PubMed Health⌕ Search

Biomedical subjects

G Férard

Publications and source records attributed to G Férard.

At least 19 recordsLinked to original sources
PubMed2003

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.

Adult↗
PubMed2001

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.

Adenosine Deaminase↗
PubMed1999

[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.

Adolescent↗
PubMed1998

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.

Calibration↗
PubMed1998

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.

Calibration↗
PubMed1998

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.

Calibration↗
PubMed1998

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.

Adolescent↗
PubMed1997

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.

Adult↗
PubMed1997

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.

Acute-Phase Reaction↗
PubMed1996

Diagnostic value of C-reactive protein and transthyretin in bone infections of the lower limb.

In a prospective study, white and red blood cell counts, hematocrit, erythrocyte sedimentation rate (ESR), albumin, alpha-1 acid glycoprotein, C-reactive protein (CRP), and transthyretin (TTR) values were determined by serial measurements during 23 days in 80 patients with an open fracture of the lower limb. Postoperative reference profiles were defined in 74 patients without septic complications. In the six remaining patients, serum CRP and TTR concentrations were found efficient for the early diagnosis of postoperative infections: a CRP/TTR mass concentration ratio higher than 0.6 from the 8th day after surgery was sensitive (100%) and specific (93%). Variations of CRP and TTR concentrations often preceded the clinical diagnosis in patients with early infection. ESR was found unreliable with regard to postoperative infection because of its high dependence with respect to red blood cell count.

Adolescent↗
PubMed1996

Catalytic properties and stability of lipase purified from human pancreatic juice.

Catalytic properties of a preparation of human pancreatic lipase purified from pancreatic juice have been compared to those of the enzyme present in pooled plasma from patients suffering from acute pancreatitis. They were very similar as regards influence of effectors (sodium deoxycholate, colipase and Ca2+), optimal pH and apparent KM in optimized conditions. The stability of the preparation appeared to be satisfactory. It was found to be stable for at least 200 days in a liquid form at +4 degrees C and predictive degradation rates per year of the lyophilized form at +4 degrees C and -20 degrees C were 0.06% and 0.00%, respectively. The close similarity of properties of this preparation with those of a recombinant human pancreatic lipase produced in V79 Chinese hamster lung cells suggests that both approaches (purification from human pancreatic juice and gene transfer technology) could be used to produce a suitable reference material for this enzyme.

Calcium↗
PubMed1996

Importance of standardization of lipase assays by using appropriate calibrators.

Comparability of lipase catalytic activities was poor when lipase was determined in 50 patients' specimens by a turbidimetric (Boehringer) and a colorimetric (Sigma) assay. Mean values of results differed by a ratio of 2.39. Optimal common conditions were defined for the titration of lipase activity in two commercial calibrators and in a home-purified preparation of human pancreatic lipase (HPL). When using these titers for each calibrator, comparability was greatly improved (ratio = 1.25). This result indicates that a significant part of between-method discrepancy is due to the lack of a reference method for the titration of lipase calibrators. Intermethod behavior of each material was compared with that of patients' specimens. By using HPL as calibrator, comparability was still dramatically improved (ratio = 1.01). This study shows the importance of the validation of a material for defined routine measurement procedures, before its use as calibrator.

Calcium↗
PubMed1995

Usefulness of reference materials in calibration of enzyme activities.

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.

Alkaline Phosphatase↗
PubMed1995

[Improvement of result coherence in clinical enzymology: multicenter study of gamma-glutamyltransferase, alkaline phosphatase and amylase activities].

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.

Alkaline Phosphatase↗
PubMed1995

[Effects of pooling biological specimens on the results of medical biological analysis].

The reasons of pooling biological specimens and the consequences of this approach are presented here. Pools are used to prepare lots of control sera or of reference solutions. Specimens are also mixed in order to detect some analytical interferences. Pooling of biological specimens from several subjects and analysis of this pool instead of the measurement of each specimen is not acceptable because it induces a dilution of the specimen to be assayed and thus potentially false negative results. Another aspect is that dilution is performed with specimens of unknown composition. Particularly, these specimens may contain interferent substances, inducing analytical errors. These arguments are relevant in the different sciences of medical biology and for qualitative and quantitative tests.

Biological Products↗
PubMed1995

[1995: a decisive progress for the interlaboratory transferability of results by using enzyme and protein reference materials].

Transferability of results in clinical enzymology and immunochemistry may be improved by using validated calibrators. For that purpose, certified reference materials (CRM) have been developed. Authors emphasize the need to make known and to use these tools properly, and on the potential efficiency of this approach in immunochemistry with CRM 470, certified for 14 plasma proteins and with enzyme CRMs produced at the international level. They recall the necessity to validate calibrators for specified techniques of measurement used in routine. They also indicate that this approach, if properly conducted, should allow to ensure the transferability of results in enzymology and immunochemistry and thus the clinical efficiency of laboratory results.

Enzymes↗