La standardisation en enzymologie clinique a debute, il y a plus de vingt ans, avec le developpement, par la Federation internationale de chimie clinique (IFCC), de methodes de reference. Diverses methodes recommandees ont ete egalement elaborees dans plusieurs pays. Ces methodes (notamment les methodes de reference), decrites selon un mode operatoire manuel, sont parfois contraignantes ou difficiles a adapter sur les automates. C'est la raison pour laquelle elles sont peu utilisees en pratique courante. Le developpement, par les industriels, de coffrets reactifs dont la composition se rapproche de celle definie dans les methodes de reference ou recommandees ne resout pas les problemes de standardisation. Ainsi, les efforts pour ameliorer la coherence intertechnique des resultats par la standardisation des methodes, n'ont pas ete totalement couronnes de succes. Par ailleurs, les progres concernant l'appareillage et les reactifs ont surtout permis d'ameliorer la precision des mesures, mais ils ont aussi entraine une diversification des techniques de mesure utilisees dans les laboratoires. Il s'ensuit que, dans le domaine de l'enzymologie clinique, les resultats des laboratoires sont peu transferables d'un laboratoire a un autre contrairement aux recommandations du Guide de bonne execution des analyses [1]. Pour corriger ces effets, certains proposent ou utilisent des facteurs de conversion. Ces facteurs de conversion sont destines a transformer des resultats obtenus par une technique en ce qu'ils auraient ete dans d'autres conditions operatoires. L'exemple le plus frequent concerne la temperature de mesure, celle-ci etant le plus souvent 37 °C, alors que les methodes de reference preconisent de mesurer les activites enzymatiques a 30 °C. Il faut souligner que l'effet de la temperature sur la cinetique enzymatique depend non seulement de l'enzyme, mais aussi du systeme analytique employe (reactifs et qualite de l'appareillage). C'est pourquoi, des 1990, la SFBC a recommande qu'aucun facteur de transformation intertemperature ne soit employe [2, 3].

La standardisation en enzymologie clinique a debute, il y a plus de vingt ans, avec le developpement, par la Federation internationale de chimie clinique (IFCC), de methodes de reference. Diverses methodes recommandees ont ete egalement elaborees dans plusieurs pays. Ces methodes (notamment les methodes de reference), [...]

La technique selectionnee par la SFBC pour le dosage de la creatinine serique et (ou) plasmatique est basee sur la mesure en methode cinetique de la reaction de coloration fournie par la creatinine avec le picrate alcalin, sans traitement prealable du specimen biologique. Les differents facteurs intervenant dans la reaction sont etudies en fonction de leur influence sur la qualite des resultats obtenus notamment avec des specimens comportant des substances susceptibles d'interferer. La concentration de chacun des reactifs, le rapport de dilution du specimen, la duree de la mesure et le mode de calibrage ont ete etudies de facon systematique pour minimiser l'interference de bilirubine, de glucose, d'acetoacetate dans le specimen biologique et obtenir une technique presentant une sensibilite optimale. Les concentrations (dans le test) retenues sont de 150 mmol/L d'hydroxyde de sodium, 10 mmol/L d'acide picrique et 2 g/L de lauryl sulfate de sodium. Une solution de BRIJ 30% (vol/vol) est ajoutee a raison de 10 mL par litre de reactif. Les conditions operatoires selectionnees sont pour la fraction volumique du specimen : de 0,07 a 0,08, pour la longueur d'onde : 505 a 510 nm, pour la temperature : 37 °C et pour la duree de l'incubation du specimen avec le reactif alcalin, avant addition d'acide picrique : 5 minutes au minimum. La matrice du calibrateur utilise doit etre proteique. Le calibrage est effectue a l'aide d'un serum titre. La premiere mesure est realisee 20 a 40 secondes apres le debut de la reaction. La duree de la mesure est comprise entre 120 et 150 secondes.

A selected method for the determination of creatinine in plasma, using the reaction with alkaline picrate without prior pretreatment has been proposed by the Commission 'Validation de techniques' in the SFBC (Société Française de biologie clinique). The transferability step was conducted in seven laboratories, equipped with different automatic analyzers, using analytical procedures derived from the recommended method. Its goal was to test whether the original analytical performances could be maintained and consistent results obtained. The validation step was designed to evaluate the linearity limits of the analytical range, the detection limit, to assess accuracy as compared to a high performance liquid chromatography and to investigate the effect of the main interferents. Linearity limits are 15 and 2000 mumol/L. The detection limit is 3 to 8 mumol/L according to the analytical systems. The selected method can fulfil the set imprecision goals: intralaboratory CV minus than 2% (within-run), minus than 4% (run-to-run), interlaboratory CV minus than 5% (for 100 mumol/L creatinine). Inaccuracy evaluated for the chosen control sera is 1 to 15% as compared to the chromatographic method, according to the sera and to the analytical systems. The results obtained with the selected method are more consistent with the HPLC than are those obtained with an alkaline picrate method without SDS or with an enzymatic method. No interference could be demonstrated for acetoacetate (up to 8 mmol/L), hemoglobin (up to 210 mumol/L), unconjugated bilirubin (up to 250 mumol/L), glucose (up to 30 mmol/L), IgG (up to 45 g/L), albumin (up to 60 g/L). The effect of cephalosporins depends on the molecule. The reagents are stable for at least 6 months when stored in closed vials at +20 degrees C. The alkaline reagent is stable 30 days at +4 degrees C. Reference limits (0.025 and 0.975 fractiles) have been established for healthy adults. They are respectively 73 to 126 mumol/L for men and 59 to 100 mumol/L for females.

The method selected by the SFBC (Société française de biologie clinique) is derived from the colorimetric reaction of creatinine with alkaline picrate, measured kinetically, without any pretreatment step. The key parameters of the reaction determining the quality of the results are studied, with special regard to samples including known interferents. The aims of the study were to gain an optimal analytical sensitivity and to reduce main interferences (acetoacetate, bilirubine, glucose, protein) which plague the Jaffé reaction, through a comprehensive study of the reagents, of their concentrations and of the analytical procedures. The selected concentrations (in the test) are: 150 mmol/L sodium hydroxide, 10 mmol/L picric acid and 2 g/L sodium dodecyl sulfate. Ten millilitres of a BRIJ solution (30% volvol) are added to the reagent. The operating procedures are as follow: sample ratio 0.07 to 0.08; wavelength 505 to 510 nm; temperature 37 degrees C; incubation of the specimen with the alkaline reagent 5 mn (at least), before starting the reaction with picric acid. A seric calibrator is recommended. The first measurement is taken 20 to 40 s after starting the reaction. Total measurement time is 120 to 150 seconds.

A selected method for the determination of creatinine in plasma, using the reaction with alkaline picrate without prior pretreatment has been proposed by the Commission 'Validation de techniques' in the SFBC (Societe Francaise de biologie clinique). The transferability step was conducted in seven laboratories, equipped with different automatic analyzers, using analytical procedures derived from the recommended method. Its goal was to test whether the original analytical performances could be maintained and consistent results obtained. The validation step was designed to evaluate the linearity limits of the analytical range, the detection limit, to assess accuracy as compared to a high performance liquid chromatography and to investigate the effect of the main interferents. Linearity limits are 15 and 2000 mu mol/L. The detection limit is 3 to 8 mu mol/L according to the analytical systems. The selected method can fulfil the set imprecision goals: intralaboratory CV minus than 2% (within-run), minus than 4% (run-to-run), interlaboratory CV minus than 5% (for 100 mu mol/L creatinine). Inaccuracy evaluated for the choosen control sera is I to 15% as compared to the chromatographic method, according to the sera and to the analytical systems. The results obtained with the selected method are more consistent with the HPLC than are those obtained with an alkaline picrate method without SDS ol with an enzymatic method. No interference could be demonstrated for acetoacetate (up to 8 mmol/L), hemoglobin (up to 210 mu mol/L), unconjugated bilirubin (up to 250 mu mol/L), glucose (up to 30 mmol/L), IgG (up to 45 g/L), albumin (up to 60 g/L). The effect of cephalosporins depends on the molecule. The reagents are stable for at least 6 months when stored in closed vials at +20 degrees C. The alkaline reagent is stable 30 days at +4 degrees C. Reference limits (0.025 and 0.975 fractiles) have been established for healthy adults. They are respectively 73 to 126 mu mol/L for men and 59 to 100 mu mol/L for females.

La presente etude multicentrique est consacree a l'alpha-Amylase (AMY), la gamma-Glutamyltransferase (GGT) et la Phosphatase alcaline (PAL). Elle montre que les resultats en enzymologie, obtenus dans des conditions de pratique courante, restent tres dependants des techniques employees. Les auteurs demontrent qu'il n'est pas possible d'employer, pour une enzyme donnee, un facteur constant pour transformer les resultats obtenus a une temperature en resultats qui auraient ete obtenus a une autre temperature. De plus, la comparaison des resultats a la limite superieure des valeurs de reference ne corrige pas toujours la dispersion intertechnique. Par contre, l'emploi de materiaux de reference comme calibrateurs permet de reduire considerablement cette dispersion. Cette approche s'est revelee applicable pour les 3 enzymes et pour la plupart des techniques testees. D'une facon generale, il est necessaire que les preparations utilisees comme calibrateurs d'enzymes contiennent des enzymes presentant la meme reactivite que celles presentes dans les specimens provenant de patients. Le fait que l'essai ait ete concluant avec une enzyme pour laquelle les differences intertechniques sont considerables (AMY) indique que l'approche de l'etalonnage des mesures d'activite enzymatique est tres generale et efficace. Le developpement par les industriels du bioreactif de multicalibrateurs d'enzymes, valides pour les techniques les plus frequemment utilisees, nous parait urgent.

We report here on the results of a multicenter study of three enzyme activities (gamma-glutamyltransferase, alkaline phosphatase and amylase). For each activity, measurements were performed in two laboratories on different series of patients' specimens under routine conditions, at 30 and 37 degrees C, with techniques frequently used in France and with the IFCC reference method, when it exists. For each technique, precision was acceptable, but results differed considerably according to the technique used. The study also showed that for different techniques it is not possible to use a single transformation factor for activities between 30 and 37 degrees C. Patients' results determined by two techniques often showed a constant relationship. Groups of techniques that determined the same catalytic activity in patients' specimens were identified, whereas other techniques did not have this property. Several preparations, including reference materials produced by the Community Bureau of Reference (European Community, Brussels) and ten commercial secondary materials were tested for similar behaviour as compared to patients' samples. Results show the commutability of reference materials within a group of techniques indicating that they can be used as calibrators. This was seldom the case for the commercial secondary materials and we did not find any such material suitable for calibration of the three enzymatic activities. The present study demonstrates that with defined techniques and validated calibrators it is possible to reduce considerably differences between results obtained with different techniques at different temperatures and in different laboratories.

We report the results of a national quality-control survey on glycohemoglobin (GHb), monitored in France by the Société Française de Biologie Clinique on behalf of the authority of the "Agence du Médicament." A sample of lyophilized hemolysate was sent to 3109 laboratories. Results were obtained from 2770 laboratories. HbA1C, HbA1, and total GHb were measured by 50%, 24%, and 26% of the participants, respectively. Of these measurements, 79% of the HbA1C results and 76% of the total GHb results, but only 48% of the HbA1 results, were within the +/- 20% limits of the indicated target values. Mean values for the hemolysate ranged from 8% to 11% for HbA1C, from 7% to 12% for HbA1, and from 11% to 13% for total GHb. The interlaboratory CVs ranged from 3% to 20%, according to method used. So, methods used for GHb assay, which are based on various principles, exhibit very different analytical performances. Nonetheless, this large-scale study indicates that some techniques can support transferability of results from laboratory to laboratory.

alpha-Amylase, alkaline phosphatase and gamma-glutamyltransferase were studied in a multicentre evaluation. Analyses were performed on different patient samples. Each enzyme was assayed in two different laboratories at both 30 and 37 degrees C, with widely used reagent kits and with the IFCC reference method (if in existence). Results differed considerably according to the measurement procedure. Data also showed that it was not possible to employ a constant conversion factor for one enzyme and different techniques between 30 and 37 degrees C. Calibration with three reference materials extensively improved the intermethod consistency for most of the tested measurement procedures. It was possible to transfer accuracy from the method used for the certification of the reference material to routine procedures, by using the reference material as calibrator. Temperature did not seem to be a crucial variable for the implement of the enzyme calibrator approach.

Early recognition of infantile asthma in wheezing infants is a major problem for physicians. We investigated whether detection of early sensitization to inhalant allergens would be useful to identify those wheezing infants who are likely to develop asthma. A total of 67 infants (aged 1-25 months) hospitalized For a wheezing episode were initially tested for reactivity to inhalant allergens by both skin prick test and in vitro measurement of specific IgE antibodies (Phadiatop(R)). Thirty-seven of the infants were already considered to have infantile asthma, and 30 presented only their first or second wheezing episode when included in the study. All infants were followed for a mean period of 18 months. Seventeen (25 %) infants, including seven infants initially not asthmatic, had positive prick test to Dermatophagoides pteronyssinus or to cat fur. All of these children were diagnosed as suffering from infantile asthma at the end of the follow-up. Thus, skin test positivity to inhalant allergens was significantly associated with the diagnosis of infantile asthma (P<0.05) and could be considered to be predictive of the development of infantile asthma (P<0.03). In contrast, Phadiatop was less sensitive than skin prick tests, and only five children had positive in vitro test results, suggesting that specific IgE may primarily bind to tissue mast cells before being detectable in serum. We concluded that sensitization to inhalant allergens may distinguish wheezing infants who develop asthma from those who do not, and that skin testing may assist the early diagnosis of asthma in wheezing infants.

During a multicenter evaluation, 16 methods for creatinine measurement have been tested according to the guidelines of the Société française de biologie clinique (SFBC) protocol. Kinetic Jaffé methods, widely used in France, performed on different analytical systems (Astra Beckman, IL 508, RA 1000 Technicon, Hitachi 704, 705, 717 Boehringer, Fara Roche, Progress Kone, Kem-O-Mat Coulter, Perspective France Monitor) have been compared to a continuous flow method with aqueous standards, to enzymatic methods using creatinine amidohydrolase with a colorimetric measurement (Boehringer and Ektachem Kodak) and to an HPLC method. Reproducibility, estimated with four different control sera, proved to be unsatisfactory in some cases as compared to current criteria for imprecision (less than +/- 10 mumol/l for intralaboratory and less than +/- 20 mumol/l for interlaboratory imprecision). The same selected patients sera covering the whole range of physiopathological concentrations have been analyzed with each method, and compared with the continuous flow results. Differences are more dependent on the sample than on the calibrators. The influences of haemolysis, bilirubin, acetoacetate, albumin, lipids, glucose, and some cephalosporins have been evaluated with spiked human sera. Haemolysed, turbid and jaundiced patient samples have been analyzed as well. The results vary according to the analytical procedure. This study took place in the implementation of a selected method for routine purpose with special regards to interferences and an acceptable imprecision. The method must satisfy the physicians' demands in the renal function exploration, especially in kidney-transplant patients.

Journal Article Direct Methods vs Blanking Methods for Iron-Determination: Effect of Serum Turbidity Get access M Delespine, M Delespine Lab. de Biochim. A, Hôpital Necker, Paris, France Search for other works by this author on: Oxford Academic Google Scholar D Labbe, D Labbe Lab. de Biochim. A, Hôpital Necker, Paris, France Search for other works by this author on: Oxford Academic Google Scholar H T Phung, H T Phung Lab. de Biochim. A, Hôpital Necker, Paris, France Search for other works by this author on: Oxford Academic Google Scholar A Vassault, A Vassault Lab. de Biochim. A, Hôpital Necker, Paris, France Search for other works by this author on: Oxford Academic Google Scholar M Bailly M Bailly Lab. de Biochim. A, Hôpital Necker, Paris, France Search for other works by this author on: Oxford Academic Google Scholar Clinical Chemistry, Volume 38, Issue 5, 1 May 1992, Pages 782–783, https://doi.org/10.1093/clinchem/38.5.782a Published: 01 May 1992

During a multicenter evaluation, 16 methods for creatinine measurement have been tested according to the guidelines of the Societe francaise de biologie clinique (SFBC) protocol. Kinetic Jaffe methods, widely used in France, performed on different analytical systems (Astra Beckman, IL 508, RA 1000 Technicon, Hitachi 704, 705, 717 Boehringer, Fara Roche, Progress Kone, Kem-O-Mat Coulter, Perspective France Monitor) have been compared to a continuous flow method with aqueous standards, to enzymatic methods using creatinine amidohydrolase with a colorimetric measurement (Boehringer and Ektachem Kodak) and to an HPLC method. Reproducibility, estimated with four different control sera, proved to be unsatisfactory in some cases as compared to current criteria for imprecision (less than +/- 10 mumol/l for intralaboratory and less than +/- 20 mumol/l for interlaboratory imprecision). The same selected patients sera covering the whole range of physiopathological concentrations have been analyzed with each method, and compared with the continuous flow results. Differences are more dependent on the sample than on the calibrators. The influences of haemolysis, bilirubin, acetoacetate, albumin, lipids, glucose, and some cephalosporins have been evaluated with spiked human sera. Haemolysed, turbid and jaundiced patient samples have been analyzed as well. The results vary according to the analytical procedure. This study took place in the implementation of a selected method for routine purpose with special regards to interferences and an acceptable imprecision. The method must satisfy the physicians' demands in the renal function exploration, especially in kidney-transplant patients.

Dans le cadre de l'exploration biologique de l'atopie chez des enfants (n = 44) présentant des troubles respiratoires, le dosage dans le sérum des IgE totales et des IgE spécifiques de cinq allergènes courants (d1, d2, e1, g3, g6) a été réalisé par une technique utilisant la chimiluminescence : Magic Lite (Ciba Corning). Les résultats obtenus pour les IgE spécifiques ont été confrontés d'une part aux résultats d'une technique radio-isotopique : rast Pharmacia et, d'autre part, aux tests cutanés. Dans 93% des cas, une concordance des résultats exprimés en classe (avec une tolérance d'une classe d'écart) est constatée entre les deux techniques. Les tests cutanés pratiqués (n = 22) confirment les résultats des dosages d'IgE spécifiques dans 18 cas. La technique Magic Lite est rapide (moins de 2 h) et ne nécessite que 25 μl de spécimen par allergène testé.