxiliary enzyme at 37 degrees C.

CONCLUSIONS

The material can be used to verify the comparability of results from different laboratories, for intra-laboratory quality control, or for calibration of the adenosine deaminase catalytic concentration measurements.

[C-reactive protein and transthyretin in early diagnosis of infection after open fractures of the lower limbs (a preliminary study)]

PURPOSE OF THE STUDY

The authors investigated the value of C-reactive protein (CRP) and transthyretin (TTR) in the early diagnosis of infection after open fractures of the lower limb in an open, prospective study.

MATERIAL AND METHODS

Eighty patients were treated with acute debridement and bone fixation. Follow-up included clinical, radiological, bacteriological and biological assessment: white cell blood count (WBC), erythrocyte sedimentation rate (ESR), CRP and TTR. Diagnosis of infection was based on macroscopic presence of pus.

RESULTS

Post-operative reference biological profiles were defined in 74 cases without infection. Reference profiles of WBC and ESR showed unreliable interindividual variations and could not be considered for the diagnosis of infection. Reference profiles of CRP and TTR showed a respective increase (for CRP) and decrease (for TTR) in the early post-operative course, with return to normal values after 12 days. In 6 infected patients, CRP concentrations were suddenly increased and TTR concentrations decreased at the time (3 cases) or even before (3 cases) clinical diagnosis of infection. These variations were mostly simultaneous. No unusual profile was found. The ratio of CRP/TTR concentrations experienced also a sudden increase in infected cases.

DISCUSSION

Because of not specifical and unreliable variations in the post-operative outcome of non infected patients, WBC and ESR cannot be considered for the early diagnosis of infection. CRP and TTR concentrations with a respective cut-off value of 100 mg/L and 120 mg/L were found efficient for the early diagnosis of infection, and preceded clinical diagnosis in three of them. A CRP/TTR ratio over 60 p. 100, 8 days or more after initial surgery was found to be very specific (93 p. 100) and sensitive (100 p. 100) for the diagnosis of infection.

CONCLUSION

Serial quantifications of CRP and TTR should be performed every four days during the follow-up of open fractures in order to early diagnose a post-operative infection. Comparison of both CRP and TTR could allow a higher accuracy, because of the possible lack of variation of one the two markers.

Preparation of enzyme calibration materials

Standardisation in clinical enzymology needs not only reference methods but also reference materials. While single-enzyme reference enzymes have been developed, a multienzyme certified reference material (MECRM) available in high amount remains to be produced. To transfer trueness from the value of the reference system to patients' results, validated enzyme calibrators (EC) are also needed. Both the MECRM and the ECs must exhibit the same catalytic properties as the corresponding enzymes in human plasma. Moreover, commutability of these materials with patients' samples must be experimentally tested for one or a set of methods defined by an analytical specificity equal to that of the reference method. Various experimental studies have shown that the commutability of an enzyme material depends on the source of enzyme and its purification process, the matrix (including cofactors, effectors, additives, stabilisers... ) and the mode of processing of the final material. To promote intermethod calibration in clinical enzymology, a collaborative programme between the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) and IFCC corporate members is in progress for the development of a MECRM containing amylase, ALT, AST, ALP, CK, GGT, LDH, and lipase and exhibiting a wide and defined commutability.

A continuous automated method for the determination of intestinal disaccharidase activities

A reliable method for the measurement of various disaccharidase activities such as maltase, isomaltase and sucrase is introduced. It is based on the continuous measurement of liberated glucose by a commercially available glucose dehydrogenase reagent. The procedures were first optimized for enzymes from rat intestinal mucosa. The pH optima were similar (6.3-6.7) for the three enzymes tested, and the apparent Kms were estimated to be 18, 12 and 19 mmol/l for maltase, isomaltase and sucrase, respectively. The procedures were adapted on a Cobas Mira automated analyzer. The assays correlated strongly with the conventional method of Dahlqvist. They were reliable, rapid, easy to perform and validate because the progress curve of each reaction rate can be continuously monitored. The method described has also been applied to human intestinal mucosa (Caco-2 cells).

Interassay calibration as a major contribution to the comparability of results in clinical enzymology

OBJECTIVE

Factors contributing to the applicability of interassay calibration of methods measuring enzyme catalytic activities are described. Also discussed are the properties essential for such a material. Similarity of specificity for the methods to be calibrated as well as commutability between the material(s) intended to be used as calibrator are the main criteria to be satisfied.

RESULT

Several examples demonstrated that interassay calibration is feasible but a multi-enzyme calibrator with a wide commutability for the most popular methods remains to be developed. This is the project of the IFCC Working Group on Calibrators in Clinical Enzymology (WG-CCE). Several experimental data are also presented that indicate that the temperature at which the reaction is carried out is not a limiting factor in the implementation of interassay calibration in clinical enzymology.

Validation of an enzyme calibrator--an IFCC guideline. International Federation of Clinical Chemistry

OBJECTIVES

The objective of this guideline is to improve standardization in clinical enzymology in order to improve intermethod comparability of patients' results.

DESIGN AND METHODS

The reference system, combination of the reference method and the reference material, is used to produce a reference value for a given catalytic activity. Sets of methods are formed of methods exhibiting the same analytical specificity. Materials intended to be used as enzyme calibrators are experimentally checked for their commutability.

RESULTS

The transfer of accuracy from the reference value to patients' results is dependent on methods (analytical specificity) and on materials (experimentally assessed commutability). The feasibility of this approach was demonstrated with materials of high level for several enzymes and for each of them for several routine methods.

CONCLUSION

Expected advantages of this approach in clinical enzymology are presented.

Brassiodol, a new iodised oil for goitrous patients

A new iodised oil, called Brassiodol, is proposed to prevent or eradicate 127I-deficiency disorders. Its original synthesis utilises rapeseed oil as vehicle of iodination, allowing the covalent binding of 127I atoms to all olefin groups of fatty acids (FAs). The final product contains 376 mg 127I/mL, manifests high refractoriness to degradative processes and is well tolerated by goitrous patients. The proposed dosage is 1 mL/year in adults owing to the rapid deiodination and massive 127I leakage of larger amounts in the urinary output. About 300-350 mg 127I may undergo tissue sequestration, insuring appropriate iodine coverage during 9-12 months. Clinical follow-up, hormonal data, and 127I excretory kinetics point to the normalisation of thyroid function within 3 months is stages I and II of the goitrous disease. This iodised oil, characterised by low cost, easy handling and high nutritional efficiency, seems ideally suited to meet public health and economical problems in countries facing severe goitrous areas.

Iodised rapeseed oil for eradication of severe endemic goitre

Iodised oil is traditionally based on the fatty acids (FAs) of the poppyseed, an expensive commodity. An equipotent but cheaper vehicle would be welcome. Iodination of rapeseed oil yields a product (Brassiodol) with a total iodine content of 376 mg/mL. Brassiodol has been compared with the poppyseed-based Lipiodol in two villages in Chad in the west African goitre belt. A 2 mL dose of Brassiodol is followed by urinary spillover of half the ingested iodine. The other half undergoes tissue sequestration and slow release, allowing protection against iodine deficiency for 9 months and regression of stage I/II goitre for longer than was achieved with Lipiodol. The prolonged protection offered by Brassiodol can be attributed to its unique lipid profile. The urinary output argues that 1 mL should not be exceeded, and at that dose the cost would be only 20 US cents per person per year.

Incomplete or absent acute phase response in some postoperative patients

In a prospective study, 74 patients were admitted for an open fracture of the lower limb and treated by osteosynthesis. None of them presented infectious complication during the postoperative period. Among them, 67 exhibited a classical acute phase response. In 5 patients, the response was apparently incomplete since no serum C-reactive protein (CRP) rise was observed after the injury; i.e. CRP concentrations remained inferior to the detection limit of the assay used; in contrast, serum alpha-1 acid glycoprotein (AAG) concentrations were temporarily increased, a variation associated with a concomitant decrease of transthyretin (TTR) concentration. In 2 other patients, CRP and AAG levels were not significantly modified. The 7 patients did not suffer hepatic insufficiency or protein malnutrition. In our series, incomplete or absent acute phase response was not rare (prevalence 9%) and was not related to an increased risk of postoperative infection. In contrast to CRP, the TTR response, i.e. a transitory decrease, was observed in all the 7 patients.